# Cleaning/Sanitizing fresh water holding tanks



## Langlo06 (Oct 28, 2011)

As springtime seems to be amongs us, looking over the to do list and
cleaning/sanitizing fresh water holding tanks is something that gets 
negleted almost every year except this year.

Any suggestion as to best practice to use


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## smurphny (Feb 20, 2009)

I put an additional access plate in my water tank so I can get right in there and scrub it out 100% with bleach before refilling. It also probably wouldn't hurt to get a pressure washer in there. In any case, my first fill of water gets a large dose of chlorine to make sure any microorganisms are eliminated.


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## pdqaltair (Nov 14, 2008)

I'm working on something for Practical Sailor right now. How is it, do you suppose, that the glycol-side of office building AC systems are kept sterile? Hint: no toxic chemicals or biocides are required.

Put another way, it is simple to avoid the whole problem, you just need to think like a bug. What does a bug need? How do you preserve food?


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## Don L (Aug 8, 2008)

pdqaltair said:


> I'm working on something for Practical Sailor right now. How is it, do you suppose, that the glycol-side of office building AC systems are kept sterile? Hint: no toxic chemicals or biocides are required.


By maintaining a high glycol level


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## TerryBradley (Feb 28, 2006)

Hmm. Never gave much thought to it. Raised on well water. Drank out of half the Lakes in Canada. Just fill my water tanks from the marina and drink it and cook with it. I have to admit I have looked down into the tanks just to see if there's anything growing or crawling around in there but so far after four years I haven' t seen anything and haven't incurred any uh, er, shall we say; "intestinal disorders".


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## pdqaltair (Nov 14, 2008)

Don0190 said:


> By maintaining a high glycol level


Or dry.

Yup, just about that simple.


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## Don L (Aug 8, 2008)

pdqaltair said:


> Or dry.
> 
> Yup, just about that simple.


The problem with "dry" if you used glycol to layup the lines is that there will be a trace level left behind. As a water treater I will tell you nothing causes me more problems in water loops that low level trace glycol!


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## pdqaltair (Nov 14, 2008)

Don0190 said:


> The problem with "dry" if you used glycol to layup the lines is that there will be a trace level left behind. As a water treater I will tell you nothing causes me more problems in water loops that low level trace glycol!


Exactly.


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## Multihullgirl (Dec 2, 2010)

From Peggie Hall, who does know what she is talking about:

"Although most people think only in terms of the tank, the plumbing is actually the source of most foul water, because the molds, mildew, fungi and bacteria which cause it thrive in damp dark places, not under water. Many people—and even some boat manufacturers—believe that keeping the tanks empty reduce the problem, but an empty water tank only provides another damp dark home for those “critters.” 

There are all kinds of products sold that claim to keep onboard water fresh, but all that’s really necessary is an annual or in especially warm climates, semi-annual recommissioning of the entire system—tank and plumbing. The following recommendations conform to section 10.8 in the A-1 192 code covering electrical, plumbing, and heating of recreational vehicles (which includes boats). The solution is approved and recommended by competent health officials. It may be used in a new system a used one that has not been used for a period of time, or one that may have been contaminated. 

Before beginning, turn off hot water heater at the breaker; do not turn it on again until the entire recommissioning is complete. 

Icemakers should be left running to allow cleaning out of the water feed line; however the first two buckets of ice—the bucket generated during recommissioning and the first bucketful afterward--should be discarded. 

1. Prepare a chlorine solution using one gallon of water and 1/4 cup (2 oz) Clorox or Purex household bleach (5% sodium Hypochlorite solution ). With tank empty, pour chlorine solution into tank. Use one gallon of solution for each 5 gallons of tank capacity. (Simpler way to calculate: 1 quart bleach/50 gal water tank capacity)

2. Complete filling of tank with fresh water. Open each faucet and drain **** until air has been released and the entire system is filled. Do not turn off the pump; it must remain on to keep the system pressurized and the solution in the lines 

3. Allow to stand for at least three hours, but no longer than 24 hours.

4 Drain through every faucet on the boat (and if you haven't done this in a while, it's a good idea to remove any diffusion screens from the faucets, because what's likely to come out will clog them). Fill the tank again with fresh water only, drain again through every faucet on the boat. 

5. To remove excess chlorine taste or odor which might remain, prepare a solution of one quart white vinegar to five gallons water and allow this solution to agitate in tank for several days by vehicle motion. 

6. Drain tank again through every faucet, and flush the lines again by fill the tank 1/4-1/2 full and again flushing with potable water.

An annual or semi-annual recommissioning according to the above directions is all that should be necessary to keep your water tasting and smelling as good as anything that comes out of any faucet on land. If you need to improve on that, install a water filter. Just remember that a filter is not a substitute for cleaning out the system, and that filters require regular inspection and cleaning or replacement.
To keep the water system cleaner longer, use your fresh water...keep water flowing through system. The molds, fungi, and bacteria only start to grow in hoses that aren't being used. Before filling the tank each time, always let the dock water run for at least 15 minutes first...the same critters that like the lines on your boat LOVE the dock supply line and your hose that sit in the warm sun, and you certainly don't want to transfer water that's been sitting in the dock supply line to your boat's system. So let the water run long enough to flush out all the water that's been standing in them so that what goes into your boat is coming straight from the water main. 

Finally, while the molds, fungi and bacteria in onboard water systems here in the US may not be pleasant, we're dealing only with aesthetics...water purity isn't an issue here--or in most developed nations...the water supply has already been purified (unless you're using well-water). However, when cruising out of the country, it's a good idea to know what you're putting in your tanks...and if you're in any doubt, boil all water that's to be drunk or used to wash dishes, and/or treat each tankful to purify. It's even more important in these areas to let the water run before putting it in the tank, because any harmful bacteria will REALLY proliferate in water hoses left sitting on the dock.
__________________
Peggie Hall--Specializing in marine sanitation since '87 
Author "Get Rid of Boat Odors-- A Guide to Marine Sanitation Systems & Other Sources of Aggravation"


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## chef2sail (Nov 27, 2007)

We follow Peggys method twice a year and never have had a problem.. Is not recommended I think with metal water tanks though.


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## Multihullgirl (Dec 2, 2010)

I don't think it matters whether it's metal or plastic. Mine are steel and bleach has been ok. Acid, not so much. Don't ask how I know


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## christian.hess (Sep 18, 2013)

good ole bleach

plus a cap full every full tank


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## miatapaul (Dec 15, 2006)

Multihullgirl said:


> I don't think it matters whether it's metal or plastic. Mine are steel and bleach has been ok. Acid, not so much. Don't ask how I know


Yea steel should be ok, but Aluminum does not like bleach. I think for a problem system I might be wiling to use it, but not necessarily annually. Most hot water tanks are aluminum as well. (Rariton/Kuuma/Torrid/Seaward/West Marine)


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## kwaltersmi (Aug 14, 2006)

Our dock neighbor pours in a gallon of cheap vodka at the start of the season. Not sure it sanitizes/sterilizes anything, but he sure has a good time drinking from the galley sink for a few days.


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## pdqaltair (Nov 14, 2008)

kwaltersmi said:


> Our dock neighbor pours in a gallon of cheap vodka at the start of the season. Not sure it sanitizes/sterilizes anything, but he sure has a good time drinking from the galley sink for a few days.


That is provably a COMPLETE waste of money and a COMPLETE FALLACY. Ethanol is only a sterilizing agent above ~ 20% (look it up, and doesn't wine go funky?). What he is doing will only aggravate the problem, since fungus and bacteria consider weak alcohol good food, like sugar. See also post #7.

Basic observation, folks. Let's not start an urban legend.


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## Don L (Aug 8, 2008)

kwaltersmi said:


> Our dock neighbor pours in a gallon of cheap vodka at the start of the season. Not sure it sanitizes/sterilizes anything, but he sure has a good time drinking from the galley sink for a few days.


must be about a 2 gallon water tank


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## Multihullgirl (Dec 2, 2010)

I'm not sure I'm buying that the relatively low concentrations of bleach that Ms Hall suggests, especially for the short period suggested, would hurt aluminium tanks either. Sure, high concentrations for extended periods wouldn't be good, as bleach is fairly corrosive.

Keep in mind that chlorine is in most all municipal systems in the States, so if you fill from city water, you're probably getting a dose.


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## gamayun (Aug 20, 2009)

Multihullgirl said:


> snip...
> 
> Before filling the tank each time, always let the dock water run for at least 15 minutes first...


I've used the Peggy Hall method to get rid of the "old" taste in the tanks, but since I use the tank water often, it's no longer a problem. Generally water straight out of the tap is good. Or you could switch to a clean water hose that doesn't sit on the dock every day. I think us civilized people tend to get a little squeamish about sanitation when our guts can handle most things we throw its way. I do take exception about letting dock water run for at least 15 minutes (which seems WAY too long). Most of the world is literally dying for the amount of clean water that we waste without a thought. Please wash your boat or do something useful and don't let it drain into the harbor. It drives me crazy to watch a free flowing faucet, especially with increasing droughts around the world.

OK, I'm off my soapbox now


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## Multihullgirl (Dec 2, 2010)

There's no reason why when you're letting the water run for the 15 mins that you can't wash your boat down in some way... I'm sorry, I thought that went without saying. Thanks, gamayun


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## pdqaltair (Nov 14, 2008)

Off topic warning.

IMHO, unless you are planning to ship water overseas, "droughts around the world" are an irrelevant rhetorical reference. It is a local condition, like cold. In many areas, we have more water than we want or need (flood warnings today), and all wasted water eventually runs down river.

California is different, with lots of development in an arid local.

----

That said, simple sanitation practices reduce waste. I flush very little due to avoiding infection.


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## Minnesail (Feb 19, 2013)

pdqaltair said:


> Off topic warning.
> IMHO, unless you are planning to ship water overseas, "droughts around the world" are an irrelevant rhetorical reference. It is a local condition, like cold. In many areas, we have more water than we want or need (flood warnings today), and all wasted water eventually runs down river.


It can be an *extremely* local condition. Here in Minneapolis we get our water out of the Mississippi River and we have more issues with flooding than with drought. But only 30 miles away the city of White Bear Lake gets their water from wells and the wells are running dry and the lake is disappearing.

But even if you are in a water rich area, conservation is a good idea. 15 minutes seems ridiculously long. I would think in most places you could tell when hose water is flushed out and the fresh water is flowing by the change in temperature.


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## tdw (Oct 2, 2006)

Please watch the OT posts. The thread topic is Water Tank Cleaning ... I appreciate that some, particularly those of you/us who live in drought effected lands, may find the idea of wasting water to be disturbing but it doesn't have anything to do with this thread.


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## Don L (Aug 8, 2008)

FYI - for those with aluminum tanks that are worried about the bleach (high levels not 1-2 ppm normal levels in city water) there is always hydrogen peroxide. You have to find a supplier for high strength not that stuff in the store. The peroxide is safer for the materials in the fresh water system, but not for you if you get it on yourself.

You can also use on plastic etc tanks.


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## Multihullgirl (Dec 2, 2010)

What concentration peroxide and what quantities? The peroxide used in hair bleaching varies from 20 to 40 percent, and those are available at beauty supply houses. The term they use is 'developer.'


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## jameswilson29 (Aug 15, 2009)

Langlo06 said:


> As springtime seems to be amongs us, looking over the to do list and
> cleaning/sanitizing fresh water holding tanks is something that gets
> negleted almost every year except this year.
> 
> Any suggestion as to best practice to use


After emptying the tanks, I pour in a several gallon jug of vinegar and run through the system, leaving the residue in the tank and hoses. Then I fill and flush the tank. During the season, I regularly fill and empty the tanks.


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## RichH (Jul 10, 2000)

There is a tremendous amount of myths and misinformation on the 'net' concerning boat water tankage/systems.

The essence here is to treat your water tank/system exactly like you do to your pots, pans, dishes, and glassware, etc. Hygiene / cleanliness is important. Once your boat water system develops 'bacteria slimes', etc. on the internal walls, the only effective way (without have a 'laboratory' do repeated 'cultures' of the water after repeated shock sanitizations) to remove this is by 'mechanical scrubbing' with soap and water, etc. To prevent such contamination you 'should' keep sufficient 'clorox' in the water so that you 'just barely smell the clorox' in the spigot water

I summarized the 'currrent' / state of the art in sanitization of water systems as used by municipal US water systems and which would be applicable for CURRENTLY USED boat water systems (not 'new' installations) in: http://www.sailnet.com/forums/gear-maintenance/67003-keeping-water-sweet-3.html .... see post #23.

High potency (high concentration) Hydrogen Peroxide and 'accelerated' peroxides .... stay away from them unless you really really KNOW how and have the expertise to use these potentially DANGEROUS chemicals that can do a LOT of harm to skin, eyeballs, and other necessary human parts. 
To sanitize a water system with 'drug store' hydrogen peroxide, youd need to totally fill the whole water system with 3% H2O2 and then let it sit/soak for several hours. Scrub brushes are infinitely faster and you can SEE what you are 'removing'.

;-)


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## denverd0n (Jun 20, 2008)

smurphny said:


> I put an additional access plate in my water tank so I can get right in there and scrub it out 100% with bleach...


Complete waste of good bleach. At concentrations above 20% you get absolutely no additional sanitation effect. The WHO recommends a 10% bleach solution for cleaning seriously contaminated water systems. Peggy Hall's recommendation of 1/4 cup per gallon of water is more than strong enough for all but the very worst contaminated of potable water tanks.

Edit: Hmmmm. And now that I reread that, I'm wondering if you didn't actually mean that you scrub it out with 100% bleach, but that you carefully scrub out 100% of the tank with a bleach solution. If I misunderstood then... Never mind.

In any case, I know that some people do think that if a quarter cup per gallon is good, then mixing it 50:50, or even stronger, must be better. Nope. As I said, any concentration above 20% bleach to 80% water is just a waste of bleach. 1/4th cup per gallon is more than enough. Personally, I use half that and have never had any problems at all (though I am careful to keep my tanks and system clean, so that I am never dealing with any serious issues).


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## RichH (Jul 10, 2000)

Standard practice for municipal potable water systems being shock sanitized, systems that are not visibly contaminated with biological slimes, would translate to 40 oz. Sodium Hypochlorite (5% 'clorox') per 100 gallons - a concentration of 10-15 parts per million of 'clorox', soak time is 1-2 hours, then flushed.
Maintenance dosage to retard contamination is ~1 ppm or about 4oz. (common laundry strength 5% bleach) per 100 gallons. 

Stagnant water systems such as 'boats' slowly 'use up' their chlorine, the chlorine continually reacting with tank, piping, etc. ... so, additional 'clorox' should be periodically added so that one can discern 'faintest' possible trace of the 'chlorine' in the water coming out a spigot.


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## Don L (Aug 8, 2008)

People really should stop being so lazy and cheap about how much treatment is in their tanks. While I have professional test equipment, you can go to the hardware or a pool store and get cheap test strips. Stop guessing and test the water!!!!


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## smurphny (Feb 20, 2009)

denverd0n said:


> Complete waste of good bleach. At concentrations above 20% you get absolutely no additional sanitation effect. The WHO recommends a 10% bleach solution for cleaning seriously contaminated water systems. Peggy Hall's recommendation of 1/4 cup per gallon of water is more than strong enough for all but the very worst contaminated of potable water tanks.
> 
> Edit: Hmmmm. And now that I reread that, I'm wondering if you didn't actually mean that you scrub it out with 100% bleach, but that you carefully scrub out 100% of the tank with a bleach solution. If I misunderstood then... Never mind.
> 
> In any case, I know that some people do think that if a quarter cup per gallon is good, then mixing it 50:50, or even stronger, must be better. Nope. As I said, any concentration above 20% bleach to 80% water is just a waste of bleach. 1/4th cup per gallon is more than enough. Personally, I use half that and have never had any problems at all (though I am careful to keep my tanks and system clean, so that I am never dealing with any serious issues).


Yes, that's what I meant. It actually takes a very small amount of Clorox in the water. I don't use anywhere near even 20%. More like 5%. Nothing like a physical scrubbing once in a while. The extra access also allows inspection in there behind the baffle up into the forward part of the tank which would be a mystery area without the access plate. I don't know why one was not installed there in the first place.
I have read that iodine is also a good sanitizer. Actually tried it in some drinking water once but had to dump it. It really has a bad taste.


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## denverd0n (Jun 20, 2008)

smurphny said:


> I have read that iodine is also a good sanitizer.


Iodine is an excellent sanitizer and has no effect on stainless steel or aluminum, both of which can have problems with bleach solutions that are too strong. The downsides of iodine are the staining, the cost (WAAAY more than bleach), and the fact that it requires more precise control of the rate of dilution.

The taste issue is probably just a matter of what you're familiar with. In developed countries nowadays, almost everyone has had--at one time or another--water where a trace of chlorine could be tasted. We're mostly familiar with that taste, somewhat used to it, and therefore accepting of it. Iodine, not so much.


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## outbound (Dec 3, 2012)

Have a whole boat water filtration system down to 4 microns. Works great and drink out of tap. Short money and worth it. Have two tanks integral to hull as all metal tanks eventually fail. Do the bleach thing once a season if boat laid up but afterward fill and empty tanks several times. Then use small amount of baking soda to get rid of bleach smell on last rinse. If boat being lived on and not on water restriction protocol ( e.g. passaging) use 2 caps of bleach per 100g tank. No smell. With fresh water flush on heads fair amount of water going through hoses regularly. Think hoses more likely than tanks to be the problem. When water restricted and heads turned to salt flush use more bleach. Thinking of putting pre filter in water fills as if nothing gets into tanks there is nothing to start growing but haven't thought it through yet. ? Has anyone done that and is it worth doing.


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## smurphny (Feb 20, 2009)

Pre-filtering is a great idea but probably not practical. Waiting for 80 gallons of water to filter at a fuel dock would have everyone waiting to come in ready to strangle you. We sailboats use so little fuel that I feel guilty taking an inordinate amount of time after pumping my 6 or so gallons of diesel when at a dock, especially if I'm next to a stinkpotter who just spent hundreds If tied up in a slip somewhere, I'd definitely be pre-filtering with a small micron unit. Of course, an automatic r.o. system would accomplish the same thing but they are power hogs. I have been thinking about putting in a low micron filter unit on my small manual pump to use just for drinking water, one that would take out microorganisms like giardia and the like. That would gain back the room taken up by storing extra water. Presently, I never drink from the main tank but carry 15 gallons of water I know is fresh and potable in 5 gallon containers.


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## Don L (Aug 8, 2008)

I always find it sad/interesting how many people are afraid to drink out of their water tanks! Maintain a free chlorine level in your tanks, ensure that you keep it pretty high by TESTING it, and then install a standard drinking water filter to use for the water you drink. Why do people want to make it so hard, aren't there more important things to worry about?


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## smurphny (Feb 20, 2009)

Don0190 said:


> I always find it sad/interesting how many people are afraid to drink out of their water tanks! Maintain a free chlorine level in your tanks, ensure that you keep it pretty high by TESTING it, and then install a standard drinking water filter to use for the water you drink. Why do people want to make it so hard, aren't there more important things to worry about?


Putting water in your tanks from sources you are not sure about (do you REALLY know about that dock system?) is an invitation to some serious diseases. I know a number of people who have contracted Giardia and I gotta tell you, I would not wish that on anyone! Water is generally safe to drink UNTIL IT ISN'T. Chlorine, yes but it cannot hurt to have a final filter on drinking water. Protozoa like Giardia are not easily killed by chlorine, chlorine dioxide yes but not household bleach.


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## Don L (Aug 8, 2008)

if you feel that way, why in the world would you put the water in your tanks????????


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## jameswilson29 (Aug 15, 2009)

Don0190 said:


> if you feel that way, why in the world would you put the water in your tanks????????


Primarily hand washing and dish washing. I use bottled water for my drinking water. There is a difference between drinking the water and using it for cleaning only.


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## outbound (Dec 3, 2012)

The other solution is use public sourced water when stateside with reliable source but reverse osmosis water when abroad. Have 4 50 g water tanks so expect to keep one in R.O. water only. Just have to remember to flip the levers back and forth. We carry bottled water but its only for emergency.
BTW- usually when we get diesel fill most of the 200g I can carry at one time. Only time we "top off" is just before a long trip. Still feel guilty so try to never do on week ends or other high traffic times.
SM 1+ on your advice. Appreciated and logical.


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## Multihullgirl (Dec 2, 2010)

From PRACTICAL SAILOR, October 2013:

"We’ve not yet tested products for water treatment, although that is on our radar for the near future. In past reports, we did look at water filters, including a December 1998 test and our Chandlery article on the Nature Pure QC2 in this issue. 

In your case, we’d recommend sanitizing your tanks and hoses first, rather than starting with a water filter or purifier. Most boat owners use hydrogen peroxide, a bleach-water solution, or a bleach-detergent-water solution. Some shy away from using bleach in aluminum water tanks because chlorine (bleach) is corrosive in large amounts. However, its effects are cumulative, so if you’re only using it on an occasional basis, it should be fine. (Annual freshwater-tank cleaning is recommended, or semi-annual in especially warm climates.) Rubber and neoprene water-pump parts are also vulnerable to damage when exposed to a lot of chlorine.

To sanitize your tanks, try the following procedure, which we gleaned from marine sanitation guru Peggy Hall, author of “Get Rid of Boat Odors: A Guide to Marine Sanitation Systems and Other Sources of Aggravation and Odor."

If the tank has a clean out/inspection port, look for anything that may be trapped around the baffle plates and the tank bottom. Swab away as much of this residue as possible. Then, to prep the system for cleaning, be sure to remove any filter cartridges or aerators at the sink faucet(s). If you have a water heater, turn it off at the electrical panel. Then, flush the system with potable water and drain it completely through each faucet. For cleaning, mix a chlorine-water solution using a quarter-cup (2 ounces) of Clorox or Purex household bleach per gallon of water; use one gallon of solution for each 5 gallons of tank capacity. Then pour the mixture into the empty tanks, and fill them the rest of the way with potable water. Run water from each faucet or outlet until air has been released and the entire system is filled. You will know when it’s filled because you will be able to smell bleach from the faucets. Do not turn off the water pump; it must remain on to keep the system pressurized and the solution in the lines. Leave the system pressurized with the bleach solution in it for at least three hours, but not more than 24 hours. After the waiting period, drain the water through every faucet and shower head on the boat. (It’s a good idea to remove any diffusion screens from the faucets at this point, because the gunk that’s likely to come out could cause a clog.) Fill the tank with fresh water only, and drain it again through each outlet. Clean and reinstall the aerators at the faucets. Then fill your tanks with fresh water as you normally would.

If the water has an excessive chlorine taste or odor, mix a solution of one quart white vinegar to five gallons water, pour it into each tank, and allow it to agitate in the tanks for a few days—either by rocking the boat dockside or going for a sail or two. Drain and flush the tanks with potable water again, just as before. If you want to take your tank re-commissioning a step further, consider replacing the soft water-delivery hoses, which tend to absorb bacteria.

Remember, in the U.S. (and most other developed nations), the molds, fungi, and bacteria in onboard waater systems are unpleasant, but these are usually just an aesthetics issue, not a water-purity issue, Hall reminded us. Unless you’re using well-water, the water supply has already been purified."


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## RichH (Jul 10, 2000)

One has be informed or remember that the US has recently and continues to spend zillions of $$$ in its upgrades to prevention of bio-contamination of its municipal water system, especially those systems that rely on 'surface water'. 
Starting in about the late 1980s and early 90s a 'lot' of the US water supply was found to be contaminated with certain 'oocysts' that were resistant to typical chlorine sanitization and maintenance dosages. These chlorine resistant 'microorganisms' were responsible for a LOT of serious illness and even death - do websearch for: cryptosporidium OR giardia OR/AND especially "cryptosporidium+Milwaukee" where it is now estimated by CDC that several HUNDRED died as a result. You can also do the same research w/r to 'giardia'. 
Here's a lite-reading summary of the MIlwaukee, Wisc 'outbreak': 




Most municipal water systems are now additionally 'filtered' (RO and other methods) to prevent such organisms from contaminating the potable supply .... but still not 'all' have completed these efforts. The advice already given to 'pre-filter' your tank water (at the dock before it enters your tank) with a filter 'validated for the retention of oocysts' remains quite valid, especially when traveling through areas where you have no idea of their water quality and the efficacy of their water treatment.

Please strongly consider that what you read 'on the internet' especially by so-called experts etc. is not always factual nor correct.


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## Minnesail (Feb 19, 2013)

Small Town's 'Cryptosporidium Daze' Fails To Attract Visitors


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## PeterJYC (Mar 11, 2011)

So what about us with rubber/non-ridgid tanks without inspection ports? Is there anyway to clean those? Sloshing around by hand while little or no water inside?


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## pdqaltair (Nov 14, 2008)

The same old ANSI 199.2 / US Public Health method should still apply:

-----

Use one of the following methods to determine the amount of common household bleach needed to sanitize the tank: 
A. Multiply “gallons of tank capacity” by .13; the result is the ounces of bleach needed to sanitize the tank. 
B. Multiply “Liters of tank capacity” by 1.0; the result is the milliliters of bleach needed to sanitize the tank. 

2. Mix into solution the proper amount of bleach within a container of water.

3. Pour the solution (water/bleach) into the tank and fill the tank with potable water.

4. Open ALL faucets (Hot & Cold) allowing the water to run until the distinct odor of chlorine is detected.

5. The standard solution must have four (4) hours of contact time to disinfect completely. Doubling the solution concentration allows for contact time of one (1) hour.

6. When the contact time is completed, drain the tank. Refill with potable water and purge the plumbing of all sanitizing solution.

-----

I would definatly pre-filter, since removing solids is going to be a bugger.


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## RichH (Jul 10, 2000)

pdqaltair said:


> The same old ANSI 199.2 / US Public Health method should still apply:
> 
> -----
> 
> ...


Please note that ANSI 199.2 ONLY APPLIES to CLEAN (cleaned) tanks/water systems. 
If the tankage, etc. has a developed 'calcyx' - a large 'slimy coating' indicative of a massive bacteria colony, a 'slime' that you can feel with your hands/fingers on the inside walls, etc. of the tankage, then you will need to do 'repetitive' / repeated shock sanitizations. The reason is that 'disinfectants and sterilants' do not 'penetrate' into or through such 'bacterial slimes', thus killing/stunning only the 'surface layers' of the bio-growth thus leaving the bio-growth sill alive below the 'surface layers'.


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## pdqaltair (Nov 14, 2008)

RichH said:


> Please note that ANSI 199.2 ONLY APPLIES to CLEAN (cleaned) tanks/water systems.
> If the tankage, etc. has a developed 'calcyx' - a large 'slimy coating' indicative of a massive bacteria colony, a 'slime' that you can feel with your hands/fingers on the inside walls, etc. of the tankage, then you will need to do 'repetitive' / repeated shock sanitizations. The reason is that 'disinfectants and sterilants' do not 'penetrate' into or through such 'bacterial slimes', thus killing/stunning only the 'surface layers' of the bio-growth thus leaving the bio-growth sill alive below the 'surface layers'.


Rich is 100% correct, and that is the pickle; there is no easy substitue for scrubbing. You can't sanitize dirt.

And it should have been ANSI 119.2. I typed too fast.


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## gbgreen59 (Aug 20, 2013)

Can the water with bleach in it be considered "brown" water and put back into the water in which the boat is sitting? Or must the water with bleach be put in containers and emptied elsewhere?


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## pdqaltair (Nov 14, 2008)

Good question. From a legal perspective, no one will want to say "OK."

The practical side. 

* The bleach should not have contaced or reacted with anything toxic. I certainly hope not. It was an unscented product containing only water, hydroxide, and hypochlorite.
* If you sanitized a 40 gallon freshwater tank, you used 1/2 cup of bleach. It would not be unheard of for someone to use that amount cleaning mildew from the exterior of a boat. Perhaps 30% of the bleach has already been spent doing its work, so perhaps 1/3 cup.
* When the bleach decomposes in the water the result with be saltwater. No problem there. However, there will be some acute toxicity to any organisms very near the discharge for a short time. Ther ewill be traces of disinfection by products.

Jugging 40 gallons to the nearest toilet sounds impractical. Don't put it in the holding tank; you don't want that sanitized and some chloramine may be released (urea + chlorine).

If I felt really bad about it--I don't--I might consider nuetralizing the bulk of it in the tank by adding 1 cup of hydrogen peroxide (will oxidize bleach to NaCl and O2) and waiting an hour for mixing (Chlorox confirms this advice). But I'm also not worried about it.


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## RichH (Jul 10, 2000)

Here's a definitive standard for sanitizing industrial 'purity' water systems including schedules of 'shock sanitizing' and the soak times of the tankage. At the time this paper was written it was considered 'state of the art' and was derived from FDA/NSF/AWWA standards - a compilation. 
Please note that this is for SHOCK sanitizing which is 10 times the 'potency' than for maintenance dosages. http://www.edstrom.com/file.aspx?DocumentId=71

The usual 'maintenance' chlorine dosage for municipal water systems is typically 1ppm (4oz. 'clorox' per 100 gallons of water) and a 'shock sanitizing' dosage of ~10ppm or about *40oz. of 'clorox' per 100 gallons*. 
You'll note that in 'bio-fouled' (slimed) systems, even with successive/repeated chlorine based 'shock sanitizations' that the 'kill' is only 90%; and, thats why a 'maintenance dosage' is always needed.

BTW/Other 
- the hydrogen peroxide listed in this referenced document is 'full strength' peroxide and is VERY dangerous to handle and NOT available to 'consumers'. 3% 'drugstore' hydrogen peroxide simply does not have the 'potency' to affect any reasonable measure of 'sanitization', even if you totally filled your water tank with it.
- as regarding 'brown water', housewives have been 'dumping' laundry bleach water for the past 100+ years. The 'half-life' of SodiumHypoChlorite in water in an 'open' sewerage system is very short.


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## SVAuspicious (Oct 31, 2006)

gbgreen59 said:


> Can the water with bleach in it be considered "brown" water and put back into the water in which the boat is sitting? Or must the water with bleach be put in containers and emptied elsewhere?


I think the terminology you are looking for is 'gray water.' I believe that at reasonable concentration you can let it go overboard.


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## gbgreen59 (Aug 20, 2013)

SVAuspicious said:


> I think the terminology you are looking for is 'gray water.'


 Oh boy, a novice revealed again.  I probably won't get it wrong in the future though...thanks for the clarification.


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