# holding tank vent fitting



## Fitz87 (Oct 27, 2009)

I have tried to read everything I can find here on the subject so if there are other posts you think would be useful, please let me know. 

My holding tank has just 1 vent, is small (maybe 5/8") and it goes to a fitting on the deck that looks like a water fill or something. I hear it hissing whenever I flush the head. I'll be out there Wednesday and may be able to get a picture. But the bottom line is that I need a new (and likely 2) vent fittings.

My question is this - what to use as a vent fitting. I have read a standard 1" through-hull just below the rail. 

1. This seems big, and 2. is there no "holding tank vent fitting?"

Please forgive my ignorance, but drilling holes in my boat makes me queazy!

I have a Tartan 3000, '83 and sail mostly in protected water with trips out in the ocean as often as I can (a few times a year).

Thanks,
Fitz


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## sawingknots (Feb 24, 2005)

i would think your small vent is adequate,gases don't take much passage.my motto if it in't broke don't fix it


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## sailingdog (Mar 19, 2006)

Upgrade it to a 1" hose and use a 1" through-hull. If you want to cover it, use a stainless steel clamshell. This is the recommendation by Peggie Hall, who is the last word on marine head systems.


BTW, I would recommend taking care of this sooner, rather than later, since the hissing indicates your vent line is at least partially clogged... and if it clogs completely, bad things will happen.


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## CalebD (Jan 11, 2008)

Fitz87 said:


> <snip>
> 
> My holding tank has just 1 vent, is small (maybe 5/8") and it goes to a fitting on the deck that looks like a water fill or something. I hear it hissing whenever I flush the head. I'll be out there Wednesday and may be able to get a picture. But the bottom line is that I need a new (and likely 2) vent fittings.
> 
> ...


If your holding tank vent is on deck and not over the side on the freeboard of your boat you may likely be able to smell the vent in the cockpit. I have seen some set ups where the holding tank vent is routed to a lifeline stantion, but even with this set up you could smell the vent in the cockpit when the head was used. The vent should not look like a 'water fill' which would more likely be a pump out fitting which is usually mounted on the deck and should not be hissing when the head is pumped. The vent is there to allow the air to escape as liquids are pumped in. Look overboard for the actual vent hole as it is probably clogged. Been there, done that, does not smell good.

I highly recommend a second vent for your tank as the more air your tank gets the less stinky it will be. Peggie Hall's book is a great resource for MSDs or heads: "Get rid of boat odors" or something to that effect.
Amazon.com: Get Rid of Boat Odors: A Boat Owners Guide to Marine Sanitation Systems and Other Sources of Aggravation and Odor (9781892399151): Peggie Hall: Books


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## GaryHLucas (Mar 24, 2008)

I've bought a new ridgid holding tank annd I'm trying something a little different. I have two vent holes in my new tank, port and starboard. I'm installing two vent hoses that will come together at a Y fitting just below the deck fitting. No matter which way the boat heels one vent will be above the water level. I figure that when the boat rocks air will be pumped in and out of the tank, helping to keep it aerated and reducing the smell. I work in the wastewater industry. I have 10,000 gallon sewage tanks with 1% bio solids in them and there is NO smell as long as they are kept aerated! We'll see!

Gary H. Lucas


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## sailingdog (Mar 19, 2006)

Gary-

I think you're going to run into a problem. This type of setup pretty much guarantees that the vents will clog when the boat is heeled. The vents should be as close to centerline so that they're less likely to be filled with the tank's contents.

Also, using the Y fitting means that most of the air will just vent between the two through-hulls...



GaryHLucas said:


> I've bought a new ridgid holding tank annd I'm trying something a little different. I have two vent holes in my new tank, port and starboard. I'm installing two vent hoses that will come together at a Y fitting just below the deck fitting. No matter which way the boat heels one vent will be above the water level. I figure that when the boat rocks air will be pumped in and out of the tank, helping to keep it aerated and reducing the smell. I work in the wastewater industry. I have 10,000 gallon sewage tanks with 1% bio solids in them and there is NO smell as long as they are kept aerated! We'll see!
> 
> Gary H. Lucas


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## Fitz87 (Oct 27, 2009)

Thanks for all the input. 

I am going to the boat today and will see what options I have. It definitely stinks right now and any change will be for the better! I think I'll try to get the existing line run to a decent outlet on the topsides and then put in a 1" to a through hull on the other side (sort of a compromise I guess).

I like the idea of 2 vents but I am pretty sure my tank does not have a second vent outlet. Any tips on how to put a new outlet in the top of a holding tank?

I'm also going to pump the tank out today, change to flushing with fresh water, and pick up a bottle of KO.


Thanks again,
Fitz


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## GaryHLucas (Mar 24, 2008)

sailingdog said:


> Gary-
> 
> I think you're going to run into a problem. This type of setup pretty much guarantees that the vents will clog when the boat is heeled. The vents should be as close to centerline so that they're less likely to be filled with the tank's contents.
> 
> Also, using the Y fitting means that most of the air will just vent between the two through-hulls...


Dog,
Unless your tank remains empty, you sail a catamaran, and only when there is no wind, I'd say it is safe to assume that waste water WILL be going up the vent hose on EVERY holding tank! So I figure two vents that are each 4 times larger than the previous vent lines is going to have a LOT less chance of clogging.

I've thought about the issue you mention with the Y fitting. Everybody recommends a large tank vent, and NOBODY makes larger vent fitting for the deck! Go figure!

Gary H. Lucas


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## Fitz87 (Oct 27, 2009)

So- not only was the vent fitting basically plugged, there was a low spot in the tube and it was filled with wastewater! I got some new tubing and ran it to a fitting just below the rail and also secured the line to keep a constant grade draining back into the tank.

So far what I have found on puting a new vent port in the holding tank shows that you really have to put in an access hatch so that you can get to the inside of the tank and then use a plastic/marelon through-hull fitting for the vent. Does this sound right? Does the access hatch cause any odor to leak out?

Thanks
Fitz


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## jbondy (Mar 28, 2001)

Fitz87 said:


> Does the access hatch cause any odor to leak out?


In my experience, yes. I've been following this thread for two reasons, and this is one of them. I installed a new tank a few years back. The new one came with threaded holes for various openings, including one 5/8" vent opening. I've wanted to expand it to two 1" vents and don't want to install the access hatch. I was hoping to learn some trick for installing the vent hose without one.

The second was to understand the issues associated with installing a second vent to allow cross ventilation. Our holding tank is under the v-berth on the starboard side in the open part of the V. I don't think I can have a clean run to a port vent with no low spots, so it may not be feasible.


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## sailingdog (Mar 19, 2006)

If the vent hoses are piped into the tank on the outboard edges, you pretty much guarantee they'll be sitting full of sludge any time the boat is under sail on one tack and the tank is fairly full. If the vent lines are routed into the tank along the centerline of the boat, they're going to be far less likely to be submersed unless the tank is completely full.

As for the y-fitting, I just realized you're connecting a SINGLE deck through-hull to two vent fittings on the tank... that will probably work fairly well. Peggie Hall suggests using a plain marelon through-hull for the topside vent fitting, rather than a vent fitting like normally seen, since they don't make a 1" ID hose vent fitting. I'd point out the main reason for the screen on the vent fitting is to prevent insects from getting in... and with a 1" diameter hose, that's a much lower concern, since it would take a lot of spider web or wasp nest to clog it.

Peggie Hall also recommends flushing the vent line every time you pump out the tank...


GaryHLucas said:


> Dog,
> Unless your tank remains empty, you sail a catamaran, and only when there is no wind, I'd say it is safe to assume that waste water WILL be going up the vent hose on EVERY holding tank! So I figure two vents that are each 4 times larger than the previous vent lines is going to have a LOT less chance of clogging.
> 
> I've thought about the issue you mention with the Y fitting. Everybody recommends a large tank vent, and NOBODY makes larger vent fitting for the deck! Go figure!
> ...


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## knothead (Apr 9, 2003)

Every time I read one of these thread, I appreciate my bucket even more.


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## Fitz87 (Oct 27, 2009)

what a surprise - the boat no longer stinks! Sure, it still smells like an old dirty bilge (next project) but it no longer smells like someone's been crapping in my V berth. KO, fresh water, a working vent... I may just go with it for now and see what happens. I can always put in a second vent later.

I have learned alot from this forum and the helpful people here- 

Thanks


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