# How does a sink drain work?



## jarcher (Jul 29, 2008)

On my boat, there is a thru hull below the water line. The drain from the sink in the gally goes directly to it. So, that means the sink never actually drains. As near as I can tell, that thru hull is useless.

I was thinking I could drain the sink into a small holding tank with a float triggered bilge pump in it. 

Or, is there any reason not to just drain it into the bilge and let the bilge pump take care of it? I hardly ever actually use the sink anyhow. We mostly store beer in it


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## Faster (Sep 13, 2005)

Yeah, but if a beer can leaks you'd have beer in the bilge..

The water level in your sink drain will, of course, be at the waterline level. If the bottom of your sink is close to waterline, then the sink will barely drain, ie water in the drain line will always be there. - If your sink actually won't drain at all, then it's either too low in the boat (or too deep for that location) or the drain line is plugged somewhere. 

Also if the sink is a ways off centerline then you're probably going to get water back into the sink when heeled towards that side. On many boats one of the pre-sailing routines is to close such sink through hulls (galley and/or head) to avoid a wet surprise the first time you tack.

Adding a tank/pump sounds unnecessarily complicated.


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## kaluvic (Jan 14, 2009)

I wouldn’t drain it into the bilge...its just so nasty...imagine everything that’s left on your plate when you finish eating, all over your bilge...the oil is probably the worst.
Is it possible to plumb the sink to a holding tank that is above the waterline so you can drain it over the side via gravity.
If you can do this its so sweet...you will need to put a P or bottle trap between the sink and the tank....you'll also need to vent the tank.


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## erps (Aug 2, 2006)

Your sink at home always has water trapped in the drain too, in the P-trap. I would leave the sink drain alone and sand some teak instead.


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## jarcher (Jul 29, 2008)

Faster said:


> Also if the sink is a ways off centerline then you're probably going to get water back into the sink when heeled towards that side. On many boats one of the pre-sailing routines is to close such sink through hulls (galley and/or head) to avoid a wet surprise the first time you tack.
> 
> Adding a tank/pump sounds unnecessarily complicated.


The botom of the sink is probably not far above the waterline at all, and yes, when I heel the sink can fill. I just closed the thru hull and have not opened it, since I rarely use the sink.

Since the bottom of the sink is so low I don't see how a gravite fed extra tank would work, but I am probably missing something.

I suppose I could also lower the thru hull? If I do that woudl the sink actually drain when the boat is sitting still?


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## klem (Oct 16, 2009)

Lowering the thru hull will not make any difference. What matters is the height of the sea water relative to the height of the bottom of your sink. The two of these should equalize rather quickly. If they are not, you probably have an obstruction in the drain somewhere. I make a habit of using draino from time to time in sinks to clear them out. I suspect that if you were to close the seacock and take the hose off, it would be pretty plugged up with stuff. I have even had to snake drains from time to time.

I don't recommend using a gray water tank if you can help it for the same reason that the line is giving you problems. Lots of grease and coffee grounds tend to go down sinks and are very hard for small pumps to deal with and they slowly fill up the tank. If you use a gray water tank, you will need to open up the top from time to time and manually clean it out. On the commercial boats that I worked on, it was common practice to fully clean all black and gray water tanks twice a season and many people preferred to do the black over the gray. There is nothing like having a pumpout clog and then needing to unclog it while the tank is full.


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## xact (Apr 21, 2006)

You pour draino into the water?
great makes me want to be swimming around your boat


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## jarcher (Jul 29, 2008)

Okay Klem, thanks, I see what you all mean now. I'll check for clogs. That should be easy enough, now that I'm on the hard I'll just pour some water into the sink and see how quick it drains. Replacing a few feet of tubing should be easy enough as well.


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## sailingdog (Mar 19, 2006)

I'd recommend you leave it alone. A grey water tank will become a maintenance nightmare in short order.


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## Sabreman (Sep 23, 2006)

Could also be marine growth in the through hull. We routinely clear them when we haul for the winter. There always barnacles hiding up in the hole. A quick, easy way to clear a clog is to blast it with a jet from a hose. Of course, you could end up with a face full of water. We also use a length of clothes hanger to open clogs (the drain hose should have few if any bends).


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## kaluvic (Jan 14, 2009)

The rules for discharge are changing fast....some places are not allowing even grey water discharge.
Everything on my boat goes into a tank first.
Unfortunately for us lovers of KISS ...its going to be the new reality for lots of places.
Good luck.


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## klem (Oct 16, 2009)

kaluvic said:


> The rules for discharge are changing fast....some places are not allowing even grey water discharge.
> Everything on my boat goes into a tank first.
> Unfortunately for us lovers of KISS ...its going to be the new reality for lots of places.
> Good luck.


That is a good point. You may be in an area that doesn't allow grey water discharge so even if you fix the clog, you might still be illegal. Luckily, I have not run into that yet but it sure adds hassle. Kind of depends how much of a chance you are willing to take.


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## kaluvic (Jan 14, 2009)

I'm going to Turkey.....Did you see Midnight Express?


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## RXBOT (Sep 7, 2007)

Why not just get a 2-5 gallon container ( bleach bottle,commercial oil pail) adapt drain to pour spout of container. Just dump onshore or offshore when needed. Glass in thru hull opening 4 peace of mind.


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## jarcher (Jul 29, 2008)

RXBOT said:


> Why not just get a 2-5 gallon container ( bleach bottle,commercial oil pail) adapt drain to pour spout of container. Just dump onshore or offshore when needed. Glass in thru hull opening 4 peace of mind.


This sounds like a good option actually, provided I can secure the bottle.

Removing the thru hull and glassing over it was the plan, more because I was concerned about performance. Not that it makes a huge difference. I have a few others that I don't need, like the one the toilet pumps out into the water through. That one will never be used.

But if I can make it work by clearing a clog then I'll probably just do that.


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## kaluvic (Jan 14, 2009)

Before you start closing them permanently, think re-sale value.
I like the jug under the sink idea as well.


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## jarcher (Jul 29, 2008)

kaluvic said:


> Before you start closing them permanently, think re-sale value.


Yeah, its a 32 year old boat and I have way, way too much money sunk into it to ever sell. Besides, adding a thru hull is as easy as drilling a hole.


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## DwayneSpeer (Oct 12, 2003)

erps said:


> Your sink at home always has water trapped in the drain too, in the P-trap. I would leave the sink drain alone and sand some teak instead.


Here Here. It's a common situation in almost all boats. Leave it alone.


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## captain jack (May 5, 2013)

RXBOT said:


> Why not just get a 2-5 gallon container ( bleach bottle,commercial oil pail) adapt drain to pour spout of container. Just dump onshore or offshore when needed. Glass in thru hull opening 4 peace of mind.


so, that's not actually a crazy idea? i have been toying with that idea for some time. i want to glass in all of my through hulls, for peace of mind, and the galley drain is the only one that is actually in use. i thought about a grey water tank pumping out to a drain at the transom but the idea of clogs ruled that out; plus it would be another drain on the batterys.

so, i was thinking of a 'bucket' under the drain that i could just dump overboard after use. less holes in the hull is better and no holes is best.


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## knuterikt (Aug 7, 2006)

captain jack said:


> so, that's not actually a crazy idea? i have been toying with that idea for some time. i want to glass in all of my through hulls, for peace of mind, and the galley drain is the only one that is actually in use. i thought about a grey water tank pumping out to a drain at the transom but the idea of clogs ruled that out; plus it would be another drain on the batterys.
> 
> so, i was thinking of a 'bucket' under the drain that i could just dump overboard after use. less holes in the hull is better and no holes is best.


Thanks for reviving a 5 years old thread
RXBOT did his last post 3 years ago..

How often have a *well *maintained boat sunk because of a through hull?


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## capt jgwinks (Sep 24, 2013)

My boat has a nice double galley sink with 1 1/2" drains, just like one in a shore side kitchen. That feature alone was enough to convince the Admiral. Problem is the through hull is 3/4" so the point where the line chokes down clogs up a lot. We have to be real careful of what goes in there. It was originally plumbed with a tee between the sinks, then the reducer, then the hose to the through hull. I redid it with the tee now directly under one of the drains so now I can run a coat hanger in there to clear the clogs.


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## captain jack (May 5, 2013)

knuterikt said:


> Thanks for reviving a 5 years old thread
> RXBOT did his last post 3 years ago..
> 
> How often have a *well *maintained boat sunk because of a through hull?


well, from what i have read information about through hulls, a lot of boats sink because of them. even on a well maintained boat, things can start to have issues and you might not find out until there is a big problem.

Murphy uses my life as a test bed for his laws. if a disaster can possibly, in any way, happen, it's going to happen to me. stuff that seems totally fine under inspection, today, will blow up on me tomorrow. so, i have learned to minimize the chances of things going wrong. simplicity is better than complexity. no power windows or power locks; i have hand winders and manual locks on my vehicles. less to go wrong.

under most conditions, a diligently maintained seacock might be bullet proof. but, it only takes one time for that not to be the case for your boat to sink.

my boat doesn't have proper seacocks. it's got gate valves threaded onto the through hulls. when i haul it, this spring, that will be right at the top of my fix it list. there are a number of unnecessary through hulls i am going to get rid of. no need to have them if i don't need them or use them. it's just more to check out and more to have a problem. the only through hull that i will be using is the galley sink drain. if i could get rid of that, too, i'd have a boat with no holes in the hull below the waterline.

let's face it, that what through hulls are: holes in your boat.

if i can have no holes in my boat and still wash dishes and wash my face and hands, why not?

i had been considering a shower sump for the galley drain. the problem is where to route the discharge. the best would be out through the transom. however. my galley is amidships. that would be a long run. then, if you take it out far enough above the waterline to not be a risk when heeled, you get a mess down the sides of your boat.

i'm not exactly lazy so dumping a bucket overboard after i do the dishes doesn't seem like that big a price to pay for one less hole in the boat.


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## Capt Len (Oct 9, 2011)

Good thruhulls are the minimal risk. Good hoses, clamps and direct routing are important. Biggest risk is the connection to the sink. Anything can happen under the counter and if the hose falls over when the brass bibs fail and floods ??? A short handle toilet plunger and a rag stuck in the second sink can be a good friend until you install a matching' hole in the boat'


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## captain jack (May 5, 2013)

Capt Len said:


> Good thruhulls are the minimal risk. Good hoses, clamps and direct routing are important. Biggest risk is the connection to the sink. Anything can happen under the counter and if the hose falls over when the brass bibs fail and floods ??? A short handle toilet plunger and a rag stuck in the second sink can be a good friend until you install a matching' hole in the boat'


a short handled toilet plunger and a rag?


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## Capt Len (Oct 9, 2011)

Just requires a thorough under standing of suck and blow. If you don't plug one sink ,no pressure is applied to the goop blocking the thruhul. Simple directions,,,1Partialy fill plugged sink,2 ,Plug one sink with rag ,hold in place. 3 apply plunger to other sink with gusto. Anyone not able to follow this,, should practice by bleeding their engine of air.


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## captain jack (May 5, 2013)

Capt Len said:


> Just requires a thorough under standing of suck and blow. If you don't plug one sink ,no pressure is applied to the goop blocking the thruhul. Simple directions,,,1Partialy fill plugged sink,2 ,Plug one sink with rag ,hold in place. 3 apply plunger to other sink with gusto. Anyone not able to follow this,, should practice by bleeding their engine of air.


oh. got you.


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## hellsop (Jun 3, 2014)

knuterikt said:


> How often have a *well *maintained boat sunk because of a through hull?


*grin* If people always remembered to close seacocks, doing wouldn't be on every good checklist about four times.


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## miatapaul (Dec 15, 2006)

captain jack said:


> so, that's not actually a crazy idea? i have been toying with that idea for some time. i want to glass in all of my through hulls, for peace of mind, and the galley drain is the only one that is actually in use. i thought about a grey water tank pumping out to a drain at the transom but the idea of clogs ruled that out; plus it would be another drain on the batterys.
> 
> so, i was thinking of a 'bucket' under the drain that i could just dump overboard after use. less holes in the hull is better and no holes is best.


Seems a shower sump would be a good solution, and feed it to a through hull above the waterline.

Rule Shower Drain Pump System

Even looks like the pump is removable so you could likely use it in an emergency as a third backup pump.


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## captain jack (May 5, 2013)

miatapaul said:


> Seems a shower sump would be a good solution, and feed it to a through hull above the waterline.
> 
> Rule Shower Drain Pump System
> 
> Even looks like the pump is removable so you could likely use it in an emergency as a third backup pump.


that's the one i was considering.


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## sulli (Mar 9, 2013)

Pearson 30 has a fiberglass tube straight through the bottom no seacock, I can look down the drain hole and see stones since the snow melted.
It has been there since 1976 but I am thinking it would be good to add a seacock.


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## seaner97 (May 15, 2011)

sulli said:


> Pearson 30 has a fiberglass tube straight through the bottom no seacock, I can look down the drain hole and see stones since the snow melted.
> It has been there since 1976 but I am thinking it would be good to add a seacock.


Common on the Pearsons. Many (all?) of them have a glassed in tube that goes up above the waterline to remove the possibility of the hose clamps and hose failure. Have dipped the rails on my P35 and not gotten water in. I think you'd need a good knockdown before you'd have an issue with that design. And if you've got enough time for water to be coming in that direction, you've probably got bigger problems.


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## captain jack (May 5, 2013)

sulli said:


> Pearson 30 has a fiberglass tube straight through the bottom no seacock, I can look down the drain hole and see stones since the snow melted.
> It has been there since 1976 but I am thinking it would be good to add a seacock.


wow. yeah. i'd agree.


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## bblument (Oct 22, 2012)

seaner97 said:


> Common on the Pearsons. Many (all?) of them have a glassed in tube that goes up above the waterline to remove the possibility of the hose clamps and hose failure. Have dipped the rails on my P35 and not gotten water in. I think you'd need a good knockdown before you'd have an issue with that design. And if you've got enough time for water to be coming in that direction, you've probably got bigger problems.


Thanks for posting that. My Pearson 26 is like that, too; the two cockpit scuppers/drains are connected via hoses to two glassed-in tube risers and through hulls directly below them, and my sink drain is connected to one of those hoses via a T fitting. Everything works fine and, as previous posters have said, the tops of those tubes are above the waterline so even if a hose failed I'd be OK, but I too get a little freaked out wondering what would happen should one of those riser tubes develop a crack or break.

Someone, tell me that those tubes never crack or break. I could use a little reassurance!

Thanks..

Barry


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## seaner97 (May 15, 2011)

bblument said:


> Thanks for posting that. My Pearson 26 is like that, too; the two cockpit scuppers/drains are connected via hoses to two glassed-in tube risers and through hulls directly below them, and my sink drain is connected to one of those hoses via a T fitting. Everything works fine and, as previous posters have said, the tops of those tubes are above the waterline so even if a hose failed I'd be OK, but I too get a little freaked out wondering what would happen should one of those riser tubes develop a crack or break.
> 
> Someone, tell me that those tubes never crack or break. I could use a little reassurance!
> 
> ...


If you're really worried, an extra layer of glass wrapped around it every 50 years should do the trick.


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## CarbonSink62 (Sep 29, 2011)

bblument said:


> Someone, tell me that those tubes never crack or break. I could use a little reassurance!


I have never in my life been on a Pearson 26 that had the drain tubes crack or leak in any way.


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## ODAY 28 Sailor (Mar 28, 2016)

I have an Oday 28 that has a through hull for the galley sink. Why when its open does water not run into sink? Will it just rise in pipe to the water line? How does the sink drain then, wouldnt the water just sit in the sink and eventually overflow? Why didnt they just make the drain above the waterline like the head sink?Very confused...thanks


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## Faster (Sep 13, 2005)

ODAY 28 Sailor said:


> I have an Oday 28 that has a through hull for the galley sink. Why when its open does water not run into sink? Will it just rise in pipe to the water line? How does the sink drain then, wouldnt the water just sit in the sink and eventually overflow? Why didnt they just make the drain above the waterline like the head sink?Very confused...thanks


Water in the hose between your sink and the throughull will equalize to be level with the water outside the boat... so yes, at the waterline. If the bottom of your sink was actually below the waterline then your sink would not drain any lower than the waterline.

Any open through-hull attached hose will have water in it up to the waterline. On some boats it's a problem if the sink is outboard, you can 'heel' the sink below the waterline and basically backflow and flood your boat. Closing that particular sink drain through-hull should be on your 'pre-sail checklist'.


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## ODAY 28 Sailor (Mar 28, 2016)

The through hull is located in the middle of the hull so no issue there, just wonder why it is even below water line, why not drain above water line?


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## JimsCAL (May 23, 2007)

ODAY 28 Sailor said:


> The through hull is located in the middle of the hull so no issue there, just wonder why it is even below water line, why not drain above water line?


Bottom line is that it makes no difference. The water drains either way. Even if the drain is above the water line at the dock, it will probably be below on one tack or the other. Sink still drains. The location is driven more by the location of the sink and how best to run the drain hose.


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## albrazzi (Oct 15, 2014)

We prefer to call it a Basin, don't like to use the "S" word on board.


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## Faster (Sep 13, 2005)

Personally I don't like to see someone's sink being dumped through a visible, above the water fitting. I know it makes no difference, really, but releasing that grey water a foot or so below the waterline disperses it better, and is less visible.


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