Non-return valve on sink drain

rptb1

rptb1

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tammynorie.wordpress.com
Tammy Norie https://tammynorie.wordpress.com/ has a cunning fold-away sink that drains through 3/4" flexible pipe to a seacock on the starboard side. The sink isn't much above the waterline, and if I forget to close the seacock it spills into the starboard under-seat lockers and then to the bilge. None of this is critical -- the starboard locker contains the flexible water tank, and the amount of water ingress is small -- but it makes the boat wet.

I'm wondering if it would be sensible to fit some sort of non-return valve in the sink drain pipe.

The idea is just to stop or reduce the amount of water that backs up if I forget the seacock. It doesn't matter much if it fails to work or is imperfect. It'll just save me on those occasions when I up anchor and start sailing before I remember about it.

A valid answer is "just don't forget your seacocks idiot".

However, any advice, experience, or pointers to relevant valves would be appreciated.
 
Is this a galley sink or a heads washbasin?

I'm thinking of fitting a valve in my own heads basin for the same reason, but I wouldn't put one in the galley sink drain as it might clog up with food waste etc.

Pete
 
It's the one-and-only sink, but food waste goes over the side and lumpy washing up happens in a bucket, so I'm not too worried about clogs. However, it'd probably be a good idea to fit the valve at the sink end so that it's feasible to get at it above the waterline.
 
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If the non-return valve doesn't have much head of water to force it open it will likely stick together with cooking fats etc.
You can always have a plunger on hand.
 
I have the same issue (Rival 32, galley sink)
I note that the head hand-basin is not a problem. It has the drain and seacock on the port side, whereas the basin is to stbd.
In the galley sink however, the sink is same side (port) as the seacock. When the toe-rail gets wet (slow to put a reef in!), then water backs up. The rubber sink plug isn't enough.
The water fills the sink, then overflows down into the pots cupboard, and so to the bilge.
Bilge capacity is huge, but I remember the first time I saw this from the cockpit. Heeled over for a while, shipped what might have been several buckets of water, then came upright, to see a mini-tidal wave rushing out from under the stove and pot locker. "We're sinking, where's the wooden hull plugs?".
A non-return valve might help for the times I also forget to close the seacock when setting off.
 
On my Twister the top of galley sink is not much above the waterline and the bottom is probably below it. There's no problem with back-flooding because the sink is emptied with an old brass Whale pump that has a non-return valve built in.
 
prv said:
Is this a galley sink ......... I wouldn't put one in the galley sink drain as it might clog up with food waste etc. ....
Click to expand...

MM5AHO said:
I have the same issue ...... In the galley sink however, the sink is same side (port) ..... The water fills the sink, then overflows down into the pots cupboard, and so to the bilge. .... A non-return valve might help for the times I also forget to close the seacock when setting off.
Click to expand...

My own yacht was fitted with an NRV in the galley sink but that failed to fix the issue as the NRV simply became clogged up with bits of stuff and the water still back flowed when healed over. It was quite an industrial affair, about 1.5" ID with a cup device that slid up and down a small shaft as opposed to a flapper valve. A possible solution is probably a manual pump that pumps out the sink contents which has built in flapper style NRVs. In my case I have decided to close the seacock as a solution.

My galley became very difficult to drain after a few years, despite boiling water, cleaning products and plunger work (the plunger came with the boat) to try and flush out the crud but yet it still managed to back flow. Eventually when I removed the fitting the cup device was simply very stiff on the shaft. My advise would be to keep it simple and close the sea cock if that works. If you have Blakes style (plug type) seacocks you will have to grind the cones in to give a good finish otherwise they will pass quite easily when in the closed position.
 
rptb1 said:
It's the one-and-only sink, but food waste goes over the side and lumpy washing up happens in a bucket, so I'm not too worried about clogs. However, it'd probably be a good idea to fit the valve at the sink end so that it's feasible to get at it above the waterline.
Click to expand...

In that case, remove the seacock completely and fill the hole... just drain the sink into a bucket if you want to use it, and then chuck contents over side... one less hole in the boat = :encouragement:
 
Fantasie 19 said:
In that case, remove the seacock completely and fill the hole... just drain the sink into a bucket if you want to use it, and then chuck contents over side... one less hole in the boat = :encouragement:
Click to expand...

If I keep Tammy long term it's likely that all holes below the waterline will go, with the possible exception of the cockpit drains, so I'm totally with you.
 
Eynhallow has 2 heads sinks and galley sink all on the starboard side. None of them have much head.

The forwards heads works OK when the sink is full, but leaves a couple of cm of water in the bottom of the sink, which is slow to drain. I guess that here isn't enough head to drain the last bit of water out against the weight of the NRV flap.

We've never had a problem with the galley drain, except that it's slow sometimes and needs a workover with a plunger.

The aft heads NRV leaks when the boat is well healed over, so I shut the seacock. No amount of working with a plunger seems to make any difference, so I'll have to take it apart this winter to see if there something stuck in it.

So my conclusion is, NRV are OK, but don't completely solve the problem. Turning the stop cock off is the real answer, but not very convenient when you have guests and family on board.
 
I have a different mechanism working on Mojo. The water tank is under the dinette seat on the port side and the sink is on the starboard side. Unless I close the cock on the supply line when sailing hard pressed, the water flows up into the sink and overflows onto the cabin sole. Even if the drain cock is open, enough water accumukates in the sink to slop around all over the place!

As regards the drain, I recall the PBO sketchbook suggesting that the drain should be extended up as high as possible from a tee beneath the sink to relive the pressure in the hose and improve drainage. It also means that with the plug inserted, any flow should go up the pipe extension rather than into the sink.

Rob.
 
I fitted a pop up sink waste on the wash hand basins. You just push the thing down befoe you sail. You still need to remember to do it but a lot easier than crawling under the sink in the cupboard to find the seacock each time you want to use the sink.
 
Put a small handpump twixt basin and seacock and pump the basin dry.
Seawater won't flow backwards unless the pump fails - not highly likely.
 
with this situation I would run waste into small holding tank even a very large ice cream tub and fit a cheapy bilge pump into it and run bilge pump waste out high and no more probs you could even run other things into it as well then no more holes or seacocks to shut off

you can get puprpose made holding tanks for the above but ice cream tub will work quickly and for you to test your happy with it first
 
thegasmannick said:
you can get puprpose made holding tanks for the above but ice cream tub will work quickly and for you to test your happy with it first
Click to expand...

Tammy Norie is a small boat that I frequently sail through big waves. A doubt an ice cream tub would stay put and I'm certain that water wouldn't stay inside it very long! However, the idea of a pump out tank or even just a pump is good (thanks oldvarnish). I've been wondering about a backup pump that I can operate from inside the cabin. You can see me admiring Yacht Auriga's backup pump (with roving hose) here https://www.youtube.com/watch?feature=player_detailpage&v=kkV_w4okp2Q#t=193

So perhaps this is an opportunity to combine a couple of good ideas.
 
Apologies! I did see your post too and should've looked you up for a mention. Please keep bothering.

And thanks to everyone who contributes their ideas and experience. This is a truly great place.
 
I nearly got in first with the pump suggestion, but work intervened and I just hit "Post" on what I had :p

We had a pump on Kindred Spirit's singular sink, which was about level with the waterline (top above the line, bottom below). The original one was a girt ugly thing that stuck out and jabbed you in the leg, so I replaced it with a Whale Smartbail. This is a flush-fitting pump that looks much more acceptable in a living space.

Pete
 
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