why does my head sink drain have a one way valve

[MooGroc]

My shower sump is plumbed into the head sink drain and
below that in the hose leading to the seacock is a one way valve.

The through hull is just at the waterline.

I don't like the idea of having a shower drain and a one way
valve between the sink drain and the seacock. I also don't like
the sound of the ball moving up every time a wave hits the side
of the boat. Then again, we don't use the sink or shower much
so it's easy to keep the seacock closed almost all the time.

Any ideas why the valve is there?

[Calif.Ted]

Perhaps a problem with seawater entering to the sump or sink when heeled on that side ?

[Typhoon]

Originally Posted by Calif.Ted

Perhaps a problem with seawater entering to the sump or sink when heeled on that side ?

Thats a good reason, as well , shower sumps alway smell bad when they are pumping , you don't want that smell entering your galley . Stinky Stinky

Regards John.

[Stu Jackson]

Do you have a shower sump pump?

Have you considered asking Morris?

[MooGroc]

Yes, the shower has a sump pump that is manually operated
and almost never used. I hadn't considered calling Morris, I
guess I could.

I like the OP's theory that it could be to avoid problems when
heeling. Still, I think I'd have to be heeled VERY far over before
water would enter the sink...

[Privilege]

All of my above-waterline discharge outlets have one-way valves just inside the hull. They are there so that if in rough seas, water hitting the side of the hull doesn't squirt water inside the boat. I have the Bosworth check valves which have a rubber flap - so no noise.

[svHyLyte]

With a sink discharge at the waterline, remove the valve and then come down on a sea very hard and the explanation for the valve will be all over the overhead. Do the same with the shower drain, and happen to be standing above it in the same circumstances would be, ah... "enlightening"...

[thinwater]

The OP has me confused.

* Why does the check valve bother him, other than noise? (A different type would solve that.) I can think of several reasons (clogging, freezing), but he needs to say. However, what ever the problem is, it applies equally to the sump pump valves, so it's most likely a non-concern.

* The shower floor is below the waterline. Obviously the sump pump has check valves in it too, but I'm guessing when waves slap they can be over come (they can on my boat--even with a check valve and the valves in the pump, the shower pan will fill after a few hours of hard windward work.

* He says he seldom uses the shower sump pump. I assume that means the shower is seldom used. Kind of irrelevant; it needs to work.

He can take the valve off if he is curious. My bet is that in heavy windward work, the shower will slowly fill. A small high loop is not enough when waves slap hard.

[MooGroc]

I've attached a picture of the hose. What I don't like about it is having so many
clamps and complexity. Seems safer to have a straight run to the sink drain.

But I suspect that's the price to pay for having the shower sump use this
through hull.

Everyone has me convinced that it is there to avoid water being forced in
when pounding up wind. I should probably just replace the hose with new
stuff and put it all back in.

Thanks everyone for the input.

[thinwater]

Originally Posted by MooGroc

I should probably just replace the hose with new
stuff and put it all back in.

Thanks everyone for the input.

Actually, you may want to do a little re-plumbing to eliminate the kink. But I wouldn't lose sleep over it.

My case is a little worse. It is a multihull, and when going to windward, the lee hull is pressed deep AND it is NOT heeled. Thus, the drain really gets blasted.

[sailcrazy]

Although all our sink,shower, and galley drains are below the waterline, some are deeper than others. But when we're on the anchor or a mooring ball, and the waves kick up, you can easily hear the "wheezing in and out" sound. We've tried putting the stopper in, or the stopper with the bowl filled with water, and neither stop the "wheezing". sooner or later the air pressure buildup pops the stopper out, the sink drains and the noise continues. We just ignore it. BUT....I would like to know the best way/how to clean those 1-way check valves. Ours are all metal, but the connecting hoses are rubber.....I've been reluctant to try any drain cleaner product, and so far I have not been aable to get them loose-either the valve access on top or the whole assembly. any ideas???

[Cheechako]

Probably to avoid taking in water on heel. You should have a seacock though. IMO most schemes to reduce number of seacocks in a boat are more dangerous than more seacocks.
I'm definitely not a fan of check valves in a shower sump drain as there is usually a lot of hair etc and the check valve will fail from that.

[buzzstar]

Originally Posted by MooGroc

I've attached a picture of the hose. What I don't like about it is having so many
clamps and complexity. Seems safer to have a straight run to the sink drain.

But I suspect that's the price to pay for having the shower sump use this
through hull.

Everyone has me convinced that it is there to avoid water being forced in
when pounding up wind. I should probably just replace the hose with new
stuff and put it all back in.

Thanks everyone for the input.

Best guess: two of the clams are actually extras, or at least redundant, and nice to have if one of the two on each side should happen to fail.

[hamburking]

Originally Posted by MooGroc

I like the OP's theory that it could be to avoid problems when
heeling. Still, I think I'd have to be heeled VERY far over before
water would enter the sink...

Its not just the level below water, but also the force of water pushing on the hull, since the head is forward (it's forward right?) and the boat pushes through the water. I was surprised one windy day, when my crew left the valve open on the head, which was well above the waterline, and it had been siphoning into the cabin. Several inches of water to pump out and a lesson learned.

Your instinct to keep the thru hull valve closed is a good idea.

[Oceanride007]

I would say it is there, to avoid syphoning. That is, although the skin fitting is above water level, maybe not always. Ships do the same but they are of a design that doesn't clog. in which case it is a "classification society" thing.

My boat has a arrangement that other o'boards, (3 bilge and shower drain), are collected in a "high up" common tank and a largish pipe drains to the transom. Does the same thing as a vent loop, my tank is just under the top of the companionway.