Sink outlet seacock question

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Boo2

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Hi,

I intend to fit a new sink outlet just above the waterline with a loop up to just below the deck level and need to know whether it is acceptable to attach a 90 degree bend to the skin fitting with the seacock attached to that, or is it preferable to have the seacock directly attached to the skin fitting and the 90 degree bend inboard of that ?

It would be a neater fit with the 90 degree bend attached to the skin fitting so I will do that if all things are equal.

Thanks,

Boo2
 
I assume that you are fitting a pump between the sink and the outlet as it won't self drain with a loop up to th gunwale in it...

And yes, it's acceptable to put an elbow joint between the skin fitting and the seacock. The only people who will object are those who probably don't believe in through hull fittings, but in the real world of boat building its not an unusual practice.
 
My heads outlet has an elbow between skin fitting and valve. This lets the valve lie close to the hull where it's less likely to be damaged or strained, and the elbow is just as strong as the skin fitting (actually probably stronger). It's important to cut down the length of the skin fitting to just long enough to reach through the hull, take the securing nut and a locknut for the elbow, screw into the elbow, and leave a few millimetres spare. This gives a compact structure presenting less leverage for any wrenching forces, vs a long untrimmed through-hull.

You're fitting a pump to this outlet, I take it :)

Pete
 
prv said:
Presumably his sink is below the waterline (either full-time, or when heeled) and if he doesn't then the water will come in.
Click to expand...

So he'd need a vented loop too then.

Edit: If the OP has a UFO34, I'd be surprised if the sink is below the waterline when heeled.
 
Last edited:
Halo said:
Why not fit a 90 degree skin fitting
e.g
http://www.ecs-marine-equipment.co.uk/marine-equipment/skin-fitting-90-degree-item-3950-PK.html
(no connection)
Click to expand...

They come in two parts - the through hull and the 90 degree are separate but sold as a single unit.

I had the same issue as the OP and after deliberating fitted a right angle prior to the seacock to keep the lay of the pipe parallel to the hull. The only problem was ensuring the angle ended up pointing in the right direction when everything was tightened up.
 
Boo2 said:
Yes, I'm fitting a Whale Gulper pump and the corresponding Whale holding tank under the sink.
Click to expand...

OK. I'm curious why, though - unlike a classic long-keeler sitting deep in the water, as pvb says it seems unlikely that the sink in a UFO would be near the waterline.

Pete
 
pvb said:
prv said:
pvb said:
Why have a loop up to deck level?
Click to expand...
Presumably his sink is below the waterline (either full-time, or when heeled) and if he doesn't then the water will come in.

Pete
Click to expand...
So he'd need a vented loop too then.

Edit: If the OP has a UFO34, I'd be surprised if the sink is below the waterline when heeled.
Click to expand...
The current arrangement is for the sink to drain directly to the cockpit drain (above the seacock) with hand diaphragm pump so I don't know whether it is above the waterline or not. The surveyor said to change this arrangement as it could sink the boat if the sink pipe came adrift or became punctured.

I prefer a loop just in case anything goes wrong, the Whale Gulper pump is a diaphragm type so really the loop is belt and braces, I admit. If anyone thinks it's daft then please call out and I can reconsider.

Boo2
 
Boo2 said:
The current arrangement is for the sink to drain directly to the cockpit drain (above the seacock) with hand diaphragm pump so I don't know whether it is above the waterline or not.
Click to expand...

Does seawater flow into the sink? If not, it's above the waterline.


Boo2 said:
I prefer a loop just in case anything goes wrong, the Whale Gulper pump is a diaphragm type so really the loop is belt and braces, I admit. If anyone thinks it's daft then please call out and I can reconsider.
Click to expand...

I think it's unnecessary expense and complication.
 
I wonder if you're heading for syphoning problems with a pump delivering to a potentially submerged outlet over a looped pipe.
If you operate the pump whilst the outlet is submerged, there is a possibility of a back-syphon starting up when the pump stops, if the pump valves aren't tight. With sink waste going through them, that seems quite likely.
A syphon break seems to be called for.
 
Boo2 said:
The current arrangement is for the sink to drain directly to the cockpit drain (above the seacock) with hand diaphragm pump so I don't know whether it is above the waterline or not. The surveyor said to change this arrangement as it could sink the boat if the sink pipe came adrift or became punctured.
Click to expand...

Well, how much of the body of your boat is below the water? I don't know the UFO, but I'd hazard a guess it's only 18 inches or so. So unless the sink is down by your knees, it must be above the waterline.

I don't really understand the surveyor's point. Yes, if the sink pipe leaked below the waterline then water would come in until you closed the seacock - but the same applies to the cockpit drain hose too. I guess if there's a long run of sink pipe through lockers etc then it's more vulnerable than a short vertical run of cockpit drain pipe, but I'm assuming the reason they're teed together is that the sink is on the aft bulkhead of the cabin, right next to the drain.

Either way, if you wanted to separate the sink from the cockpit drain, the usual solution would be a new seacock just below the waterline, and a simple length of hose to it from the sink. No space-hogging tanks or blockage-prone pumps.

Pete
 
Boo2 said:
The current arrangement is for the sink to drain directly to the cockpit drain (above the seacock) with hand diaphragm pump so I don't know whether it is above the waterline or not. The surveyor said to change this arrangement as it could sink the boat if the sink pipe came adrift or became punctured.
Click to expand...

My Pegasus has the same arrangement - the main sink pipe leads to an outlet within the skeg. Since the boat has not yet been in the water during my ownership I'm not 100% sure if this outlet is above or below waterline, its certainly very close to it. There's no possibility of adding a seacock in this particular position and even if it were possible its so hard to get to it would be unusable. The forward cabin sink was originally led directly to a skin fitting just below waterline and it was this one that I spotted was a potential hazard so added the seacock and doubled up on pipe clamps. This thread now has me wondering if I should block off the skeg outlet and put a separate skin fitting with seacock where it can be reached to service the main sink.
 
Boo2 said:
The current arrangement is for the sink to drain directly to the cockpit drain (above the seacock) with hand diaphragm pump so I don't know whether it is above the waterline or not. The surveyor said to change this arrangement as it could sink the boat if the sink pipe came adrift or became punctured.

I prefer a loop just in case anything goes wrong, the Whale Gulper pump is a diaphragm type so really the loop is belt and braces, I admit. If anyone thinks it's daft then please call out and I can reconsider.

Boo2
Click to expand...


the cockpit drain pipe might also "come adrift", where does one stop. dont forget KISS
 
If you are making an extra hole in the boat I would stick with the way of the vast majority. A simple pipe down from the sink to a seacock directly below. If water comes up into the sink (almost never would come over the top of it) when heeled hard over, then shut the seacock - if very cautious then shut the seacock when leaving harbour.

No pump, no loop - simpler and easy to use as a sink.
 
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