Cockpit drain ball valve and skin fitting

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RJJ

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Hi everyone. Skin fitting project continues...now onto the cockpit drain which gives me another puzzle. The current arrangement is both sides join in a Y to a single tube, which then exits via a 90 degree plastic skin fitting below the waterline. Just off-centre, with no ball valve of any kind. There's not much "drop" between the drain and the skin fitting.

I am unhappy with this, particularly the last part. Questions, please:

1. Is a plastic skin fitting below waterline ok? I was minded to replace with DZR or fibreglass, but have yet to identify a 90 degree one...implying if I change it, it has to be a vertical fitting that will affect the (already-limited) drop.

2. Am I right in thinking a ball valve is essential, being below waterline? True that the valve would always be left open unattended...

3. If I changed the layout (to skin fitting/valve/90 degree tail), the hose would no longer be a direct downward path to the sea...but since it's below the waterline, perhaps this doesn't matter?

Any thoughts, or other options most welcome.

Thanks
 
I can think of no logical reason why you would want to fit a valve in a cockpit drain, unless you wanted a small pool.
 
No reason not to have plastic fittings below the waterline. Many people would suggest using plastic for all skin fittings and valves/ seacocks Tru Design now seem to have taken over from Marelon as favourites

Personally I dont have valves on my cockpit drains ..... The boat I crewed for many years had then but they were never closed and eventually became inoperable.

The less bends the better . ... less restriction of flow and less likely to get blocked. Make the connections from cockpit to outlet as direct as possible.
 
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VicS said:
No reason not to have plastic fittings below the waterline. Many people would suggest using plastic for all skin fittings and valves/ seacocks Tru Design now seem to have taken over from Marelon as favourites
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It's plain old nylon, not snazzy reinforced plastic like trudesign or marelon which I am fitting elsewhere.
 
If it’s been there for years and you’re going to fit a new one, then the new one will last for years before it need replacement..... I think you’re over thinking things. The main thing that cause through hull fitting to fail is degradation of the material they’re made of. Plastic (of any sort) won’t corrode, under the hull it won’t get much (if any) UV to damage it and if the pipework doesn’t impose any undue stress on it it won’t break.
 
duncan99210 said:
If it’s been there for years and you’re going to fit a new one, then the new one will last for years before it need replacement..... I think you’re over thinking things. The main thing that cause through hull fitting to fail is degradation of the material they’re made of. Plastic (of any sort) won’t corrode, under the hull it won’t get much (if any) UV to damage it and if the pipework doesn’t impose any undue stress on it it won’t break.
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Thanks Duncan. Fair enough...but leaves me wondering why we then spend money on ball valves and much stronger fittings for our other through-hulls...? Which I have just done ?
 
I think the big difference is that you can close the others when you leave the boat. Leaving cockpit drains closed over the last winter would have come close to sinking my boat! One advantage of having a valve is that it allows maintenance - replacing the pipes and so forth - to be done in the water without stress.

Having said that, the cocks on my drains are gate valves. The outsides appear to be bronze or DZR - they get a good thwack with a soft hammer every year or so and don't move - but the innards have disintegrated. Ideally, I'd replace 'em, but access is awkward and I haven't been able to shift any of the nuts, so I've tied suitable wooden bungs to them and ignore them. If I had to change the pipes afloat, I could, at the cost of a few litres of water coming in, but it would be easier with working cocks
 
OK. Through hull fittings for things like heads and sink drains need to be closed on occasions for maintenance and the like, also when leaving the boat in the water for any length of time because they don’t need to be open when left unattended, whereas the cockpit drains must be open at all times.
As soon as you fit a valve to the fitting, it needs to be robust enough to sustain repeated loading as you open and shut the valve: think of how much effort it can take to get the valve moving. So you need a more robust fitting for that reason, hence DZR brass or fibreglass fittings.
 
I've had drains with and without valves. I prefer to have them, I was always slightly worried that a pipe would split and there would be no way of checking the flow.
I also prefer metal below water line for valves and skin fittings due to better mechanical strength. (DZR of course)
 
Assuming your boat is GRP think about getting some GRP tube and GRP pipe elbows and glassing the tube and fittings to connect the cockpit drain to the transom outlet as a permanent connection.

You could also add some bracing if the strengthen the connections to the hull and the underside of the cockpiy floor/

I have some "stand pipes" welded to the hull to above waterline so even it the PVC hose breaks its above the waterline so no water ingress.
 
I am tending towards a real skin fitting followed by DZR elbow and ball valve and appropriate hose tail.
 
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