Marine Sink Check Valves

[yachtgemini]

postscript

Sorry if this sounds like teaching anyone to suck eggs.

Plastic may be OK for valves on sinks in the heads, but my preference remains good quality bronze.

However, think carefully before any changes to the galley sink.

The Tayana 47 galley sink is above the engine in most configurations. Clearance depending on which sink was installed is as little as 18 inches above the engine and heat degradation of any plastic valve and fire issues should be considered in your choice of materials. Original sinks were ceramic and fittings all metal and pipe work fairly heavy (read flame retardant) exhaust type hose.

We cruised for a l o n g time and had an alternator go up in smoke during the first year which scared the hell out of me and made me very careful about materials in the engine room. We simply had lots of smoke and burnt insulation but it was scary enough.

Ross

[MV Caroline]

Originally Posted by Matairea

All three of the sinks (two heads and galley) on our Tayana 47 discharge below waterline and are fitted with swing check valves, presumably to eliminate the "fountain effect" in heavy going.

These check valves are close coupled to the sea cock and predictably, are totally frozen in place mid swing by marine growth/ calcium buildup. This particular seacock was frozen and I broke the handle off resulting in the whole assembly needing to be removed from the boat. It was actually doing it's job because it let the sink drain well enough but blocked the line enough to stop a fountain.

Questions: Are check valves on marine sinks typical and needed? A search brought up very little on the topic. I'm wondering because my usual sources (Defender, Hamilton, Jamestown) do not carry or list what I think is the needed, modern replacement. They have the Groco PNC-1000 (0.45psi opening pressure) but I think I need/want the CV-100 (0.19psi opening pressure). The bottom of the sink is probably 2.5/ 3 feet above the seacock if I had to guess.

What is the standard configuration to solve this problem? Shouldn't the check valve be above the waterline so it does not see marine fouling?

As a side note, to get the thru hull out I took a grinder to the outside mushroom and ground it off. The heat softened the sealant and a few blows of a hammer pushed the the whole assembly into the interior. Way easier than than the alternative for a thru hull I knew I was gong to replace adn located in a very tight spot. In doing this I found that the hose to check valve connection was made with a threaded nipple instead of a proper hose barb fitting. The nipple sheared off flush with the check valve with very minimal force and I found the metal to be highly degraded. It lasted nearly 30 years so I don't think it was brass but either way it was a boat sinking waiting to happen. Pretty scary.

Plastic in-line check valves work much better for this application than the older bronze types. they do not typically "lime up" and freeze in any one position. I placed them closer to the sink end of the discharge so they don't grow barnacles or coral. The one thing that still needs to be addressed is hair and other gunk. I use a simple drain screen in all my sink and shower drains to help prevent clogs further down the discharge lines.

[Stu Jackson]

Have you considered just putting the sink stoppers in the drains?

[David B]

Originally Posted by Matairea

All three of the sinks (two heads and galley) on our Tayana 47 discharge below waterline and are fitted with swing check valves, presumably to eliminate the "fountain effect" in heavy going.

These check valves are close coupled to the sea cock and predictably, are totally frozen in place mid swing by marine growth/ calcium buildup. This particular seacock was frozen and I broke the handle off resulting in the whole assembly needing to be removed from the boat. It was actually doing it's job because it let the sink drain well enough but blocked the line enough to stop a fountain.

Questions: Are check valves on marine sinks typical and needed? A search .

Not required.
The seacocks should be closed before going to sea.
Relying on a check-valve (that inevitably won't ....) is asking for trouble. Also, operating those seacocks regularly - all of them, is important to avoid seizing.