Joker Valve

Alan Leslie

I never really understood why they called it a "Joker" valve, now I think I know: it is a joke, it doesn't work!

I've replaced this valve in both heads twice now and the bowls still slowly fill with backflow from the pipe to the holding tank.

Does anyone have any ideas on how to stop this, or have i just got a bad batch of valves ?



Elyse SM437 


Ian Park

Check your anti siphon loop valves. The little rubber valves on mine perished, stuck together and stopped the anti siphon from working. Much nicer job than cleaning out the 'jokers'.

Ian. 'Ocean Hobo' SN96


Hi Ian.
I'm not familiar with the valves you're referring to. Where are they?

Ian Park

On the hose from the sea cock. It is usual to have a loop in the flexible pipe taking it above the heeled water line. There is usually  plastic 'u' bend clamped on to the up and down pipes to form the u shape. This bend should have a small screw cap (like a car tyres valve). Inside is a tiny rubber non return valve. It allows air into the pipework to prevent the motion of the boat pumping sea water back up the pipe until it siphons back into the toilet.


Craig Briggs

Here's a link to a great article on joker valves in Practical Sailor.

Joker Valves for Marine Heads - Practical Sailor Print Edition Article
Happy Flushing,
Craig Briggs, SN#68, Sangaris, SanDomingo Creek, MD