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-   -   Joker Valve? (http://www.sailnet.com/forums/gear-maintenance/69644-joker-valve.html)

WanderingStar 11-04-2010 06:17 PM

Joker Valve?
 
I replaced it because it let the water in the hose back into the bowl. I used an expensive Thetford, spec for the WC Skipper head. It still lets water back in. Might I have overtightened the bolts?

mgmhead 11-04-2010 06:46 PM

Doubt the bolts are too tight. Could you have installed it backwards?

MJBrown 11-04-2010 07:03 PM

Unfortunately I've had brand new ones leak on me. Check to make sure the tank vent hose is clear as well. If it's clogged you can get back pressure which will force water back through the joker valve.

GaryHLucas 11-04-2010 07:42 PM

What a great name for a valve used in raw sewage! The joker valve would have to be really special to stop water from leaking back through when it passes Sh..., toilet paper, etc. Any tiny little piece and the valve isn't going to close completely. However the real purpose of that valve is to make the reciprocating pump work, not keep the water from flowing back. As long as most of the water passes through the valve and doesn't come back then the pump works fine. If the valve stays completely open water will just reciprocate back and forth in the hose along with the pump piston.

So you are going to get some water back, and about all you can do is pump vigorously to make most of the water in the hose go over the vented loop into the tank. You DO have a vented loop in the hose right?

Gary H. Lucas

sck5 11-05-2010 07:40 AM

what a crappy problem!!!

yuk yuk yuk

JimsCAL 11-05-2010 07:41 AM

Is there a vented loop between the head and holding tank?. If not, adding one will probably solve the problem.

svHyLyte 11-05-2010 07:44 AM

If fact, one can over-tighten the bolts holding a joker-valve in place and, if the flange for the collar is not perfectly flat, that can spread the lips enough to allow leakage, particularly it the water column is not great enough that the water pressure forces them closed. It really doesn't reguire much torque on the bolts to create a water-tight seal around the collar base.

FWIW...

WanderingStar 11-05-2010 09:02 AM

Thanks all.
Hylyte, I'll loosen them until it leaks, then tighten them til it just stops.

Cruisingdad 11-05-2010 09:15 AM

If your tank is not venting well, when you pump it, you may get it bleeding back into the bowl. Also try taking off the deck cap so it will breathe. See what happens. That will only take seconds. If it does not go back into the bowl, you know your problem.

olson34 11-05-2010 09:32 AM

It's no Joke
 
Quote:

Originally Posted by svHyLyte (Post 663246)
If fact, one can over-tighten the bolts holding a joker-valve in place and, if the flange for the collar is not perfectly flat, that can spread the lips enough to allow leakage, particularly it the water column is not great enough that the water pressure forces them closed. It really doesn't reguire much torque on the bolts to create a water-tight seal around the collar base.

FWIW...

Good advice on how much to tighten those bolts.
I have owned boats with marine heads for almost three decades. No "joker" valve ever leaked back regularly. Once in a while we can tell that a tiny piece of paper is hung up in the valve though, by the slow back filling at the bottom of the bowl.

Lots of folks turn off the head discharge thru-hull when not using the head; we turn it off only when leaving the boat.
(None of our boats ever has had a vented loop on the outflow... but that does not mean it is a bad idea.)

L


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