head backflow

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6 years 10 months ago #1529 by George Fogel
head backflow was created by George Fogel
Both of our heads are flowing back into the bowl. I tried replacing the entire pump assembly,
but it continues to leak back.. Biggest problem with this is that if the boat is left for a week or so it will stink to high heaven.
Short of a composting head, any ideas
George Fogel
SailOn

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6 years 9 months ago - 6 years 9 months ago #1530 by George Chamberlain
Replied by George Chamberlain on topic Re:head backflow
- Joker valve torn?
- Line from the head to the holding tank obstructed, so that flushing just builds pressure in the line, and it forces effluent back to the bowl?
- Have you come to a new location - maybe critters in the water when you flush causing a rancid odor - try using fresh water to flush, see if that leaves things cleaner/ fresher than saltwater intake flushing.
- Should be a vented loop in the flushing line - is the vent clogged?

I imagine you have tried most of these already, just trying to think of how it could be malfunctioning...

GAC

Edit - just realized you said BOTH heads are backflowing - is the holding tank vent clogged? On my boat, the head vent was a very long 3/4" line that led to a bronze elbow through the transom on the stbd side just above the waterline. The elbow had a very very small throughput, probably 1/4", and it was plugged. And when I tried to disassemble it to clean it, it crumbled to bits. I replaced it so that the vent line terminates inside the starboard stern locker, into a charcoal filter. Easy to disassemble and backflush with a fresh water hose when we pump out.

If the holding tank vent is plugged, then when you flush the holding tank is just compressing the air in the space above the fill level - the air can't flow out of the vent! The pressure will force the black water back to the bowl. I bet that's it...

If you can get the tank emptied, you can check for this. First, pumping out is problematic, because the same clog will cause the holding tank to form a vacuum and try to collapse it. So be careful not to collapse the holding tank. If you can discharge overboard, you can open the pumpout fitting to use as a temporary vent. (Depending on your location RE: discharge/ no discharge zone.) To test the vent, open the overboard discharge and let the tank take on seawater. Have the wet locker emptied out (assuming your holding tank is in the same place as mine) so you can observe the tank. You will see the tank expanding due to the pressure. Shut the seacock as soon as you see water coming in, or see the tank expanding. Don't let this go too far or you will damage the tank. Unscrew whatever spare fitting you have on the top of the tank, and you will release the air in the tank. If your vent is working, you won't build pressure and you won't hear the air escaping when you open the top of the tank. Don't use the pumpout fitting to test this, as it is plumbed to the bottom of the tank - you won't get air, you'll get a nasty shower of crap.

He who will not risk cannot win.
Last edit: 6 years 9 months ago by George Chamberlain.

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6 years 9 months ago #1531 by Randy Robinson
Replied by Randy Robinson on topic Re:head backflow
It's possible that the housing that your joker valve fits into has calcium build up in it. This would allow back flow because the joker valve is slightly pinched. Its easy to clean, just use a spoon to break it up. I had to do it after 2yrs in salt water.
Good Luck,
Randy

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6 years 9 months ago #1532 by George Chamberlain
Replied by George Chamberlain on topic Re:head backflow
I thought that too, but "both of the heads are flowing back to the bowl", and I assumed that they both started doing this at the same time - has to be a common source of back pressure. Such as, the holding tank vent.

GAC

He who will not risk cannot win.

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6 years 9 months ago #1533 by Randy Robinson
Replied by Randy Robinson on topic Re:head backflow
Something to think about when you say back pressure from the holding tank. Both anti siphon valves would have to be bad in the vented loops for each head. That would not only be odd but diffidently not good.
rr

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6 years 9 months ago #1534 by George Chamberlain
Replied by George Chamberlain on topic Re:head backflow
I thought the antisiphon valve was to prevent a vacuum in the system from sucking in seawater. It would open under a vacuum to break the siphon, but would close under pressure. Or, they could be stuck too - if the vent is clogged, it's not hard to imagine that the antisiphon valves have not been serviced and are stuck. If those valves opened to relieve pressure, it would always stink in the head. In a properly functioning system, the vent releases holding tank pressure (ideally in a place where you won't smell it) and the boat is relatively odor-free.

GAC

He who will not risk cannot win.

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6 years 9 months ago #1535 by George Fogel
Replied by George Fogel on topic Re:head backflow
I am thinking that the joker valves might be the problem here, what is coming back seems to
what has just been flushed. The tank has been emptied. Right now I have a bigger problem
with the engine not running, but I think I've got that one figured out. Condensation in the fuel tanks
due to not using the boat (due to remodeling the house ) and installing A/C on board this spring.
"It's hard to remember to drain the swamp when you are up to your @$$ in alligators!"
George
Sail on

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