Backflow into the toilets in Beneteau 473

Jul 7, 2020
3
Beneteau 473 Fort Myers Beach
Hi Everyone,
I have an electric head in the forward stateroom and a manual head aft. My problem is that I always get backflow into the heads shortly after flushing. I'm sure its because the holding tanks are both behind the heads and the water is lifted about 3 feet into the top of the holding tank. I have replaced the joker valves numerous times, but it never seems to solve the problem. I suspect if I pump enough water through the head to ensure all clean water in the hose, it would be ok, but that is a lot of extra water. I'm thinking of installing vacuum flush heads and hope that will help some. Has anyone encountered this problem and how do you deal with it. Thanks for your input in advance.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Actually, it sounds like the most likely problem I used to have- the holding tanks' vent is blocked. If it is the small thruhull with screens, the screens (TOO) easily get clogged. Put in mushroom thru hulls and hoses about an inch opening. Doubling the diameter quarduples the opening by 4 times.
The nice thing is, you can reverse-flush the vent line from the outside .
 
Dec 2, 1997
8,708
- - LIttle Rock
A blocked vent may be creating back pressure that's preventing flushes from making it into the tank, and Ron gave you good advice to replace the vent thru-hull....but there are other possibilities. Low voltage to electric toilets is a common reason for sluggish discharge, so are worn discharge impellers. Worn joker valves in a manual toilet reduce its flushing "power"...so does a pump in need of a rebuild kit (if it's a Jabsco, just replace the pump instead...it's a lot easier and a "service kit" costs almost as much as a pump assembly. I know a lot of people who replace Jabsco pumps annually as "preventive maintenance").

Assuming that If the tank vent is clear...you don't have to fill up your tanks with flush water to have clean water running back down to the toilet...

Any manual toilet that's working anywhere near factory specs should be able to lift bowl contents up to 4' in the dry mode, so using the dry mode should push bowl contents into your tank...switch to wet only long enough to bring in clean water to rinse the discharge line behind the flush, switch to dry to push that into the tank.

If your electric toilet has only a single flush button, "upgrade" it to one that offers 3 options: bring water in ahead of the flush, dry flush, combination water in/flush out. Always add a little water to the bowl ahead of use, then use the same dry/water in/dry flushing routine as the manual toilet.

--Peggie
 
Jul 7, 2020
3
Beneteau 473 Fort Myers Beach
Thank you both for the advice.... I have replaced the vent hoses. But will look into the other recommendations.
 
Dec 2, 1997
8,708
- - LIttle Rock
If you didn't also replace the vent THRU-HULL, you should...with an open bulkhead or "mushroom" thru-hull (the same kind that your bilge pumps use). "Vent" thru-hulls are designed to use on fuel and water tank vents, to keep sea water out of the fuel and water supply...boat builders use 'em on holding tanks 'cuz it costs 'em less to use the same one on everything. Unfortunately, they're one of the most common location for a vent blockage. An open bulkhead thru-hull not only allows more air exchange with the gasses in the tank--essential in odor prevention--but it also makes it possible to prevent a blocked vent by putting hose nozzle against it and back flushing the vent line every time you wash the boat and/or pump out. And replacing a vent thru-hull is a very inexpensive and easy fix.

--Peggie
 
Jul 7, 2020
3
Beneteau 473 Fort Myers Beach
Thanks Peggie, I have actually already done that. It's a great recommendation. I have actually gone a step further and installed an aeration system in my holding tank that pumps air into it......