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Pamojo 02-18-2013 12:40 PM

Head Backfill
Hey! I have an issue I've been trying to resolve around water entering the head through the toilet when it is on the low side tack.

Setup - Inflow - Through hull seacock to strainer to ball valve to head.
Outbound - Head to macerator pump to check valve to Electrosan w/2 vent loops to 3 way valve to overboard seacock OR to holding tank.

All is good when the boat is flat or head is on the high side. I've tried shutting everything and diverting to the holding tank but I still get waste water in the head on the unfavorable tack.

I've replaced the ball valve and the check valve - still the same. Thoughts?

mitiempo 02-18-2013 05:19 PM

Re: Head Backfill
1 Attachment(s)
You need to install a siphon break between the head pump and the back of the bowl to prevent flooding. Another anti siphon should be installed between the head and through hull on the output side if it does not go directly to a holding tank.

pdqaltair 02-18-2013 06:54 PM

Re: Head Backfill
Sounds like he already has vented loops.

"Entering the head through the toilet" is unclear to me, since to most people the head is the toilet, though you could mean it is overflowing into the compartment. Is it waste or seawater? I assume from the title you mean backflow of waste.

It is very likely a simple matter of not flushing enough water. That is the root cause of most backflow problems; urine sits on the joker valve, deposits build, and the valve becomes blocked open. This can happen as quickly as a few months but generally a few years. If enough is flushed, deposits don't build since the process requires reaction time. Additionally, if waste comes back, by definition, not enough was flushed.

If it is doing more than refilling the bowl then there must be a siphon issue. Assuming there is a vented loop, I would guess the vent is clogged, common enough on waste lines. It can also be a matter of wave impact; on my boat the shower sump loves to backfill on one tack if it's rough enough long enough. The waves and pounding are just enough to make the check valve flop around enough, and the waves are striking the through-hull.

One tack vs the other may be the location of the tank or some asymmetry of the plumbing, rather than the actual cause. Couldn't say without a lot of detail.

Faster 02-18-2013 10:24 PM

Re: Head Backfill
According to Peggy Hall "Headmistress":


This means that TWO vented loops are required in the discharge--one between the toilet and the the treatment unit and a second one between the treatment unit and the thru-hull. Both loops need be high enough to be at least 6-8" above waterline AT ANY ANGLE OF HEEL...if you put 'em too low, they won't solve the problem.
Not clear from the OPs description of this is what he has exactly....

Pamojo 02-19-2013 05:48 PM

Re: Head Backfill
There 2 anti siphon loops - 1 before the Electra San and 1 after. The system is under the v-berth forward and the loops come to the bottom of the berth. There is also a check valve after the macerator pump.

I hit the system with the muratic acid cleanse twice a year so it shouldn't be the joker valve. I don't know anything about it but it's not funny.

The flush is electric and runs for 30-45 seconds and leaves the bowl clean when done.

The head has overflowed in rough conditions - don't know whether it was just slosh or a lot of backfill. It did this with all the valves closed and the y valve diverting to the holding tank.

Faster 02-19-2013 06:01 PM

Re: Head Backfill
The loops probably need to go right up to the underdeck for proper protection.

pdqaltair 02-19-2013 07:53 PM

Re: Head Backfill

Originally Posted by Pamojo (Post 992400)
I hit the system with the muratic acid cleanse twice a year so it shouldn't be the joker valve. I don't know anything about it but it's not funny.

I hear that a lot--but it doesn't quite work that way. Unless you disassymbled the head, you don't know if all areas are clean. They also lose elasticity. There are chemicals that folks use that cause damage (PG, baby oil, Lysol, certain holding tank treatments including those with formaldahyde). If it is over 1 year old and you have these symptoms, it is very likely the problem or at least is dismissed as a cause at your peril. If the valves were all closed, where could water come from but the large diameter hose to the tank?

Conventional wisdom holds that "joker" is a bastardization of "choker," but who knows.

Pamojo 02-20-2013 10:55 AM

Re: Head Backfill
Hey! I'm going to to replace the joker/choker (really should be the gag valve) valve and raise the vented loops. We will see if that works.


RobGallagher 02-20-2013 11:22 AM

Re: Head Backfill
My money is on the joker valve. Damn things stretch and no amount of acid will counteract that.

pdqaltair 02-20-2013 01:24 PM

Re: Head Backfill

Originally Posted by Pamojo (Post 992663)
... (really should be the gag valve)...


Yeah. Not much funny about that.

Actually, if you flush with water (and some folks like to add some vinegar) numerous times before you start it's no big deal.

Note that the slit goes vertically--this reduces sagging.

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