Toilet syphoning dry.

[ABQLD]

Hi from Australia.
Some guidance from the group would be greatly appreciated.
I have a TMC electric toilet fitted to my cruiser and it’s misbehaving.
The boat has a holding tank and a Y valve that is set to “overboard” and the toilet set sits above the waterline.
Recently the bowl started overfilling during the flush process.
More water was coming in than going out.
When I checked the Y valve it seemed to be almost in a 50/50 position between holding tank and overboard.
I pulled the Y valve apart, cleaned it and reset to to the overboard position which then gave me the opposite problem of the bowl syphoning completely dry after it is flushed.
This morning I replaced the flapper valve for good measure however the syphoning effect simply pulls the flapper open.
As the toilet is above water level there is no anti syphon loop in the outflow hose.
Anyone else been down this road?

[GILow]

That loo is very prone to salt build up, flush it well with vinegar and see how it behaves.

I run a vinegar dose through mine every two weeks to avoid unspeakable problems.

Cleaning vinegar is dirt cheap.

[ABQLD]

Thanks GILow.
It sounds like a good practice.
Unfortunately if I’m understanding you, until I can find out why it’s siphoning dry that vinegar is just to end up in the drink.

[sailorboy1]

Was the head filling while flushing, or when dry bowl pumping.

If only while flushing maybe you hoses are clogged

Vinegar wouldn't unclog a line unless you have 100 gals

[ABQLD]

Originally Posted by sailorboy1

Was the head filling while flushing, or when dry bowl pumping.

If only while flushing maybe you hoses are clogged

Vinegar wouldn't unclog a line unless you have 100 gals

Once the pump is engaged it pumps normally, the bowl fills with an appropriate level of water that is then pumped out.
The problem is syphoning.
Once you release the power switch the water continues to drain out of the bowl until it’s completely empty.

[GILow]

Originally Posted by sailorboy1

Vinegar wouldn't unclog a line unless you have 100 gals

I used to think that too. But a friend recently did the vinegar/bicarbonate combo on her blocked TMC and it actually unblocked the line. I can’t figure out how it could have worked but I saw the results for myself and there’s no doubt it did work. (I recommended she stand back, that’s for sure.)

[sailorboy1]

Originally Posted by GILow

I used to think that too. But a friend recently did the vinegar/bicarbonate combo on her blocked TMC and it actually unblocked the line. I can’t figure out how it could have worked but I saw the results for myself and there’s no doubt it did work. (I recommended she stand back, that’s for sure.)

it blew out the line, but did not dissolve the scale

get some scale and put it in bowl of vinegars and find out

[peghall]

I don't think the water is siphoning out...I suspect gravity is causing it to drain out.

Most marine toilets aren't designed to hold any water in the bowl after flushing...this is because the water is likely to end up all over the head when tossed around by heavy seas or even wake. You can plumb it to hold water...a loop in the discharge line ahead of the y-valve that's higher than the bowl (how much higher depends on how much water you want to be left in the bowl). Just be sure to flush long enough to make sure that the water running down from the top of the loop is clean.

You may find other suggestions to accomplish this in U-Tube.

--Peggie

[GILow]

Originally Posted by sailorboy1

it blew out the line, but did not dissolve the scale



get some scale and put it in bowl of vinegars and find out

It did both mate, there was vinegar in there too.

[sailorboy1]

waste of time to talk chemistry to people who don''t know I guess

[GILow]

Originally Posted by sailorboy1

waste of time to talk chemistry to people who don''t know I guess

Ummm, my chemistry is actually very good. Part of my university degree.