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Old 28-10-2019, 13:29   #1
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Sealand vacuflush - order of items to check for leak.

A while back the vacuum pump was coming on about ten to fifteen minutes after a flush. Been a couple of years since the duck valves were replaced, so I replaced both of the two valve pairs (forward/aft or pre/post which ever you call it) of the vacuum chamber.

That added about five minutes to the time between pump cycles, so obviously there's a leak somewhere.

Bowl holds water, so I'm pretty sure the leaks not there.

Guessing the next step is to do the soapy water/shaving cream check on each hose connection.

If those show no leakage, do I assume the bellows or pressure switch? How do I test those? Which one to check first. TIA.

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Old 28-10-2019, 14:40   #2
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Re: Sealand vacuflush - order of items to check for leak.

If the bowl holds water, it is not the bowl seal.

If you have new duckbill valves, it is not the bellows, it would not leak back to the vacuum chamber past the duck bill valves, and if the bellows leak, they will leak OUT when pumping "stuff" so you'll know...

First step is to tighten ALL the hose clamps between the toilet and the pump. Really tight. If any break, replace them with good ones.

If your duck bill valves were "years old" they were surely part of the problem. Check carefully the mounting of the duckbill valves and connections on the vacuum side of the pump.

Do NOT mess with the vacuum switch! If you start fussing with that, getting it to work right again is very difficult. Just tighten the hose clamp securing it. Do NOT try to adjust it.

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Old 28-10-2019, 18:02   #3
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Re: Sealand vacuflush - order of items to check for leak.

There is a seal that the toilet sits on. That fails too.

Number 15 in the diagram.
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Old 28-10-2019, 19:45   #4
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Re: Sealand vacuflush - order of items to check for leak.

If you've replaced the duckbills and made sure you can't see ANY daylight when you hold one up to the light to check,the pressure switch is the most likely culprit. There's a very small rubber diaphragm in it that develops a pinhole leak with age. It starts out by behaving like a worn duckbill valve does--causing the pump to run between flushes for no reason...running a little longer each time until finally the pump won't shut off after a flush at all. Billknny gave you good advice: do NOT mess with it or try to adjust it!

It would be nice if you could replace just that li'l diaphragm, but no such have to replace the entire vacuum switch. And it's only available from one of the Dometic (formerly SeaLand) regional "authorized VacuFlush dealers." There's at least one in can spend an hour trying to find it on the Dometic website, so call Dometic in Ohio for location of the one nearest you. 800-321-9886

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Old 29-10-2019, 09:11   #5
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Re: Sealand vacuflush - order of items to check for leak.

I found another source of a leak when I developed a symptom like yours. It was the fitting where the curved hard plastic hose goes into the tank. The seal started leaking. I removed it and cleaned it and rebedded it with caulking and that solved the problem.
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Old 29-10-2019, 13:50   #6
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Re: Sealand vacuflush - order of items to check for leak.

I have chased down many supposed leaks on my vacu flush’s to no avail.
Eventually I pulled out the ball valve shaft and replaced the small o ring and problem solved!
The systems now hold vacuum for days on end.
I have also found that smothering shaft seal and spring cartridge assembly in petroleum jelly or a lanolin grease adds significantly to length of time between new o rings.
Keep the old o ring measure it up and take it into a bearing supplier and you will buy them for 10 cents each rather than the whole valve kit that Dometic will sell you.
This is the first thing I now look at when vacuum generator pumps start short cycling.

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