Strange Vaccuflush issue

RWS

RWS

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Rebuilt EVERYTHING in 2006

for the last 15 years, Pump never cycled at all.

You could shut down the power and the vacuum would still be holding a week later

all of a sudden...... cycles on/off about every 5/10 minutes

replaced both duckbill valves - no joy

added butyl tape to those joints, and tightened all accessible hose clamps

no change

Verified that the bowl seal is NOT the source of the vacuum leak

Suggestions?

RWS
 
First make sure the new duckbills aren’t twisted. This will happen if you overtighten the fittings. I always used liquid soap on the flanges to prevent deforming them

try listening for the leak at the base of the bowl or at the pedal seal

another potential issue is the vac switch. Sometimes with age they rod gets corroded and they stick. Or the seal gets bad. If the switch assembly is 15 years old... I wouldn’t be surprised. Environmental Marine in FTL has the best prices and service in VF parts

of and although not likely to be the source of cycling, the bellows usually fail at 15 years... usually a messy failure with “stuff” being squirted out :(
 
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Time to replace the diaphragm in the pump
 
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I had a similar issue. Spent hours on the phone with dometic. I found the issue by removing the toilet and corking the base. It never lost vacuum. Turned out to be the seals in the actual vacuflush mechanism at the pivot point. Once I replaced the mechanism (very expensive). Problem was solved.

Ken
 
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The seal in the ceramic head is fine.

Verified by leaving only a teaspoon or so of water around the seal with the unit holding vacuum - no loss of water

I will check the duckbills and reinstall

This pump is only 2 years old, the previous one was FACTORY and believe it or not, lasted 35 years

I put a label on the pump this time that says INLET AND OUTLET ARE REVERSE THREADS as I had a problem with that

RWS
 
And i'm back...

Checked for twisted duckbills as Pascal suggested - no change

checked for "leaking sounds at and around the head - not even crickets

replaced the vacuum pump with new - new pump cycles exactly as the old one

every 55 seconds

Suggestions are appreciated

RWS
 
The bowl could leak without pulling the water down. Is the bowl secure without any rocking etc.? Tighten the big clamp, and check for leaks at the pedal axel. How about the vacuum switch? The pump could be leaking as well as pointed out earlier. Give it a close up sniff LOL.
 
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As I stated earlier, Dometic technical support told me to pull the toilet and cork the base plate. If it holds, you will know it is somewhere in the toilet connections or the mechanism itself. Ours held water yet it was still leaking from the mechanism.

Ken
 
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Indeed if you can pull the bowl and plug the hose going back to the pump that would certainly shed some light if the vacuum held.
 
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I rebuilt all the components during my 2006 refit

Of course, they are all now 15 seasons old

The ceramic bowl is not easily removed - did this 15 years ago when I rebuilt the system

If the leak was at the toilet, or beneath i would suppose a leakdown cycle of 55 seconds would make it easy to hear, but no noises in the toilet area.

Also, no smells whatsoever

This design has the separate "torpedo" style tank, but it is difficult to access.

Might be easier to crawl in there and replace the vacuum sensor.

Do you think I am on the right track?

RWS
 
I don’t think throwing parts at a problem qualifies as being on the right track. Especially expensive parts like a vac pump. Or the vac switch.

problem could be the hose connections to the vac tank but unlikely unless they ve been disturbed. I ve never seen a leak at the vac switch but that’s possible.

I still bet on the bowl itself. Either the base seal or something else under the ball valve
 
Pascal is most likely correct. I did not hear or smell anything when ours was doing the same thing. I would never have narrowed it down unless I removed the toilet and corked the base plate.

Ken
 
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BTDT with the vacuum accumulator tank and the pressure switch. Major PITA. On the Hatteras we had, there was a "night switch" in the heads that shut the pump off. That way it never cycled over night. Try shutting off the pump for a while, like a few days. Then see if you have enough vacuum to flush (without using it LOL). If you still have vacuum I lean in the direction of the vacuum switch.
They call it the 13 year switch by the way. It lasts 13 years and then croaks..
 
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Hey guys, I agree with the THROWING PARTS AT IT concept, however I carry a spare pump onboard and it's a relatively easy item to swap out. I even added a quick disconnect to the electrical side.

This boat is equipped with a night switch.

There is a small horizontal inspection plate to the left of the bowl.

I have one of those mechanical stethascopes - might be worth a try before all the difficulties of removing the bowl assembly

Maybe I should cut a hole in the fiberglass base and add an big ass inspection plate?

RWS
 
There are different types of bases for Vacuflush with different hose connections. I remember one I had back on a 1999 boat... it had a soft rubber seal at the base which could easily be crushed and leak of over tightened. Others bases just had a PVC hose sticking out of the base. Usually it s all above the floor
 
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i believe mine looks like the photos in this thread (not my boat):


a piece of piano wire would cut through the 4200 holding the china bowl to the fiberglass base

just hate to tear into all that if the leak is elsewhere........

PLUS - if I have to take it all out, I damn well better replace every soft part thats in there

RWS
 
If I recall correctly, there is a large hose clamp around the ring that holds the two pieces together. However, the lower half of the bowl assembly houses the ball valve assembly. So unless the whole bowl comes out and gets plugged that test won't happen unless the ball valve assembly gets pulled so you can plug the base.
 
I read on another forum that the pedal shaft seals can leak and be hard to diagnose?
 
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