Vacuflush pump runs constantly.

[Passages]

I'm at my wits end on this one.

Replaced all duckbills.
Checked all hose clamps
Listened for leaks - none heard
Bowl holds water.
Test flushed to confirm there's plenty of vacuum in the system. There is.
Spent $193 of my favorite dollars for a new vacuum switch.

After all that, I turn on the breaker and the pump still runs and runs. I just touch the knurled plunger on the switch and it shuts off the pump and it stays off. I give slight tug on the plunger and the pump comes back to life but does not shut off. Touch the plunger again applying very light pressure and it goes off. Go to the toilet to test flush and the pump comes to life normally but refuses to turn off. I return to the vac switch, softly touch the plunger and the pump stops.

It's almost as if the system is achieving 95% of the vacuum needed to trigger the vac switch.

What the heck is going on?

 

[Passages]

Thinking this through over a beverage....could it be possible I have a small leak in a hose somewhere that only opens up when vacuum reaches a certain level?

I think the hose is the only thing left to replace...

 

[captcrunch]

Check bowl seal. I had same issue that caused pump to burn out

 

[Leland]

Have you checked the pump diaphragm? I had a split in one once and it caused it to run.

 

[Walter P]

Over the years I have had similar issues and each case it was the bowl seal. Simple fix. One way to
get an idea before you dismantle the head to replace the seal is to take a small piece of Scotchbrite pad
and with the water shut off and the pedal totally depressed, clean the existing seal. If it helps even a
little, then dismantle the toilet and install a new bowl seal. While you're at it don't forget to replace the
seal under the head as well....

Walt

 

[Passages]

Over the years I have had similar issues and each case it was the bowl seal. Simple fix. One way to
get an idea before you dismantle the head to replace the seal is to take a small piece of Scotchbrite pad
and with the water shut off and the pedal totally depressed, clean the existing seal. If it helps even a
little, then dismantle the toilet and install a new bowl seal. While you're at it don't forget to replace the
seal under the head as well....

Walt

Walt, if it was the bowl seal, wouldn't the bowl lose water and start sucking air? This is not the case. Bowl holds water fine.

 

[osprey]

I just replaced the hoses in the engine room going to the two vacuum pumps. Although the toilets seem to flush nicely, neither pump would turn off on it's own. The hoses did not leak liquid but they seemed old and brittle so I replaced them. Both systems now work as advertised, pumps now shut off and system holds vacuum.

Lucky me, P

 

[Pascal]

If water stays in the bowl, the seal is good

A cracked diaphragm will result in black water spraying out

Make sure the duckbills aren’t deformed when the fittings are tightened. I always use liquid soap on the flanges. Don’t over tighten

If the pump stops when you touch the rod on the switch, it s usually the switch. But you said you replaced it... one of mine does that sometimes but the switch is 15 years old

If you had a leak the pump would stop but cycle on and off. It really sound like the switch.

 

[Passages]

If the pump stops when you touch the rod on the switch, it s usually the switch. But you said you replaced it... one of mine does that sometimes but the switch is 15 years old

If you had a leak the pump would stop but cycle on and off. It really sound like the switch.

I bought and installed a new switch today. Not the switch because it's acting the same as the old switch.

 

[sixty]

If its adjustible, have you tried adjusting the spring on the switch? Also maybe sounds like the vacuum indictor is binding. Try spray woth teflon or silicone.

 

[Walter P]

Jim, It's haunted. For a small fee we can perform an exorcism after which you supply the drinks..lol

Seriously, It sounds like you did almost everything necessary but my guess is that there is still some
sort of leak, perhaps at the switch? Sorry I couldn't help.

Walt

 

[oceanjake]

That knurled knob can be adjusted to set the PSI at which the pump will turn off. I would just adjust it down a bit. As long as it still has enough pressure to clear the system you’ll be fine. If not the switch i’d Guess duckbills are deforming slightly

 

[Passages]

That knurled knob can be adjusted to set the PSI at which the pump will turn off. I would just adjust it down a bit. As long as it still has enough pressure to clear the system you’ll be fine. If not the switch i’d Guess duckbills are deforming slightly

Duckbills are all new. The counter guy at EMI in Ft Lauderdale said not to try to adjust the knob. It's factory set and Locktite in place. But you have me thinking...what if I shim the switch from the mounting posts just a tad? A thin gasket or washer would be all that's needed. This would effectively shut the pump off at a slightly lower vacuum but that's exactly what we want.

Stay tuned and I'll let you know how it goes.

 

[Pascal]

I bought and installed a new switch today. Not the switch because it's acting the same as the old switch.

New means Never Ever Worked

 

[JD5652]

Having replaced three of four on my boat over last three months... I have some experience with this.... and this problem exactly. One of my vacuflush did EXACTLY the same thing right after rebuilding by an knowledgeable marina tech. I watched him and he had an issue when reassembling the piping … the pump still ran continuously and would shut off at the most gentle touch on the vac switch. He adjusted the switch... still same... then he REALLY cranked on the PVC fittings... and it worked....

….for about a week.... then started doing same thing. I disassembled and found ONE of the new duck bills to be deformed. I wondered if it was due to overtightening of the fittings. I replaced that duck bill... reassembled the unit WITHOUT overtightening the fittings... it's been working correctly for last two months...

Not sure this is your issue... but it worked for me....

 

[Pascal]

That’s why I mentioned using liquid soap and not distorting the DB

 

[Passages]

SUCCESS!

Shimming the vacuum switch using 2 thin washers seems to have done the trick.

Plenty of "whooooosh" when the pedal is depressed and the pump runs for about 15 seconds to re-establish vacuum.

Now for the next project.