Strange vacuflush issue - pump keeps running despite replacing almost everything

K

k9medic

Active Member
Mar 27, 2013
597
Florida
Boat Info
1998 420 Aft Cabin
Engines
twin 3116 CATs
Here is a new one for the group -

Vacuflush pump keeps running. Replaced all of the duck bills. Replaced toilet bowl gasket.
Pulled hose off of pump container and can feel a solid vacuum. Pulled hose off of pump and it holds suction on my hand. Replaced pressure switch. Bowl holds water. Put some soap in the bowl and flushed it. No bubbles or leakage around the tank.

The only thing I can think of is an issue with the bellows but there is no effluent or signs of leakage.

Thoughts?
 
I can compress the spring and the switch turns the pump off.
 
Disconnect the hose from the inlet at the vac tank and plug the fitting (I wasn't sure if you left your hand on there long enough for that?). This eliminates everything upstream (towards the toilet). Does the pump now turn off? "Yes" or "no" will tell you which direction to look in. You may also want to check the inlet elbow and seal - maybe even removing that and covering the "hole" in the tank with something stiff and some tape. If it still runs... with it still plugged, let it run for a minute and then kill the power. Listen for leaks. Other suspect items would be the diptube and seal, along with the pressure switch seal... but I assume you used a new seal when you replaced the switch.

It's also possible to have clog in the discharge side that would sometimes cause this.
 
I removed the pressure switch (switch still connected) and put my hand over the opening. There was vacuum. This was to see if there was a clog up in that area.

I removed the pump from the tank and put my hand over the opening (that would normally go into the tank) and there was vacuum

I removed the hose that comes from the toilet to the tank and put my hand over the tank inlet. There was vacuum. Pump did not turn off.

New pressure switch had new o rings and a clamp. All of those were tight. Tried this with power on and off too.
 
k9medic said:
I removed the pressure switch (switch still connected) and put my hand over the opening. There was vacuum. This was to see if there was a clog up in that area.

I removed the pump from the tank and put my hand over the opening (that would normally go into the tank) and there was vacuum

I removed the hose that comes from the toilet to the tank and put my hand over the tank inlet. There was vacuum. Pump did not turn off.

New pressure switch had new o rings and a clamp. All of those were tight. Tried this with power on and off too.
Click to expand...
How long does it take till the pump comes back on The fact that the pump doesn't shut down you could have a bad Vacuum switch i know you replaced it but it might be a bad one!
 
If I manually manipulate the vacuum pump switch (both the old and the new) the pump will shut off.
 
k9medic said:
If I manually manipulate the vacuum pump switch (both the old and the new) the pump will shut off.
Click to expand...
So your pulling a Vacuum it just won't shut off its got to be the Switch
 
Try turning the system off after a minute of pumping after a flush. Wait for a half hour or so, then flush without turning the system back on. If you still have vacuum to flush, there is no leak anywhere in your system and the vacuum switch is not doing it's job to cut power.
 
I'll be back down on the boat tomorrow so I'll try that.

@Express 390, that's what I was thinking too which is why I bought a new pressure switch. It just doesn't make sense though that there would not be enough pressure to pull the plunger to open the contact.
 
Can you adjust the pressure switch? I thought I remember a roller on it to adjust pressure.
 
They seal the pressure switch, so you cannot adjust it. Did you use any silicone grease on the orings and duckbills when you reassembled? I had to do one of mine twice and the silicone grease finally sealed it all up...
 
I just went through this.....same issue as you. Turns out that I had used a wrench and overtightened the large white plastic nut that closes over the duck bill valves. Totally crushed the New duck bill valve rims creating a leak and allowing for air to get by. I too had vacuum against my hand but not enough to trigger the switch. I re-replaced the duck bill valves, put a healthy amount of silicone lubricant around the rims and hand tightened the big nut. Green light....Success!
 
I replaced both my pressure switches last summer and they both had a screw type adjustment on top of the spring. I struggled with getting mine to shut off as well and turned out it just needed 1/4 turn and all was well.
 
k9medic said:
I'll be back down on the boat tomorrow so I'll try that.

@Express 390, that's what I was thinking too which is why I bought a new pressure switch. It just doesn't make sense though that there would not be enough pressure to pull the plunger to open the contact.
Click to expand...
The vacuum switch has a Diaphragm witch could have a leak in it, And just enough to stop the switch from tripping ! And the switch has 2 " nylon threads that you have to watch you don't cross thread on the install. Good luck i hope that does it! Les
 
k9medic said:
Here is a new one for the group -

Vacuflush pump keeps running. Replaced all of the duck bills. Replaced toilet bowl gasket.
Pulled hose off of pump container and can feel a solid vacuum. Pulled hose off of pump and it holds suction on my hand. Replaced pressure switch. Bowl holds water. Put some soap in the bowl and flushed it. No bubbles or leakage around the tank.

The only thing I can think of is an issue with the bellows but there is no effluent or signs of leakage.

Thoughts?
Click to expand...
Double check the hose. You have a 22 year old boat and those lines should be replace @ every 7 years. Where there is a bend in the hose, check for air leaks.
 
+1 on the replacement for hoses!
 
Got to the boat on Friday and let the pump run for 8 minutes and then turned it off manually. 10 minutes later, attempted to flush with no luck (or vacuum.)
 
Mine turned out to be a slow leak at the hose inlet to the vacuum generator tank. The original tank has a molded in nipple as part of the tank. over tightening the hose clamp on the 1.5" hose was collapsing the nipple just enough to allow a slow leak. The newer tanks just have a hole, and a gasket the you insert, and then a right angle fitting for the hose. Near as I can tell, you just push it in. I contacted Dometic support to inquire what size hole is needed, so I could cut the nipple off of my tank and buy the kit with the gasket and elbow, but alas, Dometic did not find me worthy enough to answer. Or, perhaps they want me to purchase a new vacuum generator at 1,100.00.
new inlet with grommet.PNG
 
370Dancer said:
Mine turned out to be a slow leak at the hose inlet to the vacuum generator tank. The original tank has a molded in nipple as part of the tank. over tightening the hose clamp on the 1.5" hose was collapsing the nipple just enough to allow a slow leak. The newer tanks just have a hole, and a gasket the you insert, and then a right angle fitting for the hose. Near as I can tell, you just push it in. I contacted Dometic support to inquire what size hole is needed, so I could cut the nipple off of my tank and buy the kit with the gasket and elbow, but alas, Dometic did not find me worthy enough to answer. Or, perhaps they want me to purchase a new vacuum generator at 1,100.00.
View attachment 91684
Click to expand...

Try to call Marine Sanitation (marinesan.com). I have had them answer a lot of questions, and perhaps they can tell you the size of that donut...
 
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