Vacu flush question

brewster16

brewster16

Well-Known Member
Aug 9, 2009
1,452
Long Beach Island, N.J.
Boat Info
'07 44 Sundancer
Engines
Twin Cummins QSC 8.3
Does anyone know specifically if after changing all 4 duck bill valves and the bellows pump if the system needs to be primed?

After carefully doing all the work above the pump motor is STILL running continuously. Light is still red!
 
1. Can you take the cover off of your pressure switch and tap down on the diaphragm and get it to stop?
2. Did you use silicone grease on all the O Rings and duckbill bases?
 
The toilet bowl is full of water but when I step on the pedal vacu flush won’t suck it down. Light is red and pump is running. My thoughts now are I either need to prime the pump (some how) or use a plunger to clear a clog in sanitation line… thoughts??
 
Carter I will certainly try your diaphragm switch suggestion. Yes, silicone grease on all components. I have a new switch ready to go just in case. But assuming it is the switch would that account for no vacuum at all?
 
The "pump" is a positive displacement pump so it generally doesn't need priming. As it generates vacuum, it empties the line of liquid on the upstream side of the pump.

Are you sure that you put the duck bills in the correct orientation? Fat side pointing upstream/slit pointing dowstream.

Jaybeaux
 
Or could have a blockage in the line between the toilet and the vacuum generator (large turd, toilet paper, diaper, dishtowel, etc.)
 
We’ll gentlemen…..I am going to focus on the switch because I don’t have a plunger on board. So, I’ll be back…..
 
If you have a clog, vacuum should still build up - it just won't be able to suck the clog down. I had one doing what yours is doing, I replaced the switch, it didn't help. I took it all apart and put it back together and its worked perfectly for 2 years now...
 
Four Suns said:
Or could have a blockage in the line between the toilet and the vacuum generator (large turd, toilet paper, diaper, dishtowel, etc.)
Click to expand...
I disagree with this scenario. If there is a blockage between the toilet and the generator (assuming the blockage is 100% complete) eventually, the bellows pump should generate enough vacuum to satisfy the vacuum switch and shut the pump off. @brewster16 mentioned that the bowl is full of water (not leaking) and when he flushes, there is zero vacuum, yet the vacuum pump never shuts off. I'm leaning toward a vacuum leak somewhere around the vacuum generator system.

Jaybeaux
 
Mine was at the fitting where the hose from the toilet connects to the input of the vacuum generator. That would also account for the stink in the engine room. I'll bet your level indicators are stuck at reading full, or you really have a full tank, which would also account for the stink if there is the slightest leak in the tank itself. A test for that would be to tap on the fitting on the top of the tank where 3 wires come out. see if your lights don't change.
If you can get some kind of smoke generator around the fittings, that might tell a story as well.
Vacu flush diagram.jpg
 
brewster16 said:
Carter I will certainly try your diaphragm switch suggestion. Yes, silicone grease on all components. I have a new switch ready to go just in case. But assuming it is the switch would that account for no vacuum at all?
Click to expand...

Definitely not the switch, that only turns the system "off" when vacuum is reached. And you would get suction at the head if it was just a malfunctioning switch. Like other posters said, it's likely at the vacuum pump/accumulator, or downstream of the pump. If it was 'more-or-less' working before you changed the ducks, I am betting on either a backwards install (not hard to do) or a fitting/gasket was disturbed in the process.... also make sure the fittings around the ducks are all tightened (but don't overtighten ... basically use a wrench for a quarter-turn past hand tight) and the hoses are on far enough and tightly duo-clamped.
 
370Dancer said:
Mine was at the fitting where the hose from the toilet connects to the input of the vacuum generator. That would also account for the stink in the engine room. I'll bet your level indicators are stuck at reading full, or you really have a full tank, which would also account for the stink if there is the slightest leak in the tank itself. A test for that would be to tap on the fitting on the top of the tank where 3 wires come out. see if your lights don't change.
If you can get some kind of smoke generator around the fittings, that might tell a story as well.View attachment 108642
Click to expand...
HEY! That's MY PICTURE!
 
A crack in the bellows of the pump would cause this issue. Also, there is an o-ring for the bellows that I misplaced on putting everything back, and this prevented any suction from building up. Once I put everything back in correctly, then I un-hooked the toilet hose, covered the hole, and suction built up and pump stopped and stayed off for 2 minutes. Then, I connected the hose, and it would run about every 30 seconds. Finally, replaced the little bolt in flush mechanism, and that fixed everything….
 
Island Time Buffalo said:
Definitely not the switch, that only turns the system "off" when vacuum is reached. And you would get suction at the head if it was just a malfunctioning switch. Like other posters said, it's likely at the vacuum pump/accumulator, or downstream of the pump. If it was 'more-or-less' working before you changed the ducks, I am betting on either a backwards install (not hard to do) or a fitting/gasket was disturbed in the process.... also make sure the fittings around the ducks are all tightened (but don't overtighten ... basically use a wrench for a quarter-turn past hand tight) and the hoses are on far enough and tightly duo-clamped.
Click to expand...
Will do! I’m back in the bilge tomorrow morning…..
 
I thought FOR SURE this was the issue….but it’s something else. (Don’t crush your duckbill seals by over tightening!
6BECEFFD-2C51-4134-9F80-FFB9B33A71F6.jpeg
 
Todd320 said:
A crack in the bellows of the pump would cause this issue. Also, there is an o-ring for the bellows that I misplaced on putting everything back, and this prevented any suction from building up. Once I put everything back in correctly, then I un-hooked the toilet hose, covered the hole, and suction built up and pump stopped and stayed off for 2 minutes. Then, I connected the hose, and it would run about every 30 seconds. Finally, replaced the little bolt in flush mechanism, and that fixed everything….
Click to expand...
What little bolt in the flush mechanism are you talking about Todd? Have a picture or diagram of it?
 
You can take the inlet hose off the inlet fitting on the tank and block it off to see if the pump generates vacuum and shuts off. If it does, work upstream. If it doesn’t, it’s in your pump somewhere

had a similar situation and found it to be one of the pvc fittings. Had to be methodical with troubleshooting one thing at a time
 
You must log in or register to reply here.

Forum statistics

Threads
113,144
Messages
1,427,238
Members
61,057
Latest member
DrBones!
Back
Top