Vacuum toilet runs for a long time after flushing

Beech2000

Active Member
Jul 11, 2015
242
NW Georgia USA
Boat Info
1990 Sundancer 350
Engines
2020 454 gen VI
Hurth V-Drive's
7.1 KW Kohler 5ECD
Crappy situation. I have the vacuum potty system in my 90 350. After flushes, vacuum pump runs for 6 minuets or longer before slowing and or sealing. Is this normal?
 
Assuming you have the traditional vacuflush setup?

Seems longer than normal, but also depends on how long you hold the flush lever open and/or number of flushes per use.

Problems that I have ran into all involve some type of leak, where vacuum doesn’t hold or takes longer to build the vacuum (longer pump times like you’ve described).

Once the pump shuts off - how long before it kicks back on - assuming no one flushes? Meaning - how long does the vacuum hold? This will help tell us if there is a leak somewhere which may cause longer pump times.

I’ve read (and experienced) that it helps to side step your foot off the toilet flush petal, allowing it to snap back closed helping to reseal the bowl. Otherwise sometimes the pump runs to build vacuum and you can hear it sucking in air from the bottom part of the bowl. In this case though, the pump runs forever unless your lucky enough where the bowl finally seals after a minute or two.

One final note - when you say it runs slower - that seems strange. It should be a single speed motor and should always run with the same clunk-clunk-clunk pattern - no slowing. Do you have a fully charged battery? Perhaps the motor isnt running full speed (longer time to build vacuum) and the battery is giving out towards the end of the pump cycle causing it to run slower?
 
With new duck bill valves in both our heads they run for 90 to 120 seconds. The forward one runs the longest. It has a newer pump. I have not changed the diaphragms in either of then or the motors. Last year the overboard one did not work at the start of the season but did after many tries. I changed the duck bill valves on it this spring they were worn to the point they were not closed.
 
Mine takes about 10 - 15 seconds, so 6 minutes seems way out of whack. If it maintains the seal after the pump shuts off, that would seem to point to a weak or clogged pump. If it cycles back on at some point for no damn good reason, I'd assume a vacuum leak somewhere.
 
I could even be the little vacuum switch (has the 2 red wires going to it) that is on top of the tank.

I think there's a way to trouble shoot somehow.

Picture just for reference.

56_85_dometic_vg4_9108554947_35685_13.jpg
 
I think ours runs so long as the runs to the pumps are probably 20+ feet. There is no evidence of leaking and they do not cycle when not in use. Before I replaced the duck bill valves they would cycle about ever 2 hours.
 
When I arrived today at the dock the toilet was sealed and pump was not running. Cup of water in bowl. Flushed it once and experienced a strong vacuum followed by the pump which ran for 3 minuets. Last 5 seconds were slow. I don't think its leaking at present but do suspect flow or restriction.
 
I thought my 45 seconds was a long cycle time but I guess not. Ay 6 minutes something is not right. I would suspect the diaphragm. If it were duckbills the system would not hold vacuum and cycle between flushes.
 
I finally got mine working by tracking down some small leaks and replacing the pump altogether, but still mounted an illuminated switch in the head.

The on demand pump is fine and I don’t worry about it anymore.
 
2808670-R1-015-6.jpg
I turned our VacuFlush on for the first time yesterday, after having serviced it last fall. It ran for maybe 30 seconds and shut off. Flushed it again and let some water run into the bowl and it shut off again in 30 seconds. The boat is 2004 so the head is the same. These are very reliable units if you use them and maintain them per the instruction manual. Ours does not cycle between uses and goes all night with no cycling.
 
Changed ours out at beginning of last season. It was doing similar to yours. It started taking longer and longer to build the vacuum and shut off until eventually it would not build up a vacuum at all and just kept running. Removed pump assembly, disassembled, duckbills obviously toast. Cleaned unit real good - there will be areas of accumulation - replaced the 4 - 2" duckbills and re assembled. Now works as its supposed to. When flushing vacuum is strong and pump only runs 20 seconds.
 
Beech2000,
Assuming you have the same VacuFlush system as I do on my ‘88 sedan bridge, I went through the same issue when I first purchased my boat.
After replacing duck bill valves, bellows, and all of the seals on the pump it self, I still had the same issue. The pump would run and run and not shut off. But when I flushed the toilet there was obvious vacuum within the system, forcing the water into the holding tank. A leak wasn’t my issue.
There is a vacuum switch on the end of the accumulator tank. My part number for the accumulator tank 7291. I read that it should be replaced every five years or so. There is a date written on the side of the switch. Mine was the original switch I believe dating to 1988.
It’s an expensive part, little under 200 bucks. But it’s easy to replace and fix your issue. The switch unit screws onto the side of accumulator tank. Attach wires as they were on the old switch and your good to go.
The switch comes factory set. You can try to adjust your switch your self by rotating the screw on top of the spring. I didn’t have any luck.
I use Marinesan.com.
Link to accumulator tank.
https://www.marinesan.com/Accumulator-Tank-s/181.htm
Link for the switch
http://www.marinesan.com/7291_Vacuum_Switch_p/385318032.htm

Hope this helps. If you have a totally different system, disregard the links and try replacing the switch for your system.

Any questions or picture you and message me directly.

-TP
 
Assuming That it holds vacuum i would change the vacuum switch they have a life of about 7 years i'm told
 
Response to an old thread. As OP thought I'd report the ultimate fix.
Removed and cleaned aft vac u-flush components with Tide detergent and water. (Tanks included).
Replaced 4 duck bill valves
Replace Diaphragm Bellows and seals
Replaced Tank Switch
Removed dump maceration pump. (No longer functional) as we are fresh water
Replaced 1.5" hoses around the tank, diaphragm, pump out. Only hose not changed is the long run to commode.
Replaced Tank switch
Removed toilet and replaced seals

Yup old boat new vacu-flush and now incredibly perfect. 2 seconds no mater who uses. Done!
 
Glad it worked, mine runs about a minute, already changed the duckbills. In the spring I plan on changing the bellows.... if that doesn’t do it, I will do the vacuum switch.... thanks for this thread and there follow up!
Response to an old thread. As OP thought I'd report the ultimate fix.
Removed and cleaned aft vac u-flush components with Tide detergent and water. (Tanks included).
Replaced 4 duck bill valves
Replace Diaphragm Bellows and seals
Replaced Tank Switch
Removed dump maceration pump. (No longer functional) as we are fresh water
Replaced 1.5" hoses around the tank, diaphragm, pump out. Only hose not changed is the long run to commode.
Replaced Tank switch
Removed toilet and replaced seals

Yup old boat new vacu-flush and now incredibly perfect. 2 seconds no mater who uses. Done!
 
Response to an old thread. As OP thought I'd report the ultimate fix.
Removed and cleaned aft vac u-flush components with Tide detergent and water. (Tanks included).
Replaced 4 duck bill valves
Replace Diaphragm Bellows and seals
Replaced Tank Switch
Removed dump maceration pump. (No longer functional) as we are fresh water
Replaced 1.5" hoses around the tank, diaphragm, pump out. Only hose not changed is the long run to commode.
Replaced Tank switch
Removed toilet and replaced seals

Yup old boat new vacu-flush and now incredibly perfect. 2 seconds no mater who uses. Done!
This is the part of boating no one tells you about when your buying one ! lol lol
 
Glad it worked, mine runs about a minute, already changed the duckbills. In the spring I plan on changing the bellows.... if that doesn’t do it, I will do the vacuum switch.... thanks for this thread and there follow up!
Did you ever solve? I changed duck bills but it runs for about 20 seconds every hour. I sprayed all fittings with soap water and no issues. Toilet holds water so I guess it is the bellow next?
 
Did you ever solve? I changed duck bills but it runs for about 20 seconds every hour. I sprayed all fittings with soap water and no issues. Toilet holds water so I guess it is the bellow next?
Just changed the bellows yesterday, when I initially put it back together, wouldn’t shut off at all, took it all apart and lathered the o rings and areas that need to seal with petroleum jelly. That solved my issue, or at least made it better. Mine now runs about 45 seconds. Here is the thread I started
http://www.clubsearay.com/index.php?threads/replace-bellows-in-my-2000-380-da.106447/
 

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