Dometic VacuFlush head, my first dive into troubleshooting

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GrandWood

Senior Member
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Jul 16, 2022
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Hello all, boat noob here and the vacuum pump is now running continuously. Last night I heard a noise in the head and there was no water in the bowl, and you could see a slight sucking around the ball in the bottom. Put a bunch of water in the bowl and flushed. Holds water in the bowl but the pump now runs continuously. So seems it’s not holding vacuum. Been working well for 2 months now, but had noticed the pump seemed to run a bit longer recently.

Dont know spit about the system other then what I have been reading this am. Would be great to get a few pointers on how to attack the problem, as I’m scared of dumping poop all over the place. If I flush lots of water through it, that should clean out the lines and such so I don’t make a mess right?

The boat has been neglected as far as continuous maintenance on just about everything. Thinking that there might be a kit from the company to replace all the seals, duckbills and such to insure it’s good to go instead of just replacing what might be going/gone bad.

The fear of dumping poop everywhere has me hesitant to even look at anything, so any input and tips would be greatly appreciated, I want to be able to maintain the system myself, and this will be my OJT first time out, thanks.

I’m going to send my email to Peggy for her 101 info on the system
 
In preparation to working on the system I flushed three bowls of soapy water down and alls good now, vacuum pump takes about 20-30 secs to build vacuum and shuts off. Bowl holds water, so guess there was a slight clog in the duckbills?
 
Hope you turned the pump off.
If the bowl seal is leaking, open the bowl valve all the way and wipe the inside of the seal with a wet rag to make sure it's clean. It's also important to not let the valve close slowly. From wide open, simply remove your foot from the pedal and let it snap shut quickly.

Ted
 
GrandWood said:
In preparation to working on the system I flushed three bowls of soapy water down and alls good now, vacuum pump takes about 20-30 secs to build vacuum and shuts off. Bowl holds water, so guess there was a slight clog in the duckbills?
Click to expand...
As a matter of due diligence, I would replace the four duckbill’s in the vacuum generator. These are a replacement item and can be sourced at most any marine store. Do not buy the cheap ones on Amazon.
 
O C Diver said:
Hope you turned the pump off.
If the bowl seal is leaking, open the bowl valve all the way and wipe the inside of the seal with a wet rag to make sure it's clean. It's also important to not let the valve close slowly. From wide open, simply remove your foot from the pedal and let it snap shut quickly.

Ted
Click to expand...
Thank you sir for checking in, much appreciated
 
OC Diver is right. Also, I regularly use a toilet brush to keep the bowl seal clean. Then next problem could be warped duckbill valves. I replaced the valves in the aft Vac Head in 2018. Just now they are starting to leak a little so the vac pump will go off early in the morning hours unless I flushed in the middle of the night. Another item would be an air leak in one of the connections to the tank. Some Vac toilets have a base seal which can leak and harder to get to. I had that problem, replaced it. Still a problem, replaced it again. Still had the problem. took out the base and put in a taller one without that seal and that fixed it. Last there could be a leak in the bellows. When I had smells in that area I replaced mine but that was not the problem, it was permeated hose.
 
A pump that has been running longer and longer after a flush and finally won't shut off at all is almost certain to be a failed vacuum tank switch. This will not cause the pump to cycle for no reason between flushes...an air leak in the plumbing and/or worn duckbills causes that. The vac tank switch has a sensor in it that turns the pump on when there's a loss of vacuum (a flush) and turns it off when the prescribed amount of vacuum has been reached. As the diaphragm begins to wear out, it develops pin holes. As they get larger, the pump runs longer and longer until it no longer turns off . That switch should not be adjusted, should be replaced. Brace yourself for sticker shock...Dometic is, as we say in the south, very proud of their replacement parts.
Someone on this forum posted recently that he'd been able to successfully replace Just the diaphragm. Hopefully he'll chime in here.

--Peggie
 
HeadMistress said:
A pump that has been running longer and longer after a flush and finally won't shut off at all is almost certain to be a failed vacuum tank switch. This will not cause the pump to cycle for no reason between flushes...an air leak in the plumbing and/or worn duckbills causes that. The vac tank switch has a sensor in it that turns the pump on when there's a loss of vacuum (a flush) and turns it off when the prescribed amount of vacuum has been reached. As the diaphragm begins to wear out, it develops pin holes. As they get larger, the pump runs longer and longer until it no longer turns off . That switch should not be adjusted, should be replaced. Brace yourself for sticker shock...Dometic is, as we say in the south, very proud of their replacement parts.
Someone on this forum posted recently that he'd been able to successfully replace Just the diaphragm. Hopefully he'll chime in here.

--Peggie
Click to expand...
Thank you Peggie, much appreciated, as I said above, in preparation to taking pump off and such I ran three bowls of soapy water through the system and now the pump turns off within 20/30 secs, seems to flush fine. Will definitly keep a close eye on it, as the problem may well return. I have been adding 1/2 gallon of fresh water each flush, as had been said would help with a VacuFlush head since we purchased the boat.
 
I don't think you need to fill up your holding tank with that much water, but I do recommend following each flush with a quart to rinse behind the flush because the flush water flow is too wimpy to fill the hoses, much less rinse out the vac tank, duckbills and the pump. And btw soapy water needs to be rinsed out too.

Peggie
 
Once again thank you, and yes sticker shock on the switch. Went out to lazzarette and found location of the switch and there’s no cover on it. Rained all night, switch is dry but maybe moisture may have had something to do with it. Think I will order a switch for backup as we plan on being on the hook most of the summer, and duckbills as there reasonably priced. Will find something to cover the switch as well.
 
Never make the mistake of buying VF parts from 3rd party vendors...they're knockoffs that not only may not fit, but can actually do damage. Dometic will only allow genuine VF parts and equipment to be sold by their authorized retailers/service centers.
 
HeadMistress said:
Never make the mistake of buying VF parts from 3rd party vendors...they're knockoffs that not only may not fit, but can actually do damage. Dometic will only allow genuine VF parts and equipment to be sold by their authorized retailers/service centers.
Click to expand...
Looking at Environmental Marine for the parts
 
FYI, if you are so inclined to shop at Amazon, Dometic has a storefront, so you can get genuine Vacuflush parts there, but as Peggy says, be wary of aftermarket parts.

 
I have had always made it a practice to lift the pedal briefly after each flush to be sure the ball is seated all the way. It adds a little water to the bowl, but not too much as long as you don’t hold it for a long time.
In the decades that I’ve run vacuflush systems I’ve never had a pressure switch seal go bad. Just lucky I guess.
 
HeadMistress said:
Never make the mistake of buying VF parts from 3rd party vendors...they're knockoffs that not only may not fit, but can actually do damage. Dometic will only allow genuine VF parts and equipment to be sold by their authorized retailers/service centers.
Click to expand...
Absolutely agree. Bought duckbills, o-ring and bellows from Amazon, they came in Dometic packages but would not work. Bought all new from Dometic dealer and now all works perfectly.
 
Marine San and Environmental Marine are both good vendors. Both have helpful employees and good diagrams on their websites. I have had several vacuflush systems over the years. I would say the most common vacuum loss points are the duckbill valves, the seal between the bowl and the clamshell and the o-ring that seals the flush pedal shaft. Less common are a loose hose connection in the system. I would start with your duckbills as they are your most likely culprit. Having said that if you bowl is dry and you hear air sucking the seal at the clamshell your first route.
 
As you gain experience maintaining the system it will become easier. Lots of good advice above on what to look for. Eventually you may run up against a vacuum loss you can't easily track down. Then you'll want a vacuum tester. The official Dometic tester or a roll your own.
 
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