Vacuflush runs every 10 minutes

So the bowl is holding water so it appears good. I’ve changed the duck bills all 4. I’ve changed the 2 o-rings in the bellows housing. It still runs every 5-10 minutes or so. I can hear it internally bleeding by at the main pump but can’t find it. Any ideas on what’s next? Ordered a new bellows kit to try. But if that was bad I’d think it wouldn’t build vacuum at all.

I would try getting a spray bottle with water and spraying areas around where you think you hear the vacuum bleeding. When the sound changes because of the water you at least know the general area.
You may have a crack in the poly tank (hopefully not)

Get a spray bottle of water and lightly spray the connections and fittings you might be able to see the water dissipate quickly and see the leak. Also make sure everything is double clamped. The bellows can get cracks on the folds weaken before they fully crack and leak through osmosis.

Clamps tight? None of the plastic housing is cracked? of you can hear it hissing, wondering if you can spray some Soapy water around areas to see where it is bubbling?

See what I can come up with. I felt around all the connections everything tight. And didn’t notice and change in sound when I was feeling around. Probably try the bellows next if that isn’t it maybe I got bad duck bills possibly. The OME ones were out of stock so these were knock offs. But they looked good.

Did you lube the duckbills? when I installed the new duckbills, it still was cycling, the second try I put a bunch of silicone grease (like vasaline) on mine. Which fixed it, been a couple years since and no issues

also, make sure you put plenty of lube on the orings you replaced

If you take the duckbills back out to lube them, examine the rims on them to be sure they were not crushed from over tightening.

A few weeks ago someone mentioned the way to isolate the problem part of the system is by disconnecting the sanitation hose from the vacuum tank then seal the tank opening with Saran Wrap. If vacuum holds (doesn't cycle) the system is not leaking from any of the "downstream" components (duckbills, O rings, bellows, switch. Although I have yet to do this, it makes a lot of sense!

Best tool ever... You can narrow down exactly where your leak is.

https://marinesan.com/dometic-vacuu...MIxrbuycWq-AIVMQJ9Ch2lHQtREAQYASABEgK6Y_D_BwE

Too Young said:

So the bowl is holding water so it appears good. I’ve changed the duck bills all 4. I’ve changed the 2 o-rings in the bellows housing. It still runs every 5-10 minutes or so. I can hear it internally bleeding by at the main pump but can’t find it. Any ideas on what’s next? Ordered a new bellows kit to try. But if that was bad I’d think it wouldn’t build vacuum at all.

Click to expand...

I just went through this with my aft head vacuum generator, which is mounted on my waste tank.... you all will love this!

Initially, the pump would turn on if I bumped into the tank when I was doing work in the engine room. Having owned the boat for less than a year, I recently replaced the duck bills and bellows on my forward heads vac generator located on the other side of the engine room, so I figured the duck bills on this one were due for a change.

Once completed, the pump was sucking air and would not shut off, so I decided to change the bellows. Once completed the pump would still not shut off. I decided to replace the pump gasket, which is the circular flat one between the tank and the pump housing and when I did, found that the upper duck bill valve that seals on top of the removable tank collar above the lower duck bill was deformed. This probably happened when I reassembled it after initially replacing the duck bills. I swapped it out with one of the two new ones that led to the waste tank, gooped them all up with the thick grease I purchased from the Dometic dealer and that solved the constant running problem, but the unit would still turn on when I bumped the waste tank, so I changed the pressure switch, which was on it's way out and the reason why the pump would turn on when bumped.

After replacing the flanges, seals, water valves, check valves on both bowls and the parts on both vac generators to the tune of about $1,000 in material, I'm hoping there's nothing left to break!

I suggest you disassemble the unit, replace the bellows, check for damaged o-rings/valves, goop everything up (including the seal on the bottom of the pressure switch), reassemble and tighten it all up.

Spending a $100 bucks on the right tool will tell you what side your problem is on in 30 mins.
1. Disconnect inlet on pump box insert gauge, power unit on and wait for pressure to build, wait and see it does not cycle. If that passes move to step 2 If it fails your issue is in the vacuflush unit.
2. Reconnect inlet hose from the head. Disconnect the hose to the toilet and install the gauge into the hose. Power up and again test for holding vacuum. If it fails then your hose is bad or your connections leak. If it passes and does not cycle then your issue is the toilet side.