Dometic pressure problems

I am sorry but I am lazy and can’t search thru all the toilet issues on this site.

for some reason since storage both toilets get pressure …green light but after 15 to 20 minutes both start pumping again to get pressure…lots of water in bowl…. And the cycle repeats. Is this duck bills?

I have run tons of water thru them and same result… I just can’t believe both heads have same problem

Not saying this is your problem although we had same problem at end of last season. I am somewhat of an over achiever when making repairs as I change out stuff since I have it apart anyway. As I investigated where it could be coming from I also decided to just replace all the seals, etc in the toilet since it would be apart. Ours would hold water as well, but pump would cycle every 20 min or so. In trouble shooting, I first removed the intake hose from my vacuflush system at a tank and occluded it with a flared rigid plastic cup (it fit nicely in the hose and acted as a cork) and then turn the system on to see if we still had a leak. Held fast for about 4 hours with no issues. This ruled out the vacuflush system and told me my issue was the toilet or hose running from the toilet to the tank. This is when I decided to rebuild the toilet. When removing the toilet I found that one of the 4 mounting plate bolts was not sealed (from fluids) properly when installed like the other 3 were and had rusted (yes it was a stainless screw) to the point it was not holding the seal down. This is where my leak was. Cleaned up everything and reassembled with all new seals and a new mount. All good and should be trouble free with proper maintenance for several years.

Seems like the vacuum pumps kick back on? But your not loosing ajy water in the bowl? If so - I would vote for duckbills as well. Sitting in storage everything dries out. It takes a day (of regular use) for ours to behave normally again.

The water will help lubricate the valves so they cab seal better again. There is a chance something dried on the valves which is preventing a good seal. Either time (water and usage) will solve, or rip/clean/replace may ne in order.

When you did winter layup - do you winterize the head/tank - which would include flushing just liquid / antifreeze through - helping to clean the system out?

You need to drop a couple dueces in there and run those pumps through their paces, @Blueone

Blueone said:

I am sorry but I am lazy and can’t search thru all the toilet issues on this site.

for some reason since storage both toilets get pressure …green light but after 15 to 20 minutes both start pumping again to get pressure…lots of water in bowl…. And the cycle repeats. Is this duck bills?

I have run tons of water thru them and same result… I just can’t believe both heads have same problem

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I believe you only have one vacuum generator and it could be the pressure switch on the generator or it could also be the duck bills. Run some very HOT water through the system and try that a few times. If the cycle times extends then it could be the bills, if not the pressure switch. Any chance of putting a vacuum gauge on this some how? That would tell you right away.

All of the statements above are very true. To trouble shoot ALL of them, do the test I mentioned. Remove the intake hose, block off the intake to the tank and see if it continues to cycle. If it does not, the leak is before that inlet. It is a quick troubleshooting procedure that isolates the vacuflush from the toilet. If it does, start with replacing the duck bills and pump diaphragm. It is a bit of a nasty job, but elbow length rubber gloves and a little vapor rub under the nose and you can get er done. A few years ago when I had a leak, I took mine out and pressure washed all the parts (other than electronic pieces). Put in new duck bills a pump diaphragm and all good. They also make a test kit which I have that will actually tell where the problem is. I think I got it off the Dometic site.

There are actually 2-vacuum generators-one for each system. Another thing that is difficult to find is the brass shaft that connects the pedal to the 1/2 ball. You have to cut everything off, get things as quiet as possible, put your ear down around the pedal and see if you can hear a very faint hiss. On that shaft there is an O-ring that seals it off. If that gets dried out or cracked a little, it creates a vacuum leak. I installed new bellow, new bowl seal, new duck bills, and walked away only to have the generator kick on every 30 mins or so. Had my wife listen and she could hear the "hiss." When got down on my knees closer to it, I could hear it as well. Replaced the shaft with the O-ring and all 100% good now. This was the head in the MSR. With the duck bills, O-rings or anything rubber, use plenty of silicone grease.

Bennett