Quote:
Originally Posted by AZ RV'r
I had that same situation, red light on, motor never stops pumping, mine seemed like it was running at a slightly faster speed. I decided after talking with an RV tech here in Phoenix that several of my friends have used and recommended as good, honest, and knowledgeable ....to change out the pump.
This is what he said to me...
"Most of the time its NOT the duck bills. It takes me the same amount of time / money to change just the duck bills as changing the whole pump. If I change the duck bills, it usually doesn't fix it and now I have to charge you labor to go back and change the pump (separate trip charge)
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AZ RV'r, I know I posted in your thread too. I didn't quote you to argue or in anyway belittle your experience... I only quoted you, to offer an opposing opinion, to the OP...
I've used vacuflush toilets on 2 different boats over about a 20-23 year period...
The first boat was a single toilet system, with one toilet, one pump, and one vacuum tank. The second boat had two toilets, two pumps, and two vacuum tanks, that led to one large holding tank. I even used a Sealand pump for the overboard discharge on that boat.
I understand these marine/older systems are a little different from the RV systems. The marine system's components seem more robust to me, and a bit larger, but the concept and operation are extremely similar...
I installed and maintained both my systems... I lived aboard the boat with two heads for 14 years... I used the main stateroom head daily, and the guest head when guests were onboard or the main head needed maintenance..
Over those 25 years, I replaced one pump, rebuilt one pump, and replaced the duck bill valves about every 2-3 years on the first system, and about the same on the second boat head I used daily, less frequently on the guest head. I have never had to replace a failed vacuum switch on the vacuum tanks, but have replaced a toilet bowl seal about 4 times total for both systems.
In all the cases, the symptoms were the same as yours... Failure of the pump to shut off. The failure to shut off is due to the inability to build vacuum and/or have the vacuum shut off the pump. The possibilities are; bad/fouled/leaky toilet bowl seal, bad/fouled duckbill valves, bad pump/pump diaphragm, bad vacuum switch, or a leak in the system.
Note the sound of the pump... If it's running rapidly and without laboring, it's not building vacuum. If the vacuum switch were to fail, the pump will slow and start to labor as vacuum builds, but it won't shut off. It may even blow a fuse. The same symptom, laboring pump/possible blown fuse, will be present if the pump/diaphragm were jammed by debris or just a build up of crud over time...
It was MY experience that a constantly running pump, that wasn't laboring, was almost always the duck bill valves... Either a good flush of the system cleared them up if they were fouled, or the valves got warped, worn, and needed replacing. The same symptoms presented for a bad bowl seal, but far less frequent than the duckbill valves.
When clearing/replacing the seal/valves didn't work, I then looked for one of the other causes.. replacing the valves is good preventative maintenance, even if they turn out to not be the problem, this time...
I realize my experience isn't scientific proof, just anecdotal experience...
But at about $35 for 4 new duckbill valves versus over $300 for a new pump... I always checked/replaced the duck bill valves (and/or bowl seal) first... and about 75% of the time, duck bill valves fixed the issue for another several years...
Good luck with your repair...