I have an '00 396 that the vacu-flush pump runs every 5 minutes. Water never leaks from bowl. I cannot find any markings on the pump to get the model number. I've tightened up all the clamps. I don't believe it is the switch. Any clues? Ross
It is probably the duct bills in the ends of the sealand pump. They should be changed periodically. I usually do them every 3 years. You need 2 packages of 2, so 4 total. Basically make sure there is no vaccuum pressure in the system, and it also helps to flush water down the toilet a couple flushes first, then shutoff your freshwater pump and drain the system, then flush the remaining water down the bowl let the pump build vaccuum again, shut the sealand pump breaker off and hold the foot switch down until all the vaccuum is gone. Next take the hose clamps off of the hoses on the pump, heat the hose well with a heat gun (if it's the white sanitation hose) and pull it off, unscrew the ends and the duct bills should be in the ends, install new ones in the same order they came apart and put everything back together.
The only thing I would add is that when installing new duck bills I usually out a bit of liquid soap on the DB flanges and scrape any mineral deposit so they don't get twisted when you screw the fittings back on. Indeed duck bills need to be replaced, I usulaly get at least 5 years but you could also check for vaccum leak at the base of the headl deoending on the specific model, they may have a fairly soft seal under the base. Turn off any noise on th board including nearby AIrCons and listen carefully for a tell tale hissing sound around the base. If the DBs haven't been done in years, they likely need to be replaced,
Usually, the seland hose fittings are not barbed, loosen the hose and it comes off. At other times, loosen the clamps and you can still rotate the fittings to service the DB's and not pull the hose off if it is barbed. Turn the water off and release pressure before servicing. Just yesterday we replaced a frozen vacuum switch assembly. I backed off the thumb wheel, the spring rattled loose and I could not move the inter rod with a hammer. If it never shuts off, look over the switch assembly. Keep ventilation high. Have a fresh air fan blowing on you. Yep, you're in da Poo zone and you're going to need air.
I like to use super-lube grease on them. I also will put a set of gloves on and grease the bowl seal with it also.
Unfortunately the duck bills did not fix the problem. The pressure switch seems to be operating as it should. It seems like it would have to be an air leak somewhere. There is no odor, Any clues what the next step should be? I appreciate your help with this.
Maybe a good time to "call the man", and then watch what he does for next time. P.S. did you scrape and lubricate as Pascal suggested? Maybe do it again. I've found that with almost any job I try for the first time I mess up somewhere (generally by doing a short-cut). Then I pull it apart again and do it right.
Given it's age, I would replace the hose from the toilet to the pump. It it's the white sanitation hose, you need to heat it with a heat gun and get it nice and warm to facilitate removing and installing it. It's a pretty simple system. If you have water in the bowl, the bowl is not leaking. Also look at where the pump mounts on the tank. You might be able to hear if there is an air leak here (if eveything else noisy like a/c's are turned off). Also, are you sure it's not leaking where the pressure switch goes into the tank. Those are about the only places it can leak if it's not the tank itself (very rare). Ohhh, one other place sometimes is where the flush pedal goes through I think. Some super lube grease here will temporarily stop the air leak, so you can diagnose it that way. Also I wipe super lube on the bowl seals periodically to lubricate them.
Had a GotYa last year; The base shaft from the foot pedal to the internal base valve has an O ring. After years of use this O ring was deformed. I replaced the O ring, rotated the shaft and reassembled. Just last month, had to replace a diaphragm on an discharge pump. Same diaphragm on the vacuum generator pump. Put a test plug in before the vacuum generator (eliminating the head base) and let it run, if it cycles it's a local issue. if not, look at the head base.
I had a small leak that was hard to isolate last year. It also turned out to be the above mentioned O ring on the foot pedal.