Aft Vacuum pump

[bwilson]

When I go to my breaker panel to turn on the aft head, you can hear and see the pump working (piston moving up and down) but the pump never shuts off. I need thoughts on what to look for to correct this problem.

Thanks

[Viper]

Could be a number of things but most common is the check valves need to be replaced. Typically in the line right at the pump; 2 before and 2 after the pump.

Is there water in the bowl (head/toilet)? If not, chances are you need new seals there. They seal around the ball in the bowl to prevent the water from leaving the bowl in a rest position. Water in the bowl assists in making an air tight seal. Sometimes it's just a dity seal in contact with the ball that causes a leak.

If you are getting a good vacuum when you flush and it's evacuating everything but the pump simply never shuts off, you could have a small enough leak somewhere or your presure switch might be faulty.

Lastly, if there are no leaks and it is not generating a vacuum, the pump components themselves may need to be replaced.

[bwilson]

Viper,
Water comes into the toilet and stays....it does not leak. When you flush there is great vacuum that pulls waste into the waste tank, but the pump still runs so I just shut the pump off at the breaker when the toilet is not in use.

[Viper]

You either have a leak in the line at one of the fittings, a pump leak, or need to replace the check valves. The valves are a regular maintenance item, if you haven't replaced them for several years, they are likely the culprit. There is a vacuum switch that shuts the pump off once it reaches spec but they don't go very often and are pretty expensive. Check the valves. Once they are removed, inspect them. If they are even slightly open (if you can see through them), that's your problem. Replace all 4 at the same time.