Re: Troubleshooting Fresh Water System
We just dealt with a similar problem. We noticed after de-winterizing that we had intermittent spitting of air (but not always!); pressure variation, at times quite low, then would flow with more pressure, then repeat; and unless water was flowing really well, pump would not shut off (prime). With all these symptoms, and no obvious water leak or visible problem with system, we were stumped and thinking we had to replace the pump, or pressure switch was shot, or debris in pump... our research made the possibilities seem endless.
Then, thinking it through led us to realize that just because no water is leaking out, air can still be leaking IN. Start with that. We have two tanks, with two runs of hose (with a strainer each) into our water pump. Because we did have the "spitting air" symptoms, we thought we should consider that as the cause first. We looked at both strainers for loose cover or hose fitting or a even a crack. nothing. Then, my husband tightened each clamp on the hoses connecting to the water pump from both water tanks. just a little tightening. VOILA !! System is now working fine, no air spitting, pump shuts off like a charm as soon as you shut off faucet. Pressure is consistently good! All our problems seemed to be caused by a minimally loose hose fitting. Because we have two tanks feeding the pump, and a line that extends to galley sink, head sink, bow washdown and stern shower, we were overwhelmed when considering how to troubleshoot this situation. LESSON LEARNED: start with the simplest (and most likely) cause first. Start from your tank(s) and tighten the clamps and inspect each connection. Just because you don't see a leak doesn't mean that air isn't leaking INWARD. Don't make our mistake and jump to the worst case scenario that pump is shot! All of the symptoms we had were ultimately caused by a leakage of air into the system, before the pump. Check that first! and Good Luck.