I have a relatively new pump / tank combo from Canadian Tire (small 5 gal tank with 1/2 horse shallow well pump bolted on top). Runs at 20/40 psi. I've had it for a few years (bought it on sale) but have probably not even pushed 200 gallons thru it over that time. It draws from underground cistern about 100 ft away, probably less than 10' lift to pump (in my crawlspace).
this weekend I added another tank to the system for a bit of capacity. I set the new tank charge also to 18 lb (20/40 switch), bolted everything up, primed the pump and away it went. Everything filled up, pressure hit 40, no leaks or issues, and it ran flawlessly for about 3 or 4 cycles (opened a garden hose and let it run for a short while) - and then it just stopped moving any water. The pump motor was running, zero pressure, there was no visible leak anywhere. I thought it lost prime, but when I opened it up the pump was still full (double checked the impeller chamber, discharge, the suction line, etc. - all full). I couldn't get any more water in the top of the system.
I was thinking about the foot valve - would have guessed if that was shot, it would leak and the water would drain back down to the cistern. But it doesn't. The line stays full. This foot valve is rated to crack open at less than 0.5 lb pressure and I have 1 - 1/4 " suction line - the pump has never had to work very hard. Next trip out I'll swap the foot valve and test but meanwhile my gut feeling is that something in the pump is broken.
I have clear braided tubing on the discharge connection. Usually when I start it up after working on the system, or if it's been off for a while, and if there's a tiny bit of air on the top of the discharge line, I can see the water "boil" just a bit as the impeller stirs things up and starts moving. It will do this while it gets prime. And even with as much as the top half of the discharge full of air (which tells me there's air in the top of the pump too), it still takes prime without a problem. Now the pump kicks in and it's doing nothing - couple tiny air bubbles in the top of the discharge line right at the pump don't even move when the motor starts - like the impeller isn't even trying. I have never had an issue priming this pump - even half full it just takes off. Now the motor starts, and I think the shaft is turning but I think the impeller isn't. Is this possible / likely? can this be fixed? If this pump was 10 years old or pushed 20 thousand gallons I'd be less upset, but it's hardly used.
any sanity checks appreciated - thanks