Every since I bought this house 1.5 years ago, I've had a persistent problem with a suction side air leak that's been getting progressively worse. I went through all the usual suspects around the pumping pad: pump drain plug, o-rings, valves, fittings, etc and never had any luck. Finally, I got the shovel out and started digging underneath the pump pad.
Above the pump pad, there's a mixture of copper and PVC plumbing, so I was hopeful someone had done a retrofit to the pumping area and there'd be a leaking copper-PVC union near the pump pad. Well, no such luck.
But, on a whim, I got the garden hose out and filled the freshly dug hole full of water. Immediately upon filling it, in the pump basket still showed air. Bummer. But, a few minutes later, I came back and the bubbles where gone. Hmmmmm. After the water was absorbed into the dirt, the pump basket remained bubble free. But, 5-10 minutes later, they were back again.
Repeat experiment a couple of more times, and sure enough, a few minute after the hole is filled or drained, there's a response in the air-leak. So, my leak was not tooo far from the pump pad. More digging meant taking down the fence; so fast forward a month later...
My water experiment had long dried up, but as I dug I start getting to some very wet soil, and voila:
A coupling that was so very poorly glued that the pipe was literally slipping in/out of the coupler as I dug around it out. I'm amazed the pump ever pulled prime at all from that.
Just sitting by the pool now, waiting for a few more inches of water to drain out before I cut the pipe and patch it up.
Aint pool ownership fun