Suction side leak?!?

[red-beard]

Today I replaced my pool temp sensor which had been acting up. I shutdown using service mode as usual. I replaced the sensor (easy job). Then turned the system back on.

Pump basket was not filling with water. Water is coming in, like during priming. But not filling up as usual. This is a VSP, so I pressed the button to give me full blast (3450 RPM), which is also priming speed. Water is still not fully filling the pump. Hmmm.

Since this pool was originally a 2 pump pool (why???) I switched it over to the "Boost" pump. It also can't fill the basket. I think I have a suction side leak. Pool was working, are it appeared to be working before I shutdown. I have switched back and forth on the motors and it definitely seems I have an air leak.

Any thought on trying to find the leak? I can't hear anything around the pumps (too loud).

Pool temp sensor is downstream of the pump, on the pipe to the filter. So that is not the source.

 

[mknauss]

Check that the weir door is not stuck.

 

[red-beard]

Both skimmers are full of water

 

[Summoner12]

How long did you let the pumps run? are your valves fully opened on your suction side? When I have my rover plugged into the skimmer connection and the pump is running at high speed the basket area of the pump has a big air bubble.

I would tru running at a lower speed with all ports fully open, also vent the filter if any air is trapped in there and then check back after a few hours of operating.

My LPS told me I had a suction leak, said it was the ONLY way I could have air bubbles coming out of my return. My pump could run with zero air in the basket and still have bubbles at the return. Turned out to be a crack in a pipe on the pressure side and a leaky valve... low speed operation leaky valve sucked air from cracked pipe that had no water in it.

 

[red-beard]

Valves are in the right places. how long did it run like this? Not sure. It seemed to be operating OK before I changed the thermistor. I saw water going out of the spa.

I think it is the seal on the pump pot on the booster pump. I did not see air coming in on that line when I ran the booster, but I was still getting air. This gasket has not been changed in 13.5 year.

 

[red-beard]

First, a little background. This pool has quite poor equipment design, I think intended to maximize price! There are two "main" pumps pulling from the same suction, side by side. Originally, one was supposed to be (low) 1/2 hp and the other (high or "boost") 3/4 hp. Why a 2 speed pump wasn't installed, I'll never understand. And the "low" speed is a full 1/2 hp (which was replaced with a 1HP pump a month after original startup!). So again, these pumps are in parallel, and never run at the same time.

I replaced the "main" pump four years ago with a VSP. My automation can't control the pump speed. So I just use the automation to provide power (on/off), the speeds and timers are programmed on the pump. Generally, the only use for the "boost" pump is when I need to run the heater. My regular "speed" for the main pump is low enough that the heater refuses to run.

I looks like my skimmers became VERY clogged with leaves, restricting flow. This created high suction when the pump ran at high speeds. And this high suction caused the 13 year old pump o-ring to leak.