Pump Noise, Quiet With Spa, Loud With Pool

[Nickelii]

Hi. My neighbor has a pool pump that is in between our houses and the sound echos between the buildings really loud. They are new owners and they seem to be doing something different than the previous owners. A few years ago the new owners installed a new pump, a pentair whisperflo and it was a great improvement over the old pump.

The new owners moved in and something is different as the new pump was never this loud on how the old owners ran it, or maybe they were doing something wrong.

Anyway, here is the setup. eThe pump runs for both the spa and pool. When the valve is set to filter the spa, the pump is reasonably quiet. I mean, we can hear it but it isn't a bother. When the valve turns from the spa to the pool, it becomes loud.

I talked to the new owners for about 30 minutes yesterday. The pump appears to be a single speed pump, so in theory shouldn't it be just as quiet when filtering the pool as it is when filtering the spa? Is it air in pipes? If yes, why would it get air in the pipes with the pool but not spa?

The neighbors are pretty reasonable and want to make it more quiet but this is new to them. They said a pool guy looked at it and he called it "normal" but that doesn't sound right. I mean, same pump, same speed, loud with pool, quiet with spa?

Ideas?

[Pool Clown]

Possible some kind of an obstruction in the pool suction line. What is the pressure on the filter tank in pool? In spa?

[Nickelii]

Good question. I did not see a gauge anywhere in his lines, not to say there isn't one. What would be normal? If they are different, would you expect the pressure when the pump is running the pool to be lower or higher than the spa?