Pump Noise

[Piney]

Greetings--

Just ran into this for the first time--

PacFab 2hp pump- round case on front of motor. Appears to run fine-- pressure OK, normal noise.

Until......

I reduce the backpressure by opening the fountian valve. This valve diverts the water from the pool's jets to a fountian. When I reduce the backpressure on the pump even by just a little, the pump begins to make a "grinding" noise.

I didn't notice this last year-- only recently.

I took the pump cover off-- nothing stuck in the impeller. It rotates freely.

Suggestions ??

[thepoolman1]

What you are hearing is cavitation. That 2hp pump is trying to pump out more water than it can bring in. Best option - downsize.

[Piney]

Cavitation, eh ? I'm familiar with that concept as we have jet skis. THeir wear rings when worn and the intake comming 'unhooked' from the water, cause that issue with their pumps.

Why would this just now show up-- after 3+ yrs of operation ? I dont see any air getting into the pump strainer. The pressure on the filter remains the same as in prior years.

Downsizing the pump/motor--

Reduce it to 1.5hp ? Would this cause other issues with the filter/piping as it was designed ( I assume...) to use the 2hp pump ?