Pump's quieter with some back pressure?

[flyboy320]

I have a Jandy 2hp single speed pump. I have downstream of the pump, a shutoff valve and I find if I turn the shutoff valve so it's about half way closed, and creating some back pressure, the pump seems to run much quieter. There still seems to be the same amount of water coming from the water jets, so I don't think it's reducing the water outflow much. Because the pump is located beside my house, I would like to run it as quietly as possible. So I'm wondering if running the pump this way can damage it, and is this a "normal" behavior for a pump?

 

[JohnT]

I have upstream of the pump, a shutoff valve and I find if I turn the shutoff valve so it's about half way closed, and creating some back pressure, the pump seems to run much quieter.

Upstream would mean before the water gets to the pump, which would reduce the pump pressure.

What does the filter pressure gauge do when you partially close the valve?

ETA: Is your pump 2HP like your post says, or 1HP like your sig says?

 

[flyboy320]

Thanks for setting me straight John...

Yes, the valve is in fact downstream of the pump (my post above is edited to reflect this).

Yes, it is a 2hp pump (sig also edited)!

The pressure gauge maybe increases by 5psi at most when I partially close the valve (reading from the pressure gauge on the filter which is also downstream of the pump).

 

[mas985]

Yes, pumps usually do run quieter with more back pressure. But in most cases it is because the flow rate is reduced with the extra head loss. A 5 PSI pressure increase is an increase of over 10' of head loss so the flow will be reduced by quite a bit. But that is probably why the pump is quieter.