Hi
I have recently bought a home with a well system which is new terrain for me.. The line from the pump to the pressure tank has developed an intermittent whistle/high pitched hum that I have narrowed down to the Dole flow control valve. The whistling has gradually become more constant...

The flow control valve is 4 GPM
I don't know what model of submersible pump I have, but believe it to be a 1/2 HP gould.
I lose volume and pressure with too much demand on the system ( A sprinkler zone and running a tap in the home )

I am wondering if my pump is weak or if perhaps my well cannot keep up with the demand.
Any help /suggestions would be appreciated...

Thanks Troy

Dole Valves always squeal a little when used with a submersible pump. The valve will not allow the pump to supply more than 4 gpm (that is why its there). You should ensure that you are not asking for more than 4 gpm. If you are not asking for more than 4 gpm and still losing pressure most likely you need a smaller dole valve because the well is not able to deliver 4 gpm.