About six months ago, I had a drip system installed. A pressure reducing valve was installed to knock down the water pressure so that the emitters would not be blown off by high water pressure. The valve is now making a whining noise when water is traveling through it. The valve is black plastic, about 10" in length, and has a knurled plastic knob on one end. This knob would appear to turn, but it does not.
Can I adjust this valve and make the noise go away?
Adjust the valve if you want, while monitoring the performance of the water emitters downstream. You do not want to comprimise the performance there.
The sound you are hearing is the PRV doing its job: Reducing pressure. On my back porch I have a PRV threaded to many tubes to water many hanging plants and such. It squeals on occasion when I turn the water on to nourish these plants. It's not bothersome as the valve is only open for 5 or 6 minutes.
Measure Twice, Cut Once