Hi. I need some help please. Our cold taps and toilets make a squealing noise. I've tweaked the stopcock (always had high pressure) and service ball type vale above and it's helped. It's only there a bit now and still when water shuts off from fluid master toilets (sqeeeeak as they shut off) do I need a new stopcock? Doesn't seem to shut off water that well anyway. Running out of ideas. Thanks (even thought about prv)