My cold water supply to the kitchen is 15mm copper, reasonably straight with no tees, for the 6m or so that I've seen. The remainder to the connection with the main, maybe another 5m, I've never seen but have no reason to suspect it's any different.
There is a stopcock under the sink which isolates the cold tap and a supply to the combi boiler. This is not fully open, I backed it off to just before the point at which it affects the flow through the combi. We have reasonble mains pressure and this stops the cold tap running like a fire hose.
I have a new Pegler tap fitted with conventional washers. When the cold is turned on it starts just fine then dwindles away to nothing in about
5s. Further opening of the tap restores the flow.Any idea what could cause this? Is it likely to be the tap washer and/or is my tinkering with the stopcock setting ill advised? I even wondered if it was a design feature of the tap, attempting to give a consistent flow across variable mains pressure, and failing.