Partially closing stopcock. flow vs pressure

[flutterbye]

I think I understand the principle that partially closing a valve like a stopcock doesn't reduce pressure only flow.


However, we have an external stopcock that is about 100 feet away from the rising main in the kitchen where it enters the property. The external stopcock was recently fitted and is a plastic valve that fully closes by turning 1/4 of a turn.

I was thinking that since the pipework must be at least 100 feet then by partially closing it we might actually reduce pressure at the rising main in the kitchen and so the rest of the house?

I'm thinking that the length of pipe after the partially closed valve should make a different to the onwards pressure.

My view is no doubt rubbish but would be interested to see what others and indeed real plumbing engineers make of it.

 

[dumbrill]

With no flow, the pressure in your supply pipe and house will rise to the mains pressure unless the stopcock is completely closed. Once you open a tap and start a flow then a partially closed stopcock would act as a restriction. You would then create a pressure drop across the valve that would reduce the flow coming out of your tap. BUT a quarter turn ball valve is no good at all for controlling flow. It is either closed or even when slightly turned it is effectively fully open.

Anyway to drop the pressure you should add a pressure reducing valve and leave the stopcock fully open.