What size should my water supply pipe be ?

[rik08]

Whilst having an extension done, the plumber has moved the mains water stop valve. Someone has mentioned my pipe size is only 15mm and should be 22mm.
My water pressure is good but if i have 2 taps on the pressure drops, is this due to the pipe size ?

[plumbbob]

Low water flow could be partially due to a small bore pipe especially if it is a long run. It could also be due to a leak somewhere along it's length and it may also be partially blocked with limescale.

If it is 15mm (probably copper?) then the chances are it is reaching the end of it's life. Underground supplies have never been 22mm. There was either 1/2" or sometimes 3/4". 15mm or more likely 1/2" copper, was generally only used by "non" tradesmen (as it can corrode quickly underground) for the short period between iron pipe falling out of favour and the introduction of plastic. The choice now is mdpe in either 25mm (1") or 32mm (1 1/4")if the house is large or the pipe run is long.

[htg engineer]

Don't confuse water pressure with flow rate. It may be that your street/area suffers from low pressure. Flow rate on the other hand can be affected by pipe size, kinks, damage etc.