MDPE 32 or 25mm into the house

[seb963]

Hi,

I have just had Thames Water upgrade my mains connection to a 32mm MDPE, however my builder has run a 25mm MDPE after TW stopcock from the property boundary into the house, hence I am wondering if this would have already reduced the pressure I would have had into the house. I would have expected him to run a 32mm MDPE.
The house is now on mains pressure system (converted from gravity fed system to unvented with HW cylinder) with one bathroom, but I have the plan to add a second bathroom in the loft, and I am worried that the pressure will not be enough on the 25mm pipe. The pressure on the first floor bathroom is better than with the old gravity fed system but not exceptional.
The question is whether a 25mm is ok, or should the builder have gone for 32mm for the mains inside the house? Having paid £1100 for the TW upgrade, I want to make sure this was worth the money!
For reference the flow at the cold tap in the kitchen is about 10L/min, and reduces to 6L per min when all cold taps are opened at the same time (bath, bathroom tap, kitchen tap)

Regards

Matt

 

[ShaunCorbs]

you have a bigger problem if your only getting 10lpm (mains water) for an unvented system you need upwards of 25lpm

also what did thames water say your max/ min pressure or flow rate was?

 

[Dotty]

It won't reduce the pressure but it will reduce the flow rate as above.

What did the builder specify in his written quote?

Though you should really have employed a plumber......

 

[seb963]

I have measured it myself (probably not very well!) by filling in a 1l bottle in 6 seconds... TW did not mention the max pressure

 

[ShaunCorbs]

sounds like either wrong system if tw can only supply you with what your getting or right system depending on what tw can give you could be a half shut valve or a few things that will reduce your flow

 

[mfgs]

What flow rate did you have at the kitchen sink before the upgrade?

 

[seb963]

I had about 6L per min from memory

 

[ShaunCorbs]

I had about 6L per min from memory

are you sure you have an unvented cylinder and not a cylinder with a tank in the loft / above it ?

 

[joni os]

Length of 25mm MDPE is a factor. Thames Water should be able to confirm pressure at their meter, expect 3 bar+, but flow through meter also important. Not unknown for faulty meter to restrict flow if upstream works were not properly cleansed. Your meter may be 3/4", changing to 1"will increase flow.
OP is silent regarding upgrade of internal pipework, new stopcock and feed to unvented should be sized to suit.

 

[Dotty]

I have measured it myself (probably not very well!) by filling in a 1l bottle in 6 seconds... TW did not mention the max pressure

About 10 litres/min