Running cold main to combi in 22mm?

[Thegift]

Got combi in loft 32cdi. Cold mains from 22mm stopcock reduces in 15mm right after the isv then runs up through the loft to combi with one tee on the way feeding into bathroom.

Water pressure ok but could be better, ideally need to replace the black Alkathene mains which im putting off at the min.

About to start to refit the bathroom so the mains will be exposed, would it make a difference to run the main in 22mm from stockcock and reduce into 15 just before boiler in the loft or will it not make any difference ?

ta

 

[SimonG]

It will make no difference. Have you measured flow of hot and cold? Whats it giving you? At the end of the day its a combi with a max flow rate.

 

[Thegift]

Cold is 16lpm on kitchen sink and hot is 9lpm

 

[SimonG]

Whats the max spec for the combi on the hot water flow?

 

[Thegift]

13.1 litres per minute at 35 degree temperature rise

 

[Centralheatking]

You are lucky to 16 ltres per min on the cold main - folk in London would
die for that volume. 9 ltres per min on thehot is not the end of the world.

But what is the temp. rise ? in summer the combi boiler is coasting I would
wait till a cold winter morning - you might be gratefull for hot water at 9 litre
per min then


Centralheatking

 

[AWheating]

making the combis 15mm cold feed the first connection after your stop tap would help alittle with hot water flow rate . If you have mixer taps the supply will always be shared of course.