15mm or 22mm?

[richardrich79]

The copper Hot water outlet from my condensing boiler is 15mm copper for the first couple of metres then joins 22mm up to the first floor where it reverts back to 15mm.
I guess the copper 22mm is a hangover from when the hot water tank was upstairs.
My question is,

Is there anything to be gained by using 22mm instead of 15mm to the 1st floor shower ?

The shower has good pressure, no problems there, I just don't want to lose any advantage the wider pipe may give.
I'm replacing the pipes anyway as they do not take the shortest route and are currently uninsulated.
Please bear with me if it's a stupid question but I just cannot get my head around when to use 22mm pipe.

 

[footprints]

Depends if your condensing boiler is a combi or storage with a cylinder, I am guessing it's a combi.

Anyway if it is a combi reducing to 15mm will have little effect on pressure but will slightly reduce the time it takes for hot water to reach the shower, because there's less cold water to move out of the pipework before the hot gets there.

If it is a storage system working on gravity reducing the pipe size will adversely affect the pressure at the shower.

 

[richardrich79]

Sorry I should have said it's a combi. Thanks