bath / pipe size

[Peat]

I have recently had a new combi boiler fitted,and am shortly going to install a new bath,i was wondering if its ok to run 15mm pipe to the hot tap or should i use 22mm as i am moving position of bath,any help appreciated.

 

[keyplayer]

I am not a plumber but whilst doing a similar job at home recently I had to work with the fact that 15mm pipe was supplying my bath and was buried in the concrete floor, so 15mm it had to be (couldn't be doing with relaying floor) Seems to work well enough, I would imagine 22mm would fill the tub quicker, but its not an issue for me.

 

[AdamW]

I too am not a plumber, but what comes to mind is that whilst you might expect 22mm pipe to fill the tub quicker, there is literally twice as much water in the pipes between your boiler and the tap. And the pump in the combi is pushing that greater mass of water.

In addition, you will run twice as much cold water into the bath before the hot water starts coming out.

So I think that 15mm would be adequate. It is also easier to work with and the fittings seem more plentiful.

 

[HenryRoot]

I have recently had a new combi boiler fitted,and am shortly going to install a new bath,i was wondering if its ok to run 15mm pipe to the hot tap or should i use 22mm as i am moving position of bath,any help appreciated.

If you can, use 15mm. You will find the combi responds to changes quicker that way. The pressure will also be higher, obviously.

 

[AlanE]

Unless a long pipe run is necessary size of pipe is imaterial. Flow rate of combi is the limiting factor.

Alan