Combi boiler connections

Author
Discussion

_Al_

Original Poster:

5,578 posts

259 months

Tuesday 25th July 2017
quotequote all
More questions for all you fine knowledgable people..



Our recent combi boiler installation was done when we had 15mm mains inlet to the property, so as you can see in the image we have 22mm pipe for the heating circuit but 15mm for everything else. We now have a 25mm mains inlet and the water pressure is fantastic, but I'm wondering if I should run 22mm upstairs to the bath taps.

I'm an amateur but quite handy with the pipe bender / end feeds / soldering now so happy to take it on myself but I'm wondering if it's worthwhile?

My builder says it's absolutely essential to get a half decent flow rate. The guy who did the combi says it's unnecessary (pressure is fine and the bath will fill quickly / shower will have plenty of flow) and may even be counter-productive (standing water volume rises so takes longer to get hot water out). The boiler is kitted out with 22mm outlets so it's clearly capable and the manufacturer said "do whatever you like".

Any suggestions?

If 22mm is good, where do I get the connections? My local wickes / bunnings / screwfix didn't seem to have anything useful but I may just be searching for the wrong thing.

Rickyy

6,618 posts

220 months

Wednesday 26th July 2017
quotequote all
It'll make little difference. The flow rate of your hot water is defined by a flow limiter built into the combi. 15mm copper will happily provide a flow rate of 20 litres per minute, a 30kw combi will give a 35c temperature rise at ~12 lpm.

LookAtMyCat

464 posts

109 months

Wednesday 26th July 2017
quotequote all
As above; 15mm pipe will easily pass more than the flow rate from your combination boiler, so don't waste your time.

If you want much higher flow from the hot water then have an unvented cylinder installed. You would be able to use your existing combination boiler to heat it. I have done a few installs where the water heater side of the combi is used for a nearby, low-flow requirement outlet (like a kitchen tap) and then an unvented cylinder to feed baths/showers.

_Al_

Original Poster:

5,578 posts

259 months

Sunday 30th July 2017
quotequote all
Ah ok thanks gents. That makes life a lot easier (and slightly cheaper). We do have good water pressure round here so I was surprised when the builder said to change to 22mm.

Hopefully the house will only be in pieces like this once so it's now or never and I wasn't wanting to plug it all in and find out we had a bath that takes days to fill.