Central Heating 28mm to 22mm Best Practice

[sijones]

I have 28mm pipework for the flow and return to my boiler. This is reduced to 22mm as shown in the simple drawing below.



From my layman's point of view I think it would be far better to have 28mm all the way to where the pipework connects to the 22mm pipes using something similar to a 22mm x 28mm x 22mm tee. It is currently reduced to 22mm and then connected to a 22mm x 22mm x 22mm tee.

What do you think?

Kind regards,

Steve

 

[cr0ft]

It would probably be 'better' although whether it would provide any real benefit is another thing. You would have to have an awful lot of radiators on your system for the 22mm pipe to be acting as any sort of restriction to the system heating up. Based on 1.5m/s flow rate through the system and a 20C temperature drop round the circuit 22mm pipe can carry 40.2KW of heat output. That is around 3x as much as a typical domestic property requires. If your house needs 67.5KW then upgrade that bit to 28mm but I suspect it doesn't.

Short answer, I think you are worrying over nothing!

 

[kay-jay]

Its fine.

 

[Best]

Yes, it would be good practice to 'split' each 28mm pipe into 22x22x28 tees so that you get the full bore of the 28mm. That's certainly the way I do it. But it won't make a lot of difference to flow if the 28 mm is reduced to a very short piece of 22mm, as it is the length of the pipe that can cause resistance, not just the bore.
When you look at how motorised valves inside their brass body have a very small opening compared with the pipe they are on, it does show things are not ideal.

 

[Rickster123]

More importantly how did you get on with getting your gas fire fitted last year??

 

[Best]

2 of 22mm tees with 22x28 reducers are perhaps a lot cheaper than 2 of 22x22x28 tees & that could be one reason why it was done that way.

 

[Ermintrude]

Wouldn't worry about it your boiler probably only puts out 35kw to ch any way!

 

[happyflyer]

Wouldn't worry about it your boiler probably only puts out 35kw to ch any way!

Good answer Ermi, you are probably right, no one else thought of that and its a basic, HWS load and boiler oversized on design or guessing game plumber,
always add a bit on just in case, wonder if the gas connection is only 15 mm for the last 3.5 mtre , might even be oil burner, jeez all these technicalities
plumbers are not paid enough for all this tosh. Anyway the little sketch looks out to me, but these none trades are really putting us under a bit of pressure
with their pointed questions about pressure drop, we will need to be careful how we answer these.