Pipe speccing

[Riley]

Dilemma with pipe sizing chaps, doing some install work for my old mentor while he recovers from an op.
Job is a complete refit of a small two bed flat.


He has specked this job down to the last detail so I have literally just had to turn up and start installing.


He has stated to install 15mm hot and cold runs running from the kitchen where the boiler is to the bathroom so maybe 3m runs in total for each run.


Customer is being annoying now saying that he wants the additional flow of 22mm on these runs. For such a short run is it going to make noticeable difference to the flows? It's only a 25kw combi going in so the LPM is only going to be so high anyway?


Would you agree?


The customer is a website surfer and had a list of plumbing related questions lined up for me when I arrived. All of these I've answered satisfactorily but I just want to put his mind at rest that 15mm will be sufficient.


Your thoughts please.

 

[ShaunCorbs]

how many t offs?

 

[Riley]

One going to bath and basin that's it. Toilet on separate feed

 

[Dotty]

Point out to the knob jockey that you're installing pipework as designed for a higher pressure and flow rate system than a gravity system. Which, no doubt, is what he's looking at.

Buuuuuuuuut if he insists on 22mm he should be made aware that it'll cost more than he's agreed to......

 

[Riley]

Well that's my thoughts croppie and it's all in and under floor now. If he insists I'll do it but as you say on pressurised there's just no poiny

 

[ShaunCorbs]

One going to bath and basin that's it. Toilet on separate feed

will be fine then

he does know you cant run more than one outlet at the same time without reducing flow ?? 😀

 

[Riley]

I believe it was explained in some depth. But we'll see

 

[KingDoey]

My hot run is about 9 metres in 15mm and tees off 4 times. Got 30kw boiler and it still nearly rips my skin off at every outlet!....

 

[Riley]

Thank you. I'm now happy to tell him no

 

[Last Plumber]

If you use 22mm on that installation, it will have a cooling effect on the DHW and it will all be your fault !

Just saying !!

Just thinkin of you, I'd refuse point blank

 

[Last Plumber]

If you use 22mm on that installation, it will have a cooling effect on the DHW and it will all be your fault !

Just saying !!

Just thinkin of you, I'd refuse point blank

 

[oz-plumber]

You could also inform him that the time taken for the hot water to come through to the taps will be around double with 22mm pipe.
He will also be wasting alot of water.

 

[tolly]

Pointless running the DHW on a 25kw combi in anything bigger than 15mm, you will still get only get 10LPM whether its run in 15mm or 54mm, would just give you a bigger dead leg volume of cold to pull through before the hot arrives at the outlet.

 

[Millsy 82]

I can understand the cold ran in 22mm to get rid of turning a tap on and the pressure drops but the hot will be a waste of time and just waste water.

 

[oz-plumber]

The customer is a website surfer and had a list of plumbing related questions lined up for me when I arrived. All of these I've answered satisfactorily but I just want to put his mind at rest that 15mm will be sufficient.

Simple solution to this..

Just get the customer to put it in writing.
Make sure he states that he understands that 15mm pipe will be suitable but he requests 22mm pipe to be installed.

Do what he wants and let him deal with the slow hot water lag.