Help - Worried about new plumbing install

[BD_Notts]

Hi,

In my new extension the boiler (a Worcester 42CD1 Combi) is 16 meters from the incoming water main stop tap. The boiler had been connected up on a very long run of 15mm plastic pipe, which has all of the cold water outlets coming off before reaching the boiler.

I'm worried about hot water pressure and after researching I think they have plumbed this in wrongly. The job is not finished yet but the plumbing is in and some ceilings plastered so this will be difficult to rectify but needs doing now.

The incoming main is new 25mm plastic to the stop tap and has good pressure.

Can someone please advise.

Thank you.

 

[Dean744PiN5]

A combi is designed to use 1 outlet at a time, so on that basis a 15mm supply will be fine, providing your incoming flow and pressure are adequate, if you was expecting better performance than this (i.e using multiple outlets at the same time) then a combi boiler was the wrong choice of system i'm afraid.

 

[Madrab]

Is your concern that if you don't have sufficient pressure/flow, when other outlets are being used, there won't be enough pressure to satisfy the combi? Do you see a drop in flow when more than one outlet is being used?

All you can do, and what the installers may have/should have tested, is check that the dynamic pressure and flow to the combi, whilst other outlets are being used, is consistent and sufficient to feed the boilers requirements. If this has been checked as being ok then you have noting to worry about.

If there is an flow delivery issue at peak use, then usually the combi would be placed first on the mains run. If you are seeing a drop and everything is being fed from one distribution pipe, then a larger diameter pipe may be needed but a pipe sizing exercise would need to be performed.

 

[Dan Robinson]

I'd be more concerned about the choice of boiler.

 

[Agile]

A combi is probably the wrong choice of water.

But the poor situation can be ameliorated by adding flow restrictors on the cold outlets connected before the boiler.

If isolating valves have been fitted at each outlet, as required by Water Regs, then they can be used to reduce the flow.

I would probably have used a single 15 mm to the boiler from the 22 mm inlet and then another 15 mm to feed the cold outlets from the same 22 mm source point.

One good installation I saw in a large flat used a radial system of 15 mm tube to EACH outlet from the 22 mm inlet point.

Tony