20mm mdpe to 25mm pipe to boiler?

[diy457]

The builders plumber came today and we discussed the work to be done - replace old boiler with combi boiler into new kitchen extension etc etc.

He said he can put in a 25mm pipe to the water softner then new boiler (valiant 837) from the mains - which is a 20mdpe. And then from the boiler a 22mm pipe and then 15 t-offs - or something like this. He said later i can get the main line changed from the road to a 25mm for max pressure if i get another shower installed in loft conversion in the future.

Can any experts give me there opinion on the above?

I was thinking a 22mm pipe from the 20mdpe and then 15mm to connections.

Will a 25mm from a 20mdpe increase or decrease pressure?

He seemed pretty knolwdgeable on first impressions (and I need to check his Gas Safe card etc next time he comes). I like to double check stuff - better to be sure.

 

[Charnwood]

I’m pretty certain you can’t run MDPE to the boiler due to heat issues.
It would be pointless converting the 20mm MDPE to 22mm copper as 20mm MDPE is the same bore size as 15mm copper.

An expert will be along soon to fill in the gaps.

 

[diy457]

Its not about running the mdpe to the boiler... its about the CONNECTION from the mainline / 20mdpe to the boiler going from 20>25. Will it work? Will it increase pressure or descrease pressure?

 

[Happyplumber]

flow rate flow rate and dynamic flow rate

 

[diy457]

care to elaborate happy plumber?

Im thinking 20mdpe to 25mm pipe (plastic) upto water softener then a NEW stop cock and then down to 22mm copper pipe and then 22mm to the boiler and 15mm t-offs to various outlets....

correct?

 

[Agile]

You may need a short length of copper before the boiler. Ideally at 22 mm.

For the outlet really 15 mm is best to be used and most ideally feed everywhere only in 15 mm otherwise you waste water and heat using a larger tube for the hot.

Check the price if going through a builder who will want to make his cut.

The boiler is probably about £1300 inc and a reasonable installation cost perhaps £900 but that excludes much pipework apart from a shorter ( 3m ) of upgrading the gas supply pipe.

Tony

 

[diy457]

Thanks agile.

So im assuming 25mm from 20mdpe main to water softner is ok then 22mm to boiler then 15mm thereafter.

The plumber's labour is part of the builders cost - included in the overall labour for the kitchen extension already agreed - so nothing to do with me. I just want to make sure he does it the best way.

We have brought the boiler for £1271 and need to buy timer and thermostat so £1300 is spot on.

 

[muggles]

So im assuming 25mm from 20mdpe main to water softner is ok

It's OK but rather pointless, you won't gain anything by going up a size off your existing 20mm, may as well feed the softener in 20mm and the boiler in 15mm, or upgrade your incoming main to 25mm from the street connection