New water pipe from road - 20mm or 25mm ??

[mark.carline]

I am soon going to be getting my old lead pipe replaced that will feed a three bedroom detached house. The moment the water enters the house it will then feed a 22mm copper supply that tees off to 15mm pipes for each item that has a water supply.

My questions are:

- What size pipe shall i ask the contractor whos replacing my pipe to install ?
- I have seen 20mm and 25mm blue mains water pipe in B&Q when i was looking, Is there a standard that should be used?
- Does it make any difference ?

We currently have the following items in the house that need to supply:

- New Baxi Combi Boiler in the loft (will be fitted at the same time)
http://www.baxi.co.uk/products/productDetails.php?type=consumer&idx=1128&cat=2
- Bath
- Grohe Wireless shower mixer (high pressure system)
- Washing machine / dish waster
- Hose pipe in garden
- 3 x sinks (kitchen / main bathroom / small bathroom)
- 2 x toilets

 

[corgiman]

the bigger the better

 

[mark.carline]

thanks! - Thought so !

Is there anything else I should be asking them for ?

What about stop taps - Are there good & bad ones (compression / push fit etc ) ?

What about these stop taps that have a remote switch on them - Are they any good ?

 

[BoxBasher]

Being in Cheshire I make the assumption that you are in United Utilities area?

They require a minimum pipe size of 25mm for lead replacement.

 

[MANDATE]

You will have to obtain Unitied Utilities approval before they agree to make the connection. They will supply you with specification requirements regarding size of pipe, what pipe may be laid on, depth of trench, how pipe enters property, ducting and insulation within ducting. type of stop tap, oh and a drain cock.
You should be able to view these requirements on UU web site and I think download application form.

 

[chrishutt]

You might even want to consider going up to 32mm (nominal 25mm/1" bore) pipe. It's only marginally more expensive than 25mm and gives you better flow if you're running everything directly off the mains and mains pressure is low.

 

[BoxBasher]

You might even want to consider going up to 32mm (nominal 25mm/1" bore) pipe. It's only marginally more expensive than 25mm and gives you better flow if you're running everything directly off the mains and mains pressure is low.

Some companies will only allow you 32mm if you provide a 32 to 25 reducer (as they only carry/stock 25mm fittings).
The short stepdown won't make that much difference as the benefits of a wider pipe over the majority of the length (minimising friction loss) will show themselves (but if you are only using 22mm copper then the benefits may soon disappear)

UU should allow 32mm (I believe it is the same price) but I would check with them first and wait for the paperwork before starting anything just to be on the safe side.

 

[Agile]

Thames make massive standing charges if you have a larger size supply pipe at the connection point on commercial supplies.

They used to charge domestic 1/2" even if it was 25 mm but I think that was a concession and I dont know if its still in place.

Where can one find graphs of the resistance/flow rates for blue poly pipe?

Tony

 

[BoxBasher]

Where can one find graphs of the resistance/flow rates for blue poly pipe?
Tony

Very useful spreadsheet here

 

[frediaz]

I am doing something similar so I am "hijacking" this post to add a question: if the supply pipe from mains is already 22mm, is there any point in attaching a larger diameter pipe to take the water from the supply pipe -at the property boundary- into the house?

Should it be just one pipe from the street valve into the house or is a connection to the pipe at the property boundary acceptable?

 

[chrishutt]

If your choosing between 25mm and 32mm poly, the larger size will give you slightly better flow, even if other sections of the supply pipework are already 25mm poly or 22mm copper. But do you need the extra flow? Unless you have high flows directly off the main (e.g. 2 or more bathrooms fed by an unvented hot water cylinder) or your mains pressure is very low (say around 1 bar) 25mm poly will be entirely adequate.