22mm supply pipe - what pipe size to use inside?

[Daniel123]

My house was built around 1980, and water mains is supplied via 22mm plastic pipe. At the entrance, it is reduced to 15mm copper which is used throughout the house. I will be changing pipework inside the house soon. My options are:

1. Easiest one: use 15mm plastic from the stopcock. Leave the rest unchanged.
2. Slightly more expensive: use 22mm plastic for every pipe that supplies more than one point, however keep a small run of 15mm copper to the stopcock.
3. Replace the stopcock and the short run of the copper pipe to it with 22mm, and use 22mm elsewhere (as above).

The static water pressure here is 3.1 bar. The short run of copper to the stopcock is about 1m, and the run of the 22mm plastic supply is about 7m. I am currently getting about 12-13 litres per minute. A plumber told me that I will not get any better flow by changing stopcock/internal pipes (in other words, it is the supply pipe that restricts the flow). Is he right?

 

[PrenticeBoyofDerry]

It is likely the incoming supply pipe is actually 25mm or greater.
If you increased the stop tap bore and all your pipe sizes throughout the house, it should increase the flow rate.
But 12-13 l/m is not a bad flow rate.
Why are wanting to change things?

 

[Daniel123]

It is likely the incoming supply pipe is actually 25mm or greater.

I can see 22mm plastic pipe coming from solid floor. I doubt there is a reduction somewhere within concrete?

If you increased the stop tap bore and all your pipe sizes throughout the house, it should increase the flow rate.

That's what I think. Thank you for confirming!

But 12-13 l/m is not a bad flow rate.
Why are wanting to change things?

The flow is not bad, but any demand significantly affects the pressure. For example, if A takes a shower (6 litres per minute) and B slightly opens the tap in the kitchen, the shower flow will drop very notably.

Changing the pipework because upgrading a few areas and will need to move pipes.

 

[PrenticeBoyofDerry]

What type of system do you have?

 

[Daniel123]

It's combi boiler now.

 

[Happyplumber]

There lies the problem,When you have a Combi it can only effectively supply one hot water outlet at time so if one person is having a shower and someone else opens anotber hot tap then they start to share the hot water supply
This is the drawback with most combi boilers unfortunately

 

[Daniel123]

Sure, I understand this. I am talking about cold water. The consumers could be a dishwasher or washing machine, or a toilet flushed. There will always be some interference of course but I guess 22mm should make it less annoying.

 

[JohnD]

I can see 22mm plastic pipe coming from solid floor.

Do you mean the outside diameter is about 22mm? is it black?

Modern metric blue plastic pipe is 20mm or 25mm o.d.

Some older pipe is in imperial (inch) measurements

if you can see enough pipe, the size and brand may be printed down the side.

 

[Daniel123]

It is black plastic pipe. The outside diameter is 22±0.2mm. I couldn't find anything printed on it (only about 80mm length is visible).

 

[Happyplumber]

The old Alkathene pipe black in colour used in the 70's quite a bit. We normally used a 3/4 olive to change over to 22mm on this pipe

 

[PrenticeBoyofDerry]

As already mentioned, a combi-boiler will restrict the demand of instantaneous hot water. But I do not see any issue by supplying cold water appliances/outlets directly from the main in higher bore pipework.

 

[durhamplumber]

Sure, I understand this. I am talking about cold water. The consumers could be a dishwasher or washing machine, or a toilet flushed. There will always be some interference of course but I guess 22mm should make it less annoying.

Less annoying??..does it annoy you then if the washing machine or toilet takes 30 secs longer than usual to fill? ..do you time it..how would you notice..do you stand and watch?..maybe its anger management you need and not wider cold pipes.

 

[rules&rulers]

could fit flow restrictors on all water outlets and remove flow restrictor (if fitted) to combi.

Very much do able.

 

[Madrab]

A 22mm pipe, even older alkathene should give an adequate supply if the dynamic pressure is good. Have you performed a dynamic pressure test? You have given a static figure but it's the dynamic pressure that matters when multiple outlets are opened.

 

[Daniel123]

A 22mm pipe, even older alkathene should give an adequate supply if the dynamic pressure is good. Have you performed a dynamic pressure test? You have given a static figure but it's the dynamic pressure that matters when multiple outlets are opened.

No, it was Affinity Water engineer who tested the pressure, and they only tested static pressure.

I understand there are factors other than pipework to/inside the house, but still my reasoning is quite simple: if I have a 22mm supply pipe, why would anyone reduce it to 15mm at the entrance to the house? I understand hot water is a different matter, but as long as we are talking about cold water?