15mm or 22mm supply into new bathroom

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Oxford
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Hi,

I am having an extension with a new downstairs bathroom. I have a new vaillant ecotec 937 on the wall ready to be plumbed in. I also have a new 25mm MDPE supply pipe inspected and about to be connected to the mains. I live at the bottom of a hill and static pressure is 4-5bar.

The issue is the supply from the stopcock to the downstairs bathroom and utility room. I asked the plumber to run a 22mm pipe from the stopcock to the bathroom. However, he chose to use an existing section of 15mm pipe just off the stopcock that I am afraid will cause a flow restriction downstairs.

Basically the 25mm MDPE goes into a short 22mm vertical section up to the stopcock. The existing 15mm upstairs supply (to electric shower and sink) goes straight up from there. The downstairs supply goes through a tortuous 4 elbows in copper, with branches off to the sink and dishwasher supply, before it goes into 15mm plastic back down to the floor(see photo). There is goes back into 15mm copper, then into a 22mm elbow then into 22mm plastic (see 2nd photo). The rest of the supply to the bathroom, and to and from the boiler, is all in 22mm plastic. This supply goes into the boiler, cold supply to the bathroom, 2 outside taps and a washing machine supply.

My grasp of fluid dynamics is basic but I believe that this section of 15mm pipe potentially restricts the maximum flow to the entire system. This is doubly so considering how tortuous the run is, which must disrupt laminar flow and increase effective resistance.

I have bought a ridiculously oversized 500mm diameter rain shower head for the walk-in shower, which I want to run simultaneously with a shower riser head inside the shower, hence the massive boiler. I am concerned that if any of the other outlets are open (or especially multiple ones), I will end up with a restricted flow to the boiler and shower.

At present the celotex and UFH pipes are laid and the screeders are coming tomorrow.

Basically I need to know if I am being unreasonable insisting that they re-do that small section of pipe in new 22mm. 3 plumbers have apparently insisted that it will make no difference. Advice would be appreciated ASAP.

Thanks in advance



 
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I have bought a ridiculously oversized 500mm diameter rain shower head for the walk-in shower, which I want to run simultaneously with a shower riser head inside the shower, hence the massive boiler. I am concerned that if any of the other outlets are open (or especially multiple ones), I will end up with a restricted flow to the boiler and shower.

Fail number one.




Is the offending bit of pipe accessible?

If so then get them to change it if only to keep you quiet.
 
I have bought a ridiculously oversized 500mm diameter rain shower head for the walk-in shower, which I want to run simultaneously with a shower riser head inside the shower, hence the massive boiler. I am concerned that if any of the other outlets are open (or especially multiple ones), I will end up with a restricted flow to the boiler and shower.

Fail number one.




Is the offending bit of pipe accessible?

If so then get them to change it if only to keep you quiet.

Dan
You come out with some belters
 
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I'd be more concerned about the cold mains pipes in a heated floor screed!!!!...... :eek:

Your large shower head will be a breeding ground for legionella!! And a nasty slime will form inside the cold water plastic pipes!!! Good luck with that also.
 

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