10mm pipework for cold water..why not?

[hometech]

why is 10mm pipe not used for taps/toilet outlets?
Why do I need the same diam pipe at the wash basin or toilet as I do at the bath or shower?
I can't think of a reason why not so before I implement this, have I missed something that's not so obvious to a layman?

 

[exedon2]

Often done on new build tho the taps on new build are often deliberately restrictive to meet water usage targets.

 

[Ric2013]

Probably largely historical, and possibly dictated by low water pressure in some areas. We traditionally used 1/2" which is very close to 15mm OD. Also, 10mm tends to be soft copper which is not easy to make tidy enough to have on show (nor, arguably, robust enough to be exposed).

From a practical point of view - no reason. As you say, taps and cisterns do not require high flow rates.

 

[hometech]

I've just conducted flow tests using 15 and 10. The difference in flow rate was negligible but the pressure from 10mm will cut concrete.

 

[TimboTwo]

"...but the pressure from 10mm will cut concrete."

Better use steel basins then. 😄

 

[hometech]

"...but the pressure from 10mm will cut concrete."

Better use steel basins then. 😄

it measures 10bar

 

[Ric2013]

What method of measuring pressure is giving you a reading of 10 bar?

 

[king of pipes]

It's often used nowadays bud pressure wise 3 - 6 bar is not unusual for mains supply,10 bar seems a bit high ??

 

[hometech]

What method of measuring pressure is giving you a reading of 10 bar?

I cobbled together a system using a regular pressue guage, some tap connectors and a valve. It has a push fit connector to swap between 15 to 10mm pipe. So I can measure static and working at any outlet

 

[hometech]

It's often used nowadays bud pressure wise 3 - 6 bar is not unusual for mains supply,10 bar seems a bit high ??

but I have no issues using a combi and a continuous water heater simultaneously lol. This is what I'm getting from the mains as I removed the PRV on the MDPE feed. I'm now going to have to modify the pipework to add a new 15mm line to provide the entire house with cold water and I'll be adding a PRV to this line so as not to interrupt the flow the the heaters

 

[king of pipes]

I am not disagreeing with you but please be aware high water pressure will damage your water heater and combi , your manufacturers instructions will guide you, prv 's are fitted for a good reason many plastic components are used in boilers ,water heaters , toilet cisterns flexible tap connectors these are not designed or manufactured to with stand 10 bar working pressure it will cause abnormal wear and tear , resulting in a failure and severe water damage to your property ,which you may possibly be not covered for at that pressure. My advise would be replace the prv and adjust it to 3 bar working pressure 21 litres a minute this should be a good average pressure . Kop

 

[hometech]

I am not disagreeing with you but please be aware high water pressure will damage your water heater and combi , your manufacturers instructions will guide you, prv 's are fitted for a good reason many plastic components are used in boilers ,water heaters , toilet cisterns flexible tap connectors these are not designed or manufactured to with stand 10 bar working pressure it will cause abnormal wear and tear , resulting in a failure and severe water damage to your property ,which you may possibly be not covered for at that pressure. My advise would be replace the prv and adjust it to 3 bar working pressure 21 litres a minute this should be a good average pressure . Kop

instructions are that if pressure is over 18 bar (combi and WH) then it needs dropped down. (they also accept propane/methane without any modification and can be placed outside without protection unless the temps drop to -20) (other than a dip switch)). Push fit fittings far exceed the ability of copper solder joints to withstand pressure. 3 bar gave a flow of 8 l/min which is why I had to experiment. I initially thought I would have to install a pressurised water tank to keep up with flow demand . I have had a single pushfit stop end pop but that was on the hot water supply. It was of those with the steel teeth so cut and swapped with JG fitting and no problems. I swapped out the old toilet cisterns with quality Gerbit sigma who are good for 10 bar on the data sheets.

 

[king of pipes]

Good luck with that then I'm out 👍

 

[Ric2013]

I'm not saying you NEED a PRV or you don't need one, but do be aware the reason your old PRV gave 8lpm when set to 3 bar was it was defective and not maintaining that 3 bar, not because a working PRV set to that pressure would restrict flow to that extent. So I would not rule out use of a PRV based on your experience of the old one alone.