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Discuss 10mm pipework for cold water..why not? in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Messages
49
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?
 

Ric2013

Plumber
Messages
2,757
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.
 
Messages
49
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
 
Messages
49
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

Esteemed
Plumber
Gas Engineer
Messages
4,779
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
 
Messages
49
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.
 

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