Problems running multiple outlets with unvented system in new build

[jimmy84]

Got a brand new 25mm hdpe incoming main with pressure of 2/2.5 bar. Need to check flow rate but doesn’t look great at kitchen sink. The main connects to stopcock and is run in 28mm directly to cylinder which is located on 2nd floor of a town house. Hot and colds are run out in 22mm. It serves a shower and basin on the same floor, a main bathroom on 1st floor and WC on ground floor. Shower runs ok on top floor but when opening bath on 1st floor it pretty much stops. Any ideas on problems? Mains has been flushed and combination valve checked for debris etc.

Jim

 

[king of pipes]

Sounds as if its a supply issue this is becoming a common problem especially in 3 storey town house's there's such a demand on the water supply that the pressure is a lot less in the main you need a constant 3 bar and 20+ litres a minute flow firstly check your stopcock is fully open and any supply valves, water pressure and flow is decreased the higher the water has to travel multiple outlets running will result in poor performance if no faults are found , it may result in you needing a accumulator or a booster pump to achieve a satisfactory performance. Regards kop

 

[Vee]

Always measure main before recommending unvented or mains reliant systems. 3bar and 20litres/min a good minimum guide. Design outlets and pipework to cope with simultaneous demand.

 

[ShaunCorbs]

Could be some strainers need cleaning as it’s a new build

 

[Timmy D]

Is that static or dynamic pressure? I guess static, which in real world terms, is pretty useless.

 

[jimmy84]

Pressure at incoming main is 2 Bar with a flow rate of 7 litres per min.

28mm main runs to top floor of a townhouse so 2nd floor. Goes through combination valve at cylinder which is completely clear of debris and is working. Balanced cold then runs down to ground flooring 22mm, teeing off for top floor bathroom, teeing off for 1st floor bathroom and ending up at utility on ground floor

flow at utility sink on balanced cold is 11 litres per min

flow at 1st floor bath tap is 22 litres per min

flow top floor shower is 11 litres per min

As people have said you would expect 3 Bar and 20 litres per min on incoming main. Obviously inconsistency in readings between main and balanced flow rates. Would this be down to cylinder location and pressure flow rates at main or can anyone suggest an issue with how pipe work is run internally?

 

[John.g]

What is the (dynamic) mains pressure with 22 LPM on the first floor tap?.

Should also have asked what is the static mains pressure.

 

[ShaunCorbs]

Sorry but that doesn’t make sense you have 2 bar 7lpm incoming you can’t later have 22lpm out the 1st floor bath taps unless you have an accumulator fitted ?

 

[jimmy84]

Sorry but that doesn’t make sense you have 2 bar 7lpm incoming you can’t later have 22lpm out the 1st floor bath taps unless you have an accumulator fitted ?

It doesn’t make any sense. I would expect every where in the house to be the same. No accumulator fitted

 

[ShaunCorbs]

Where was the incoming flow rate taken ?

 

[John.g]

Maybe there's a PRV installed upstream of the PG because if not and both the taps where the flows were taken are similarly sized then it would require nearly 20 bar to increase the flow rate from 7 to 22 LPM. If one is 1/2" and the other 3/4" then if 2 bar is the dynamic pressure in both cases one might expect ~ 15 LPM from the bath tap?.