Good mains pressure, poor flow, new 32mm MDPE connection

[belfastbob]

Hi guys

I have a new house which is connected to the water main with about 20m of 32mm MDPE (26mm i/d). Measured at the internal stop tap, I have decent mains static pressure of 3 bar. When I turn on a tap, the dynamic measurement is a different matter altogether.

I monitored the dynamic pressure just after the internal stopcock, adjusting the flow through it using the outside tap. Here are my results.

Pressure [bar], Flow [ltr/min]
3.0, 0.0,
2.7, 5.1,
2.4, 6.0,
2.0, 7.8,
1.7, 8.9,
1.3, 10.5,
1.0, 11.9,
0.4, 13.6,

The water is only flowing from the main, through the external stopcock, down 20m of 32mm MDPE, though the internal stopcock and out the outside tap.

In all cases, the pressure drop at that flow rate is equivalent to over 2000m of 32mm MDPE (confirmed using www dot pressure-drop dot com). I've only got about 20m to the main supply so I can't understand where the restriction is. If the pipe is new and installed correctly I should see virtually no pressure drop across it at these flow rates. The only thing left in the path is the stop cocks. A stopcock wouldn't drop 1 bar at only 7.8 litres per minute would it?

Your advice is much appreciated.

Bob

 

[Paulus]

It could be a dodgy stopcock not opening properly or debris inside.

 

[Killy Bing]

or a restriction before your take off from the mains

 

[albatross]

First thing is get the water board to come and do some tests.

Blockage/airlock/faulty valve or meter.

 

[Killy Bing]

Non return in the meter could be playing games too

 

[belfastbob]

Believe it or not, in N. Ireland we don't have water meters!