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Thread: Water pipe friction

  1. #1

    Water pipe friction

    What would be the pressure increase due to pipe friction on

    A) 950 metres of 32mm pipe 35litres/min flow.

    B) 950 metres of 50mm pipe 35litres/min flow.

  2. #2
    Slurry Solutions

    Re: Water pipe friction

    Making a couple of assumptions here -

    pipe sizes are mdpe, therefore OD rather than ID
    32mm MDPE = 25mm ID
    50mm MDPE = 40mm ID
    Also assuming clean water

    25mm ID at 35lt/min losses are 9 m head per 100m pipe therefore 85.5m loss over 950m

    40mm ID at 35lt/min losses are 1m per 100m pipe run therefore 9.5m loss over 950m

    These figures are based on internally smooth cast iron pipe, they can be reduced by 45% for smooth pvc / plastic although I tend to use the cast pipe figures as this gives you a reasonable allowance for bends, valves tees etc.

    As you can see the extra pipe diameter makes a vast difference, and well worth the extra expense in most cases.

    Regards, and hope this helps


  3. #3

    Re: Water pipe friction

    Do not forget there will also be terminal pressure losses through any lift in the pipe

  4. #4

    Re: Water pipe friction

    I have just got into the realms of this , a few weeks ago .
    Installed a seperator , and utilised the old dirty water Alcon pump to pump dirty water off 450 meters to a collection pit .
    Pit is actually lower than the pump (which also has the luxury from drawing from a 3300 gallon storage tank that is above it !
    We installled a 63 ml mdpe pipe (56-57 internal ) and I even thought it might trickle by gravity
    The rub is ,that the pipe goes down hill for 325 meters and than gradually uphill for 125 meters ! If it was downhill all the way it would be a lot easier for it .
    So ,we have about 500- 600 gallons an hour max at the present .
    Not really sure about bigger expensive pumps ,as I have been told they wont make an awful amount of difference!

    950 meters is a long way for 32 ml pipe unless its all downhill??

  5. #5

    Re: Water pipe friction

    Thanks for the replies. Yes it is MDPE pipe.

    It is also lifting 85 metres

    Pump pumps 35 litres a minute to a maximum of 185 metres.

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