Help with return pump rating

Discussion in 'Pumps and Waterflow' started by mandarin, 2 Sep 2010.

  1. mandarin

    mandarin

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    I've got six tanks on a stand, three on each side, one above the other and a sump in the centre below.
    Each of the top tanks are 140ltrs and the sump 200ltrs.
    The highest point of the stand is 2100mm. The piping for the return is 25mm,there are 3 off 90 elbows on the return line and a T right at the top to fill the tanks left and right side.
    Each tank has a overflow pipe of 50mm with two way soil vent valve and reduced to 25mm into the next tank.
    I tried a 3000ltr/hr return but the pump can't do the job. Should i make the return line smaller or go for a bigger pump.
     
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  3. jacquesb

    jacquesb Retired Moderator

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    Hi Manderin - I have a similar sump tank system setup - I have the following:
    6 x 90cm tanks, of which they are built to act like 2 seperate systems. I "connected" the 2 systems, by placing a 2500 liter per hour cross-over return pump (just for this seperate "system") in each bottom most tank (the "sump" of each "system"), which pumps water across to the opposite top most tank, that I have a "cross-over effect"..... This ensures that the water circulates between my 2 "systems"...

    Now - for my return pump, I am using a 2500 liter per hour pump, which has a head of 4 meters....... I have to actually even tune this down, because due to my overflow outlet pipe of my DT that goes DIRECTLY into my skimmer - and due to the tuning of my skimmer and the amount of water that comes out of the outlet of my skimmer and goes into my sump tanks system.
     
  4. chikaboo

    chikaboo

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    The water is going to look for the easiest "route" out so if you put ball valves on the lower tanks you can "close" off the return to those slightly to "force" the water up higher to the other tanks .... besides the "litres per hour" hows the "head height" rated on the return pump?
     
  5. mandarin

    mandarin Thread Starter

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    The head height is rated at 2.5mtrs but when the pump switches on it takes to long before the water gets to the top. Wouldn't it be better if i can make the return line 20mm or replace it with a clear flex pipe then there will be no elbows just one T split at the top. At the moment the sump level is to low.
     
  6. AfricaOffroad

    AfricaOffroad

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    A smaller 20mm line will increase the frictional losses in the line and reduce the flow even further.

    Ball valves are very hard to use for balancing the flow to the various systems (each with their own frictional losses - head loss on pump). You could try using gate or spindle valves to get better modulation.

    It also sounds like your pump does not have sufficient capacity, particularly its nett pumping head of 2.5m (at which you will get no flow). I'd go with a bigger, better rated pump as a starting point.
     
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