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Water flow rate through pipes

  1. Sep 26, 2012 #1
    what is the water flow rate at an open 1/2" tap through 19mm diameter and 22mm diameter pipes at 4 bar pressure? I currently have 1/2" pipework and the delivery rate is terrible although I am told the incoming supply is from a 22mm pipe with 4 bar pressure.

    I am thinking of replacing the pipework to fittings with a larger diameter but the system includes a water filter with 19mm ports. I would be prepared to change this for one with 22mm ports or bigger if that helped.
  2. jcsd
  3. Sep 27, 2012 #2

    Andy Resnick

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    Does it help to remember that the hydrostatic pressure is equal to atmospheric pressure at the open end?
  4. Sep 27, 2012 #3


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    I would expect the flow rate to be fine unless there is a problem somewhere. Perhaps the pipes are scaled up? Perhaps there is a stopcock/valve not fully open?

    Perhaps a faulty pressure reducer? When we built our house we needed to add pressure reducers in the supply to some taps to stop water splashing everywhere. These worked fine when first installed but over a few years they reduced the flow rate to an unacceptable degree. At some point I will need to break into all the dry wall and adjust them. On the one I have done this worked fine and restored the flow to what it was originally.
  5. Sep 27, 2012 #4


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    Perhaps check there isn't a problem with that. I'd try bypassing it with a flexible hose or similar and see if the flow rate improves.
  6. Sep 28, 2012 #5
    Where is the water filter located? Is it right on the spigot? My daughter has a filter located on the spigot, and, in my opinion, the flow is too slow... but it doesn't bother her. Do you have other faucets in the house, and do they all run slow? What about the garden hose? What about the toilet tanks? Do they take a long time to fill? In other words, is the slow flow everywhere, or is it just in certain lines? Is it possible that tree roots are growing into your inlet line?
  7. Sep 29, 2012 #6
    Just a little off original topic.
    I have found (in Australia at least) when the first houses are being built in new suburbs, the water pressure from the mains is quite high so flow through the lines is high also, as the demand on the supply is low in the beginning. As more and more homes are built, the water pressure drops off as more demand is placed on the system. So over the course of the suburb being populated, the flow through the houses plumbing may drop off by 30-50% due to nothing more than demand catching up to supply.

  8. Sep 29, 2012 #7
    filters often get clogged and need to be cleaned or replaced....
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