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    • CommentAuthorRex
    • CommentTimeMar 31st 2018
     
    What ho gentlemen,

    This is more of an academic question. But first some background.

    Prior to moving into our house, we were in a small maisonette with water supplied from a loft tank. Of course, the kitchen was mains. Although the pressure / flow was not great, I don't recall there being any noticeable reduction in pressure or flow when two taps were open.

    The new house is mains pressure throughout. To ensure good pressure, I put 32mm from the mains, reducing to 22mm throughout the house. Of course, it reduces to 15mm to the taps, and that is frankly a joke because the internal bore to the flexible tails for mixer taps is probably closer to 12mm (or less!)

    The mains pressure is 5 bar, reduced to 3 since that is the advised pressure for the water softener.

    With any one tap open, there is good flow and pressure, but open another tap anywhere in the house, and pressure / flow drops noticeably

    Is it too late to do anything now, but what does one normally do to ensure good flow / pressure when more than one tap is open when building? Did I do something wrong?

    I have to admit that it is one of my disappointments with the house.

    Thanks and toodle pip
    • CommentAuthorArtiglio
    • CommentTimeMar 31st 2018
     
    If your filter has a straight through bypass does the flow rate still behave the same using the bypass, does it improve if you increase pressure through the bypass. Have you checked the flow rate before it enters the reducing valve? Could be you have 5bar static pressure from the mains but a low flow rate. If however mains supply is good, matter of working downstream until you find which point is choking the flow.
    • CommentAuthorRex
    • CommentTimeMar 31st 2018
     
    Yes, the water softener does have a by-pass so I could test by taking that off-line.

    The pressure was tested when the plumber was installing the boiler and cylinder. he just put his gadget onto the outside tap so I guess that was a static test. I don't think there is a flow rate problem but how would I check that?
    • CommentAuthorArtiglio
    • CommentTimeMar 31st 2018
     
    In which case i’d check the flow rate, big container of known volume , stop watch and tap wide open. If that is poor, then do it again upstream of the flow regulator.
    If mains supply is good, prime suspects will be, regulator, filter and anything with a non return valve in it.
    Sounds daft , but check meter/stopcock is fully open. Sometimes its the simplest thing.
    •  
      CommentAuthordjh
    • CommentTimeMar 31st 2018
     
    Posted By: RexOf course, it reduces to 15mm to the taps, and that is frankly a joke because the internal bore to the flexible tails for mixer taps is probably closer to 12mm (or less!)

    Not a joke really. The pressure loss depends on the total length at a given diameter, so a short tail of smaller diameter won't have much effect.

    Nothing to add to Phil's suggestions for diagnosing the problem. If it is a flowrate problem, then adding an accumulator might fix it, but let's wait to hear the results of your tests first.
  1.  
    Just fit a shower pump that will pressurize all your hot and cold water.
    •  
      CommentAuthordjh
    • CommentTimeApr 2nd 2018
     
    Posted By: renewablejohnJust fit a shower pump that will pressurize all your hot and cold water.

    Won't help if it's a flowrate problem.
  2.  
    Posted By: djh
    Posted By: renewablejohnJust fit a shower pump that will pressurize all your hot and cold water.

    Won't help if it's a flowrate problem.


    Of course it will the pump will just compensate for any drop in pressure for the tap that is open.
    • CommentAuthorArtiglio
    • CommentTimeApr 2nd 2018
     
    But in the OP , it says there is a pressure reducing valve already dropping pressure from 5 to 3 bar, so when taps are open the regulator should be maintaining the 3 bar, if it is then it suggests that there is a flow restriction after the regulator ( filter/ softener being a good place to start) in which case there is insufficient volume to maintain pressure with open taps.
    If lack of flow from the mains is the underlying problem, then as suggested previously an accumulator (or pumped storage) may be required, but thats not a solution i’d personally jump to without checking existing instsllation carefully.
  3.  
    Posted By: ArtiglioBut in the OP , it says there is a pressure reducing valve already dropping pressure from 5 to 3 bar, so when taps are open the regulator should be maintaining the 3 bar, if it is then it suggests that there is a flow restriction after the regulator ( filter/ softener being a good place to start) in which case there is insufficient volume to maintain pressure with open taps.
    If lack of flow from the mains is the underlying problem, then as suggested previously an accumulator (or pumped storage) may be required, but thats not a solution i’d personally jump to without checking existing instsllation carefully.


    I just assumed the water softener was the restriction so you need a pumped supply from a holding tank after the softener to maintain the 3 bar pressure.
  4.  
    The PRV is probably too small. It sounds like you have a restriction somewhere in the system - A 32mm incomer is a good size, so I'd look elsewhere. My money is on either the the PRV or the softener.

    What I'd do is some measurements.
    Hot and Cold, Kitchen, Bathroom, One open, both open, and see where you stand.
    • CommentAuthorbxman
    • CommentTimeApr 2nd 2018
     
    Could be as simple as the main stop cock not being fully open it will give you the full pressure until such time as you want a decent flow .
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 2nd 2018
     
    Posted By: renewablejohnJust fit a shower pump that will pressurize all your hot and cold water.
    Are you allowed to add a pump to mains water?
    I know someone that fitted a shower pump to a mains pressure system, lasted about half an hour before to burst open.

    http://www.pressure-drop.com/Online-Calculator/

    Then there is dynamic pressure to take into account.

    https://www.engineeringtoolbox.com/dynamic-pressure-d_1037.html
  5.  
    Posted By: SteamyTea
    Posted By: renewablejohnJust fit a shower pump that will pressurize all your hot and cold water.
    Are you allowed to add a pump to mains water?
    I know someone that fitted a shower pump to a mains pressure system, lasted about half an hour before to burst open.

    http://www.pressure-drop.com/Online-Calculator/

    Then there is dynamic pressure to take into account.

    https://www.engineeringtoolbox.com/dynamic-pressure-d_1037.html


    If they where not legal then I cannot see screwfix selling many of them. Personally dont have the problem as we are off the mains.
  6.  
    I thought shower pumps were normally fitted to systems where there was a cold water tank in the loft which fed DHW and the shower pump was/is used to increase this normally low pressure.

    I also thought that fitting pumps to the mains was not allowed because this could cause suction in the mains pipe which could cause problems to other users and could also suck in contamination through any small faults in the pipe that would otherwise be minor leaks under the normal mains pressure.

    IMO Rex should be doing a flow test as suggested above with the PRV and the water softener as first candidates and eventually ding a flow test at the stopcock if no other faults are found and then talk to the water co.. (BTW what does the spec. of the softener say about through put or flow). And I also thought that it was not recommended to have a water softener on the drinking water tap - perhaps someone could advise.
    • CommentAuthortony
    • CommentTimeApr 3rd 2018
     
    Do not drink artificially softened water, very bad as high in sodium and can cause heart problems or worse if heart problems already exist.
  7.  
    "Do not drink artificially softened water, very bad as high in sodium and can cause heart problems or worse if heart problems already exist."

    False.
    • CommentAuthortony
    • CommentTimeApr 3rd 2018 edited
     
    Wot! High sodium intake is dangerous medically for lots of reasons.

    https://en.m.wikipedia.org/wiki/Health_effects_of_salt
    • CommentAuthorgoodevans
    • CommentTimeApr 3rd 2018
     
    As I understand it softened water will have a little extra salt in it - the question is how much salt per litre and how much is drunk. So yes, excess salt is not good for your health, but will softened water be responsible for that excess or is it other sources such as takeaways.

    Each water softening system will leave a different level of salt in the water - and If I get one I will also get a salinity tester (from ebay) to double check should I use that water and not fresh.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 3rd 2018
     
    Posted By: renewablejohnIf they where not legal then I cannot see screwfix selling many of them.
    They are sold for use with vented systems and, rightly or wrongly, assumed to be fitted by people that know what they are doing.
  8.  
    >Wot! High sodium intake is dangerous medically for lots of reasons.

    Sure, but a water softener should not be adding any significant amount of sodium to your diet.

    http://www.problemwater.com/s_softeners.html

    It still makes sense to have a drinking water tap in the kitchen (or just to run the kitchen cold tap unsoftened) but it's not strictly necessary unless you have a specific sodium intolerence.
    • CommentAuthorgoodevans
    • CommentTimeApr 3rd 2018
     
    Back to the op's issue - do you have an outside tap (or any tap) before the PRV. If so it's another 'experiment' point to try. Let us know the results of your testing.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 5th 2018
     
    Softened water is basically calcium/magnesium free and as a strong solvent (that's why we use water for cleaning etc) will hungrily scavenge those minerals from wherever, incl the body incl the bones - osteoporosis - nice!
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