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Running parallel water pipes from main

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  1. #1
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    Default Running parallel water pipes from main

    Quick question to the plumbers out there.

    If I run two 3/4" pipes from the main to a point at the back of my place, will I have more water pressure at a tap connected at the end of the two joined pipes?

    To make this clearer, if I make a T connection at the main, run two 3/4" pipes side by side and then join them together again at the end, will i have overall more pressure instead of a single pipe? Or is it better to run a whole new 1" pipe?

    Reason being, I need more water pressure at the back of my place and its cheaper for me to run another 3/4" pipe rather than a whole new 1" pipe.

    Dan.

  2. #2
    Tool Whore - 1K Club Member Vernonv's Avatar
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    I think you will end up with more flow with the same pressure.
    Cheers.

    Vernon.
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  3. #3
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    So will that alter your "litres per second" rate?

  4. #4
    That's SIR!!......Not CUR Ivan in Oz's Avatar
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    G'day Dan,

    You will have the same Water Pressure from either when you have the Tap turned off......No Flow

    As soon as you start to use water....( Litres per Second)
    You will start to get a reduced pressure.

    Less of a Reduction with the Second 3/4" Pipe.
    Me thinks 1" would result in a Smaller reduction,
    but ever so small difference you'd not notice.

    I liken it to Voltage Drop in a Conductor carring Electrical Current.
    Navvi

  5. #5
    Tool Whore - 1K Club Member Vernonv's Avatar
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    Assuming that the mains and the tap are not bottlenecks, then in theory you should get more litres per second, but at the same pressure as before.

    But practically, will your mains be able to supply twice as much water as it currently does? Will the tap be able to pass twice as much water as it currently does? I doubt it. But if there is spare capacity in both the mains and the tap then you should get an improvement in litres per second flow.
    Cheers.

    Vernon.
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  6. #6
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    Well, here's the deal, water from the front tap has loads of pressure, same type of tap at the back of the property, noticably less. The current 3/4" pipe length (with a couple of minor bends and slight elevation) is just under 20 metres distance. If I run a parallel, it would be the same distance.

  7. #7
    Tool Whore - 1K Club Member Vernonv's Avatar
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    Has the pipe been crushed? Or is it an old gal pipe that has corroded?

    It seems odd to me that you get good flow at one end but not the other.

    Are the front and back taps on the same "line" (i.e. are there separate branches for the front and back taps, or does the back tap line run directly from the front tap)?
    Does the pipe reduce diameter anywhere along it's run?
    Cheers.

    Vernon.
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  8. #8
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    You would be wasting your time and money, it wouldnt be worth the cost and hassle for little return. If the hose cock up the back is almost 20m from the one at the front you will have noticeably lower pressure as 20m is a fair run. There is quite a lot of friction that goes on between water and pipe, not to mention every bit of elevation and every change of direction and each fitting reduces it a little more on the way.
    You could try a 1/4 turn hose cock on the back one and see how that goes.
    Plumbers were around long before Jesus was a carpenter

  9. #9
    Diamond Member Barry_White's Avatar
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    I think you would find you would get better pressure with a 1" pipe because you will get less friction loss on the larger pipe but a better way would be to put an electric pump in the line up close to the tap with a pressure switch and pressure tank on it. This is what I have done to increase the pressure at all my garden taps as well as another one to the orchard.

    I have a 30 metre 12mm garden hose attached and it has increased the pressure dramatically.
    Regards Bazza

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    The views expressed by the poster are general in nature and any advice should be taken in this vein. The poster accepts no responsibility if this advice is used. When undertaking any work personal professional advice should be sought from suitably qualified persons in the field of work being undertaken.


  10. #10
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    What size is your water tapping in the street? I am just wondering if you will gain anything at all from either method if your tapping is only 3/4".

    Tools

  11. #11
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    To Tools - I'm pretty sure the the meter has a 1" fitting and then goes to 3/4" to the back of the property.

    To Vernonv - The 3/4" pipe does has a slight crush under the house about half way down. Its only minor but still has a crush in it. The back tap is 3/4" right through to the tap - there are branches off the 3/4" of course. It is becoming more apparent to me that the slight crush is the most probable reason for the pressure loss.

    To Wonderplumb - What is "a 1/4 turn hose cock"?

    To Barry_White - a pressure pump with tank will be my last option I think.

    Dan.

  12. #12
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    have a quick look in all the vanitys or dead spaces and see if there is another gate valve anywhere restricting the flow, we have valves on all our outlets prior to the tapwear to reduce the flow on everything except the shower. stops all the wasted water when you only get a trickle. (no sure what our visitors think though.sounds like the crushed pipe is the problem (easy to fix if you can get to it) just replace that piece a see how it goes.

  13. #13
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    In Melb area, it is also possible that you have a pressure limit valve inline between the meter/front tap (if fitted) and the house to avoid opening the pressure temp relief valve on the hot water system with raw mains pressure.

    Does the pressure within the house seem lower than that at the front tap, and similar to the back tap? If so, there would be a limiting valve installed before the house. Duplicating the run would effectively bypass the limit valve with the risk of having the pressure temp relief valve forced open, or rupturing hot water systems.

    If you have a PLV installed and need better pressure/flow at the back, you would be better to T off a new dedicated line before the PLV and run that to the back tap, completely issolated from the the house feed.

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