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New water supply pipe what size feed into boiler?

Discussion in 'Plumbing and Central Heating' started by JamesC1234, 7 Dec 2017.

  1. JamesC1234

    JamesC1234

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    Hi guys,

    Need a little help here and very new to all of this.

    We have a Victorian house and are struggling with low water flow, although pressure is ok. We want to have a decent thermostatic shower. Currently it is on a common supply pipe and we are house number 5 and it has a combi boiler. The (hopeful) solution we settled on was a new water supply pipe.

    A new 25mm MDPE pipe has been put in and is going to be connected to the water main. We thought it would be best to feed the new water supply into the boiler to deliver it the greatest flow rate.

    The plumber came this morning to fit the internal stop tap and make the connection into the house system.

    He has connected the 25mm supply pipe onto a 15mm copper pipe, which then runs to a T junction and splits into 2 x 15mm pipes, one which supplies the boiler and the other which supplies the rest of the house cold.

    Given that we want maximum water flow to the boiler and also to stop the problem with flushing toilets/taps/washing machine at the same time, should he have run 22mm pipe up to the T junction?

    Have attached a photo. Any advice greatly appreciated.
     

    Attached Files:

  2. muggles

    muggles

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    What make and model is your boiler please?
     
  3. JamesC1234

    JamesC1234

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    Worcester Greenstar 29CDi Classic
     
  4. JamesC1234

    JamesC1234

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    I have connected the new pipe and opened it up.

    New flow rate at the kitchen tap (i think it's the 1st tap) is 15l/min cold and 10l/min for hot.

    Definitely an improvement, but wasn't as fast or powerful as I was expected. The hot rate I understand is limited by the boiler, but the cold?

    Any thoughts? Decent enough to run a thermostatic shower?
     
  5. John D v2.0

    John D v2.0

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    Single Shower will be fine with 10l+ hot , the hard part will be getting it hot enough quick enough, 15mm short length is ok, it's the long distance that's the important bit.

    19mm id x long distance plus 12mm id x short distance is not much more than 19x slightly longer distance plus nothing.
    The 15mm tee probably provides more resistance then the short leg of 15mm pipe
     
  6. DIYnot Local

    DIYnot Local

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