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Teeing off a 32mm MDPE mains water to run a small cottage.

Discussion in 'Plumbing and Central Heating' started by Rob Chavasse, 6 Mar 2021.

  1. Rob Chavasse

    Rob Chavasse

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    I am looking to reinstate a water supply into a small two bed cottage that is attached to my 4 bed house. There used to be an old shared lead supply that covered both properties. In 2008 they updated the main house to a new MDPE blue pipe, and left the cottage condemned and with no water supply.

    So my question is; can I tee onto the supply and will it have a detrimental effect on the main house? The cost of a new supply will be very scary as we are a bit remote. Please see the specs below:

    90m(!) x 32mm blue pipe from the nearest street, just before the house there's an adapter to switch it to a 25mm MDPE for the internal plumbing. This goes into a newly fitted combi boiler in the basement, which has to pump up to the first floor bathroom. From a quick test, flow rate = 15l per minute approx. Water pressure is fairly decent, but I will buy a test gauge if needed?

    I hope that is enough info, and any ideas or out the box thinking greatly appreciated! Thank you.
     
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  3. HERTS P&D

    HERTS P&D

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    What are your options, tee off your supply, run new supply from street or leave with no water?

    How far is the cottage from your property?

    Andy
     
  4. Rob Chavasse

    Rob Chavasse

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    Correct, tee off supply, run new supply or try and go off grid!
    Property is attached to main house, so pipe run from tee would be about 25m (have to go round a shed).
     
  5. HERTS P&D

    HERTS P&D

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    Ok, run a new supply tee'd off your water main, if the cottage pulls too much from your house then you know that a complete new supply would be needed from the street.

    But if the system worked before with your house and cottage sharing a lead pipe then I can't see any problems.

    Andy
     
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  6. Rob Chavasse

    Rob Chavasse

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    Involves a fair bit of work to do just as a test, digging to excavate, get plumber etc. But guess its maybe worth it for the potential it could save. Feel like it would be highly likely it would have a detrimental effect on the main house, but maybe I will give it a go...
     
  7. oldbutnotdead

    oldbutnotdead

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    Which tap did you get 15l/min from?
    You should be OK with teeing off, yes you'll have to dig a big hole in the ground but you can't go to the pub right now so why not.
    MDPE is very easy to work with- big compression fittings, minimal skill required. You could if you wanted to dig hole, connect new pipe, stick a tap on the end of the 25 metres or whatever, open that tap to give a flow of 15l/min then while that new tap is running,check flow/pressure in the house (and vice versa). If its good, then dig the trench from T to cottage.
    It might be wise to keep the T accessible (stoptap at the T for the cottage) so form a manhole at that point when you fill it in.
    Bear in mind if you get water board to run a new supply to cottage you'll get a new separate water rates bill and probably a new council tax bill for the cottage.
     
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  8. Ian H

    Ian H

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    You could also tee onto you 32mm and overland a temporary supply to the cottage and connect back onto its original internal stop tap to see how it goes.
     
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  9. Rob Chavasse

    Rob Chavasse

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    Perfect, thank you so much! That sounds like a feasible plan. The 15l/min is from my garden tap (near the main stop tap) and my kitchen tap (also near). Still a bit of a big job, but true, theres nothing else to do at the moment!
     
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  11. Rob Chavasse

    Rob Chavasse

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    So I will dig up and tee off the 32mm as close to the main flow source as possible.
    There will then be about a 25m run to the cottage.
    Should I lay 25mm or 32mm MDPE?
    The cottage will need less flow and pressure as its plumbing will all be at ground floor.
    So the choice should be what prioritises keeping better flow and pressure to the main house which needs to go from basement to first floor.
    Thank you for all the help!
     
  12. Nige F

    Nige F

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    25mm(y)
     
  13. oldbutnotdead

    oldbutnotdead

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    25mm. If you get any problems, stick a pressure reducer inline at the cottage end.
     
  14. Rob Chavasse

    Rob Chavasse

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    Amazing, thank you everyone for the help. Seems like its well worth giving it a go.
     
  15. HERTS P&D

    HERTS P&D

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  16. MeldrewsMate

    MeldrewsMate

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    You'll need a bigger hole too; enough space to get in and enough space to manipulate the 32mm pipe while you insert the new tee.
    Keep the hole clear of loose stuff too, stones and crap in the mains water can cause extra problems later.
     
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