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New 25mm mdpe, sizing stopcock

Discussion in 'Plumbing and Central Heating' started by martysmarty, 19 Jan 2021.

  1. martysmarty

    martysmarty

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    Looking for a lil advice!

    We had a new 25mm mdpe pipe installed with a bbox, this was tapped into the lead further up in our property so its still on a shared supply, although flow is much better!

    I just wanted to know, is there any point in swapping out to a 22mm 1/4 full bore valve vs a normal 15mm one? I only ask because the mains cold runs to the combi are going to be 15mm, this is tee'd off further in the house where the combi boiler is. The boiler and washer is in a utility cupboard 7 meters away from the incoming supply.

    What i was thinking was, 25mm mdpe to a 22mm stopcock under the sink, split the 22mm up into two 15mm feeds, one for the boiler/utility, the other for upstairs bathroom. Im not sure if i would gain much.... just thinking
     
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  3. Chris_W

    Chris_W

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    Usually a 15mm feed to combi is sufficient. It’s More the pressure and flow rates you need to worry about, discuss this with your installer.
     
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  4. JohnD

    JohnD

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    A larger stopcock does not constrict flow like a small one does, and may be quieter.

    I can't see any benefit in constricting a big pipe with a little valve.

    But bigger valves are more expensive.
     
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  5. Madrab

    Madrab

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    If your supply pressure and flow are good then reducing to 15mm shouldn't affect the supply that much.

    That being said, if you keep it to 22mm for as long as possible you will minimise any flow drop off when more than one outlet is open at the same time.
     
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  7. martysmarty

    martysmarty

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    Thanks both

    I would keep the boiler 15mm, infact id keep all runs 15mm. I was thinking more the fact of using 22mm to split into two seperate 15mm runs for up/down floors.

    Rather than using a single 15mm off the stopcock and splitting it 7 meters further down the line into two. Im probably over complicating it.

    Sorry madrab just seen your post as i wrote this, yes thats my theory on it
     
  8. TeaAndBiscuits

    TeaAndBiscuits

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    I don't think you're overthinking it - just paying attention to detail that will only cost marginally more to implement.

    When I replaced my little lead supply with the 25mm pipe and replumbed the house, I did the same thing. Comes into the house (in the utility/main shower room) then steps down to 22mm copper and a full bore lever valve. Then it goes to/from the water softener still in 22mm (with hiflow hoses and full bore bypass valves etc). After that it stays in 22mm as a sort of 'busbar' (to use an electrical metaphor) along the wall that everything else tees off from in 15mm. One pre-softener for the kitchen sink, one for the boiler, one for the shower, one for the washing machine, one for the toilet, one for the kitchen, one for the upstairs bathroom etc. Really just to try and help prevent the shower being affected by other cold outlets being used.

    Works really well - others can use cold outlets, flush toilets etc without noticing any difference in the shower.
     
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  9. martysmarty

    martysmarty

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    Thats exactly how i had it planned in my head, a busbar style. Its got to make a difference in my eyes

    Yea the cost is minor and as the mains is 25, thats why it come to mind. Thanks chaps im gonna go for it.
     
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  10. JohnD

    JohnD

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    mains 25mm is external diameter of plastic, so the same bore as copper 22mm, which has twice the capacity of 15mm.

    So one 22mm supply with two 15mm off it is IMO ideal.
     
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