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15 or 22mm for my Cold Mains? Water loop?

Discussion in 'Plumbing and Central Heating' started by mstizomad, 3 Feb 2017.

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  1. mstizomad

    mstizomad

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    Hi,

    I have just plumbed all of the Cold Water for my house.

    I have put in a new 15mm stop cock, pressure reducing valve, drain cock and then 15mm copper pipe with soldered joints to my Kitchen and then to my bathroom.

    I have done it ALL in 15mm, including up to the Bath taps etc.

    The reason why i did it all in 15mm is because the external and internal stop cocks are both 15mm and i didn't think that increasing the bore after these bottle necks would make any difference.

    Was this a mistake? Would i have been better off going up to 22mm after the stop cock and then only going down to 15mm again for kitchen sink etc, but keeping 22mm right up to the Bath?

    The house is still fairly ripped out at the moment, so i am happy to re do a large section of the pipework in 22mm copper if if you think it will improve flow rate. But the stop cock will always be 15mm.

    We are currently getting a flow rate on the bath cold of approx 12 litres/min on 15mm.

    However i have used 300mm long 8mm bore flexi hoses on the bath, which i plan to rip out and redo all in solid copper pipe right to the tap as i think these are restricting flow. I recon the flow on the bath might increase to 15 litres / min once i change the flexi hoses to solid copper.

    Also, another crazy idea. Would there be any benefit in making my water main pipework into a loop, so the end feed back to the stop cock again. Almost like a ring main, everything being fed from two sides. Would this increase flow rate or help to prevent pressure drops when two water items are use at once such as Toilet and Shower?

    Any thoughts?

    Thanks
     
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  3. mstizomad

    mstizomad

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    Here's my very basic diagram of my house. The blue lines are the existing cold mains in 15mm copper.

    Is it worth adding more pipework (purple) in order to create a loop? or is this pointless?

    water.jpg
     
  4. muggles

    muggles

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    The loop won't help at all. Personally I'd have done it in 22mm to future-proof it in case you decide in the future to have your incoming main upgraded, but if you don't think that's likely to happen the 15mm should be fine
     
  5. mstizomad

    mstizomad

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    Hi, thanks for your reply. Fair enough, i thought that it might not help.

    Is 12 litres/min a poor flow rate for a bath?

    That's my biggest concern currently.
     
  6. muggles

    muggles

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    A bath holds about 80 litres with a person in it, so that's about 7 minutes to fill up. Whether that's OK or not depends on how patient you are!
     
  7. fezster

    fezster

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    Can you test your mains at the stop cock? If your incoming supply flow rate is significantly more than 12 l/min, then you'd benefit from upgrading the pipework to your outlets.

    Something I struggled to get to grips with, until I did it myself - my unvented cylinder had 22mm inlet/outlet, but I had the pipework either side upgraded to 28mm which provided a significant boost in flow rate. It's the overall resistance of the pipework which matters.
     
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  8. mstizomad

    mstizomad

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    Hi guys,

    I have just removed the old standard Isolation Valve (narrow bore) and replaced with a Full Bore Isolation Valve and the full bore Stainless steel / Copper flexiblle pipe and it has made a MASSIVE difference to the flow rate for the bath.

    Before i measured it at 12 litres/min using a stop watch and a 1 litre jug. Now it's consistantly measuring between 25-30 litres/min.

    Cheers!
     
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