Double check valve query

[morg]

Hi, looking for some guidance on this please!

Having stripped the plumbing back to the 15mm copper incoming mains and now re-plumbing the whole house.

Intend to fit...
1. Pegler Lever Ball Valve (full bore)
2. Double Check Valve (wras approved)
3. Drain-Off cock

My incoming mains pipework is 15mm copper from the street. I assume fitting a 15mm DCV "does normally" reduce the flow rate?

My thinking is, I should fit a 22mm or 28mm DCV ? (if the 15mm DCV does indeed restrict the flow)

I know I should be measuring the incoming pressure / flow rate and I'll do this in a few days but in general do plumbers fit 22mm/28mm DCV or is 15mm DCV not really an issue?

Thanks for any help

 

[Madrab]

If you're worried about flow rates etc then you need to do something about that 15mm incoming main. You need to have a pretty good dynamic pressure to maintain a good flow rate through a 15mm pipe. You want that up to at least 25mm if possible. Do you know the pressure/flow rates? Y

Yes a 15mm DCV will restrict flow more than a 22/28mm.

 

[RandomGrinch]

1. Pegler Lever Ball Valve (full bore)
2. Double Check Valve (wras approved)
3. Drain-Off cock

My thinking is, I should fit a 22mm or 28mm DCV ? (if the 15mm DCV does indeed restrict the flow)

Only a DIY'er, but I've done exactly what you intend, when fitting an outside tap. Along with fitting a 22mm DCV on 15mm pipes, refining the pipe layout and using full bore valves, my flow rate improved by over 60%
...Although the main improvement could have been from getting rid of the self-cutting tap connector!
There certainly isn't any harm in fitting a larger DCV.

 

[morg]

Thanks both for the help much appreciated

I definitely cannot alter the incoming 15mm mains underground pipework (it is what it is no more digging ), happy to live with the output from that but obviously do not want to restrict the flow/pressure from this any further would be detrimental.

I think my best bet now is to fit the lever ball valve and do a flow/pressure test from that, then we can establish/test the DCV size/requirements


Cheers for the help

 

[Johntheo5]

If I'm reading this correctly then the pressure loss through this 15MM DCV is only 2.79M, 0.279 Bar, with 15mm (13.6mm ID) copper pipe which by my calculation has a velocity of 2.29M/sec at a flowrate of 20LPM.

132 Low Loss Double Check Valve c/w SU - Arrow Valves

Double Check Valves (ED device) with DZR brass valve bodies suitable for most pipe materials. Flat-faced connectors allow direct connection to the pipe without the need for sealants or additional adapters. Oversize, high-flow Cartridges provide exceptionally low head-loss characteristics. E.g...

www.arrowvalves.co.uk

A even better one, below, at a pressure loss of only 0.7M, 0.07 Bar.

https://www.hurlstoneassociates.co.uk/files/ed440datasheet.pdf

 

[Madrab]

Excellent figures from them - Must admit Arrow do have some excellent quality hardware. Not cheap though.

Only other thing I'd mention is any water velocity through a 15mm pipe greater than 2ms will start to get noisy.