Double Check Valve on incoming mains

[Stefromthewirral]

Hi all,
I have two questions that I'm looking for advice on please?
1. I've been asked to fit a double check valve on a new incoming main. I only did my water regs last year and this wasn't stipulated in the reg's? Has this now changed or did miss something? The property in Cheshire. The main's has been signed off without it by the waterboard.
2. Also if the owner pushes to have it fitted, my concern is that fitting this may cause a drop in the flowrate? Does anyone know how much a 22mm double check valve will potentially reduce the flow?
Thanks

 

[Aire]

Its my understanding that double check valves are only required on the main when there is a risk of backflow e.g. a block of flats. Who's asking you to fit it? If it's the customer just tell them it's not legally required but if they push for it tell them it will have an impact on the flow rate and that it's chargeable if they then want it removing.

 

[Dan1990]

Fitting a double check valve on the incoming main will not prevent contamination of drinking water within the property. They will still need to be fitted on outlets where required.

Are sure the customer has not confused double check valve with pressure reducing valve?

 

[centralheatking]

Hi all,
I have two questions that I'm looking for advice on please?
1. I've been asked to fit a double check valve on a new incoming main. I only did my water regs last year and this wasn't stipulated in the reg's? Has this now changed or did miss something? The property in Cheshire. The main's has been signed off without it by the waterboard.
2. Also if the owner pushes to have it fitted, my concern is that fitting this may cause a drop in the flowrate? Does anyone know how much a 22mm double check valve will potentially reduce the flow?
Thanks

Double check valves ...the regs are quite clear...purpose to prevent contamination of the mains water supply as a result of back flow from 'dirty' water supply connected usually
semi permenantly to the mains water. like. hose pipes, pressurised heating systems, and a whole host of commercial applications, and in high rise and flats. There is NO need to put one on the mains input to the property. Take the high ground and inform the customer
its also a question of where you put it and what happens when it eventually fails
centralheatking. however if this property is at the bottom of a hill with properties higher up...then just like a block of flats I can see the logic ....almost ..chking

 

[Stefromthewirral]

Its my understanding that double check valves are only required on the main when there is a risk of backflow e.g. a block of flats. Who's asking you to fit it? If it's the customer just tell them it's not legally required but if they push for it tell them it will have an impact on the flow rate and that it's chargeable if they then want it removing.

Thanks for the reply, i thought the same, the builders asked the customer to get me to do it. However he has said that the gas guy who is fitting the boiler always fits them on all his installations and requested it. But strangely enough though the same builder has said that he usually does all his cold feeds on domestic installations in 22 instead of 15 as he finds it's got better flow? And then drops them to 15 to the outlets

 

[Stigster]

Backflow prevention in this country at least is always done at the point of use and not the point of entry to the building for reasons already mentioned. A check valve on the incoming mains protects the system outside the house but does nothing for anything inside the property.

Fortunately decent manufacturers and installers alike take backflow prevention seriously and tend to follow the regulations (Handheld bidet manufacturers excepted) and by preventing backflow at point of use takes care of the whole system and makes check valves on the incoming main largely redundant and wholly redundant in a domestic setting.

I wonder what those that feel it's a good idea to put it on the incoming main are thinking? Are they admitting their system could be non-compliant and such a thing is required? I doubt that so what is the thinking behind it? It doesn't protect you from anyone else's mistake on the network either?

 

[centralheatking]

Thanks for the reply, i thought the same, the builders asked the customer to get me to do it. However he has said that the gas guy who is fitting the boiler always fits them on all his installations and requested it. But strangely enough though the same builder has said that he usually does all his cold feeds on domestic installations in 22 instead of 15 as he finds it's got better flow? And then drops them to 15 to the outlets

Oh great here we go again, a builder procrastinating about plumbing matters. Not good
thats why there are qualified trades ...gas, plumbing electricity ANYBODY can be a builder
obviously the builder knows better thats why you are on here asking experienced engineers.....centralheatking

 

[Stefromthewirral]

Thanks guys for all your help, it's just a bit of a awkward situation as i am presuming the boiler fitter is a qualified plumber like myself? If he is going back to the builder, who is going back to the client, I just needed a bit of clarity from some other qualified tradesmen, because I knew this wasn't right, but the builder was adamant.

But I won't be fitting it and I will check the pressure and flow after I've commissioned the system, just incase it gets fitted after I have left and there is a drop in the flow rate or pressure resulting from this.


Thanks again

 

[ShaunCorbs]

You could install a swing check valve must be installed horizontally this wouldn’t cut down on the flow as it’s nearly full bore