double check valve - noise & screw

[Nige F]

Could he not get rid of the non return entirely or am I missing sOmething.

replace with a single check . I`m not sure why doubles are used there I thought they were for wholesome water backflow protection - on hoses etc.

 

[gregd72002]

Could he not get rid of the non return entirely or am I missing sOmething.

replace with a single check . I`m not sure why doubles are used there I thought they were for wholesome water backflow protection - on hoses etc.

I don't think I will find a single valve of the same length as double one. And I do not want to cut/extend the pipes so I think I will stick to a new double valve... Though, got a bathroom renovation going on just now so this will have to wait for a few more days.

Anyway, thanks a lot for you answers everyone!

 

[Agile]

Whilst the test point can be used to drain the valve ( if fitted facing down ! ) the real point as Chris says is as a test point to comply with the water regulations in many applications when a double check is required.
DIA should have remembered that.

I would always fit a NRV on the hot OUTPUT from the boiler and not on the inlet. That can prevent damage within the boiler by expansion.

You can convert a double into a single by removing one plunger ( or by withdrawing its spring ).

Tony

 

[gregd72002]

[...]

I would always fit a NRV on the hot OUTPUT from the boiler and not on the inlet. That can prevent damage within the boiler by expansion.

[...]

I thought fitting NRV on OUTPUT from boiler is not recommended anymore therefore on the INPUT?

 

[Agile]

Why did you think that?

I will argue that it increases the likelyhood of damage inside the boiler!

Tony

 

[gregd72002]

I agree.. therefore the need for a mini expansion tank on DHW (that I do not actually have

To be honest, I do not remember just now where I found the recommendation on inlet NRV. But I agree it would make more sense to have it on the outlet, though I'm just an DIY person not a pro...

But, my boiler installation instruction do say that in some circumstances NRV might be required and it should be fitted on inlet... again, there is no justification of it

 

[Agile]

Most plumbers would fit it on the inlet.

But then most plumbers dont think about the technicalities ( or in many cases even have the basic scientific knowedge as they left school at 16 without taking/passing any science A levels ).

Tony