Why 2 double check valves on filling loop

[Gary c]

Hi, I have recently had a water board inspection
This is what the report said about the filling loop on our press unit for a biomass boiler….

There is quickfill pipework directly between the mains water supply and heating supply. This type of temporary connection is permitted under the water supply regulations however the following must be incorporated:
1. Double check valve are required on both upstream (mains side) and downstream (heating side) of the braided temperate hose 2. Remove flexible braided hose when not in Use

I understand you need a double check valve and removing the braided hose when not in use, but why 2 check valves?

 

[Deleted member 120897]

It’s a new one on me. Perhaps ask the inspector?

 

[ShaunCorbs]

How many kw is the biomass ?

 

[Devisham]

https://wp.arrowvalves.co.uk//download/water-regs-tutorial-3-filling/

Information on fluid categories if it helps.

Probably gone for the 2 x double check to protect the mains supply and risk of backflow as much as possible without slapping you with an RPZ install notice as you could technically just connect to the downstream side from another source if it didn't have the backflow protection on that as well.

 

[ShaunCorbs]

https://wp.arrowvalves.co.uk//download/water-regs-tutorial-3-filling/

Information on fluid categories if it helps.

Probably gone for the 2 x double check to protect the mains supply and risk of backflow as much as possible without slapping you with an RPZ install notice as you could technically just connect to the downstream side from another source if it didn't have the backflow protection on that as well.

The same could be said for a dcv failing tho

 

[Devisham]

The same could be said for a dcv failing tho

True, there is always the risk with CAT 3, but if the water undertaker has instructed it to be installed as long as you've followed instructions you are covered.

Even CAT 4 RPZs fail and as long as they are repaired/replaced within the undertakers guidance time period you are covered. Only true backflow protection is CAT 5 to be honest.

 

[ShaunCorbs]

True, there is always the risk with CAT 3, but if the water undertaker has instructed it to be installed as long as you've followed instructions you are covered.

Even CAT 4 RPZs fail and as long as they are repaired/replaced within the undertakers guidance time period you are covered. Only true backflow protection is CAT 5 to be honest.

Another down side to rpz is the servicing