double check valve

[plumdum]

i know a check valve is a one way valve which has a ball bearing in it.
but what is a double check valve?

 

[justlead1]

Hi. Some do. Double check is two single joined together but to make it easy they manufacture as one fitting

 

[plumdum]

so a double check valve is a valve with two one-way valves.
isn't this a bit overkill.
where would you install this instead of a single check valve?

 

[Alanc]

Regulations vary between England/Wales/Scotland/NI, for example the Scottish regulations always seem to say "A double check valve" should be fitted.

Al

 

[djmbristol]

so a double check valve is a valve with two one-way valves.
isn't this a bit overkill.
where would you install this instead of a single check valve?

a shower

 

[Alanka]

A bath or washbasin tap (domestic) with a submerged inlet or inadequate air gap;

a garden tap to which hose connection can be made;

a flexible hose with spray or jet that can reach a basin, bath, or shower tray (Category 3 risk).

All these situations would need double checkvalves fitted to comply with the Regs.

 

[fuzzy]

so a double check valve is a valve with two one-way valves.
isn't this a bit overkill.
where would you install this instead of a single check valve?

depends on the risk.
its not just two singles but locks water in the middle of the two one ways which coul re enter th mains water system with a single

there are more sophisticated non returns than a double check valve such as an RPZ valve, used on cat 4 if i recall correctly