Check Valves

[flyingsparks]

I am currently reading a level 2 plumbing text book as I am keen to learn more about plumbing. As far as I can see you should have a single check valve on each leg going to a mixer tap. 2 questions.. I live in a 3 year old house and cant see any check valves before the mixer taps in my house? And also, I have seen techniques to clear air locks by holding a cloth over the tap and forcing mains pressure cold back the hot pipe. I guess this wouldnt work if check valves are fitted? Thanks. Chris

 

[Whitespirit66]

It's always good practice to put isolation valves on supplies near a tap. No requirement to put check valves though.

Check valves can also impede the flow on gravity supplies.

Yes, you're right about not being able to clear locks on gravity supplies, if check valves were in place.

 

[OLLIE20]

Yes it is good practice to do this, and no you wouldnt be able to clear the air lock that way from a tap with check valves on

 

[xr4x4]

Check valves should always be fitted to the cold supply where risk of waste water can be drawn back into the cold supply.

Ie, a mixer shower tap attachment over a bath, where the shower head could be left in dirty bath water.

I thought it was a water regulation?

 

[seco services]

I thought it was a water regulation?

It is.

 

[OLLIE20]

Also if your mixer passes, it can run back up into cold water tank and cause it to overflow

 

[xr4x4]

I thought it was a water regulation?

It is.

Only in certain circumstances?

Could you clarify?

 

[seco services]

What do you mean in certain circumstances ?
Either the showerhead reaches below the bath overspill or it don't.
ie 25mm min from overspill or below 25mm requires a double check valve.

Page 6.38-39 in water regs book.