non return valve on incoming main?

[Readingplumber]

Is it compulsory to have a non return valve at entry of property after main stop valve?

Also why is it wrong to use a lever valve (one that works on mains) in the place of a stopvalve to a dwelling?

Thanks again folks look forward to your replys!!

 

[W.T.Pearce & Co]

Also most lever valves are not classed as serviceable; in my opinion don’t scrimp on this part of your system. That humble stopcock might just prevent allot of property damage if you have a burst etc. As in a hurry you do not want to find out the stop cocks not shutting then sods law your water box is full of rubbish. Then you’re in deep do.

As for backflow prevention, all potential causes must be fitted with suitable check valves immediately upstream. Main culprits are your cheapo hose union bib taps with no built in checks and old washing machines etc.

Don’t forget to put a drain off straight after your stopcock too, plumbers working on your system in the future will thank you no end.

 

[justlead1]

Hi. Stop cocks have an arrow stamped on showing the direction of flow. If fitted the wrong way round no flow as it becomes a non return valve. Good luck

 

[dorset]

In a word no!

 

[Mike Jackson]

Depends on the property. If it is a flat on a shared rising main all but the lowermost flat require a double check valve. Properties with an individual main do not require one at the entry but do require appropriate backflow prevention elsewhere within the property.

The rule on having to a stop tap as the main isolator has been changed to allow approved full bore lever valves.

Th

 

[Bernie2]

The loose jumper in a mains water stop tap acts as a non return valve as justlead1 said. Backflow prevention devices are best understood when you realise they are there to prevent water back-flowing down the mains water pipe and contaminating the local water supply. How?

Well if you ever go to a job with a suspected underground mains burst on the property, get a clean jug and fill it to the brim with clean drinking water. Then turn the main stopcock off in the street, run in and turn on the sink unit cold tap and stick the nose of the top into the jug of water. What happens is that the water gets sucked out of the jug back down the mains water supply. Its quite spectacular to watch and an old trick to make sure you do have an underground burst on the property.

But imagine instead of clean water you had a garden tap with a hose on it, whose end had been stuck in a puddle of water run off from a garden manure heap, or a shower hose in a bath of dirty clothes water or old style basin taps instead of raised nose keeping the nose higher than the basin spill over level.
The water would be sucked back down the main and possibly come out next time the main was turned on, if it did not drain away through the burst, anyway the main would be lined with liquid manure.
That's why you flush mains after repairs and check ball valves and why you make sure you fit double check valves where the Regs tell you too. I'm talking from the point of having seen it all happen.

 

[Oxfordplumber]

f you look i water regs and BS6700, shared occupancy or domestic properties shariing same supply require double check vales. ALSO screw down stop valve is recommended such that the pressure comes onto the system slowly, if you turned a lever valve on with 5 or 6 bar on it ( happens in witney) you would hav efittings and shower valve conrrols firing off like rockets. Water regs and BS 6700 also lists valves which are suitable for underground and concealed use. Not enough people actually read thse documents.