Isolating Valves

[Unregistered]

Do isolating valves prevent water backflow.

 

[ajs heating]

no a check valve does that

 

[ProffesorPlumb]

There are different backflow prevention devices for different scenarios.

Water Regulations are very strict on where these are installed. It is a legal offence to not use the correct backflow prevention on a system if its needed.

 

[SteveO]

NO. A single or double check valve will do this as per the water regs.

 

[sibs]

In what circumstances would you need either a single or double check valve to prevent backflow?

 

[chawkey@hotmail]

depends on what fluid category you are dealing with, outside taps you should use a double check valve as a hose pipe could be connected to it and so increase the risk of backsiphonage. There are all also RPZ's which are used for zone protection mainly in comercial premmesis, but for domestic best to use a double check valve if in doubt

 

[bcp]

In what circumstances would you need either a single or double check valve to prevent backflow?

Buy the current water regs book. If you are in the arena where regs compliance is part of your daily grind, then it is invaluable. From a business perspective, a job quote is often made higher by the requirement to install specific valves/bits/methods in order to comply. Many cowboys ignore this, so the 'proper' plumber is at a disadvantage. If you show the customer the relevent paragraphs in the regs book, I have found this often (sadly not always) overcomes the price objection.

 

[Winston]

Always have a copy of my water regs in my van and a copy on my desk. I always have a look prior to a job that I havent done before or as a reminder.

 

[paulproject]

single check valves are acceptable for use with fluid category 2 risks eg where mixing of hot and cold water supplies occurs, domestic softening plant, drink vending machine, fire sprinkling systems (without anti-freeze), ice making machines.

double check valves would protect against fluid category 3 risks eg water in primary circuits and heating systems, domestic wash basins, baths and showers, domestic clothes and dish washing machines, domestic hand held hoses with flow controlled spray or shut off control, hand help fertlizer sprays for use in domestic gardens

hope this helps

 

[HTB]

bcp is bang on re: being priced out by Mickey Mouse cowboys.

 

[Bernie2]

Some of the cold screw down stop taps where intended to act like a none return valve by having loose washer jumpers.

The water entered through the seating by pushing the jumper up in the air any backflow is supposed to force it back down onto the seating stopping backflow into the main water.

Many screwed down main water stop cocks still use the same principle today, but they are not classed as none return valves.

Incidentally you can find them on some old bath taps as well. You usually find out when you nearly blow your brains out blowing against a closed valve when your trying to clear air locks, or the hose jumps off when you try to force water down the pipe to clear air locks.

They can also be found on some main storage cisterns preventing you blowing air out of the pipes into the cistern also to clear air locks.