Just out of interest, why don't the water co's now insist on new installations having NRVs fitted to the rising main near the stop c*ck, thereby covering the entire property. Presumably there must be a reason?
One aspect could be flow restriction, but the main one is that they are also concerned about contamination within the house.
I talked to one of the companies about this, and they gave me an example with respect to a shower. It appears that there are people who use the hose from a shower to "clean where the sun don't shine" as he put it, and then drop the hose into the toilet for cleaning.
If there were no check valve, it would be possible for siphoning to occur from the toilet to the downstairs tap.
There are scenarios where an outside tap could be backsiphoned into the internal supply as well, hence the protection is per risky outlet according to nature of the hazard.
If you contact the Water Regulations Advisory Scheme -
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- they will send you booklets on this stuff, and explain anything you want to know.
Rather than a kit, which will probably involve a self cutting connection into a supply pipe, better to buy the bits you need to do the job properly. The kits are only of limited use and depend upon a cold supply being just where it is needed and the self cutting fitting will restrict the flow.
Run as much of the new pipework as possible inside, preferably just have the tap alone on the outside wall so pipework is not subjected to possible frost damage. Otherwise make sure it is well insulated.
There are two ways to do it, one involves solderless pipe connections using olives and the other soldered connections. The latter are much cheaper and neater, but you will need a gas torch and a small amount of skill to do the joints.
There are two types of solder fittings, one which includes a ring of solder (solder ring) in the fittings and a type where you add the solder yourself.
Start work at the tap and finish with the T into the existing supply pipe. Clean all pipe ends and fittings internally carefully with a bit of wire wool, then add a bit of flux before attempting to solder.
Don't attempt to solder without first making sure that all water is drained out of the pipework in the area.
Correct. You could have the hose in the slimy fish pond and negative pressure occurs in the mains, then the slime will be drawn into the drinking supply. Also the dishwasher and washing machine may come on and the sink tap turned full on at the same time, then back siphoning into the house water supply.
Outside taps now come with the a double check valve integrated with the tap body. A simple job of just replacing the tap. They are quite cheap too.
it a piece of cake to get the tap threaded on tightly and vertical, & another cheap trick: using a washing machine tap to isolate the fitting coupled with a 3/4 > 15mm flexible pipe tail.
I *thought* some water authorities *required* a DCV and didn't like the tap mounted type very much?
I saw one of the "hosepipe pipe poked through the wall and jubilee clipped to the tap' type kits. After I pointed it out to them the owners got the 'plumber' back to fix the water that was spraying up the wall from the hose to tap fitting. He used some PTFE tape to give the hose a better fit ... oh and some Boss White ... nice ... (not)
I'd do the real thing for a bit more money (20 quid instead of a tenner, but a bit more work).
Ideally I need quite good flow as its going to be used for a hose pipe. My kitchen sing is directly under our back window and its there on the outside that I want the tap. So if I got a plumber in what would I be looking at for him to fit me a good tap and not one that screws into the kitchen pipework.? Thanks Simon
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