15mm Double Check Valve (DZR) (WRAS Approved)

So, being a double check valve, whilst longer was still easy to fit after the isolator tap. It'll meets a standard that is well known and has minimal impact on the water pressure.So few household drinking water systems contain this device (at least in older properties), which is ok if your drinking water supply feeds only your drinking water, and to a larger degree ok if that same drinking water supplies certain appliances where there is good separation between the feed and the usage, it's even meh ok if that same drinking water supplies a cistern for toilet flushing that's enclosed, but my son wanted to install a bidet, and in none of the videos or instructions did they suggest or recommend a reverse check valve to prevent back flow.Backflow could potentially occur if during a flush, airborne particles of fecal matter or vomit (basically germs) land on the bidet jets, which can be 'pulled' back into the jets by the back pressure of a flush or a tap being turned on elsewhere, potentially even by your neighbours house or garden tap, but the risk there is lower, the higher risk occurs in the same house. So I instructed him on its purpose, the difference between a check valve (or non return valve) and more basic valves and isolation taps, and he was happy to wait for this to arrive rather than risk some nasty disease such as cholera.