I have the choice of a bi-flow mixer tap or mixer tap. Which one has the possibility of back flow problems and why? Trying to learn some plumbing, also want to know which one is more reliable.
If a mixer tap allows clean mains cold water to potentially be contaminated with stored hot water, it doesn't comply with the Water Regulations, so you shouldn't be fitting it in any circumstances. If the tap allows hot and cold water to mix inside it before they reach the end of the spout, the higher pressure mains cold water could force its way back into the hot water pipework. And, vice versa if the hot water is high pressure and the mains low. That's the non-WR compliant bit. As to reliability, they're nearly all made in some little chap's shed in the depths of China, so it's pot luck if his glasses had steamed up while he was making it or not. Cynical, me?! I've got on well with Reginox taps recently, and although Bristan do some good ones, I've had some problems (dripping from new) with their ones that fit from above the sink. I've also had some really basic ones from Screwfix that are great, and fitted exactly the same one for a different customer and had to take them back, so I'm afraid typical reliability is very difficult to determine. Perhaps not much help, but I hope it's of interest.