backflow protection

Hi, I had a new supply in when we were doing a renovation a few years back, and we also got them to put in a supply to a garden room that I'm only just finishing I have connected up the water but when i turn on the stopcock to the garden room it sounds like the water is back feeding into the...

We are refitting our bathroom and need a new shower - planning for a shower mixer with an overhead shower and a shower rail set, all concealed. Found the right combination but am stumped regarding the choice being offered of backflow protection being integrated into the shower mixer or not, so I...