Are backflow valves really necessary on pipes for a kitchen mixer tap?
I have ground floor standard mains cold water, a hot water tank on the first floor and a large cold water storage tank in the loft. Cold water pressure is 4 bar and hot water pressure at least 1 bar. I bought a Damixa Architect tap from B&Q which I was assured was suitable for my water supply but when I got it home, the info inside the box said not recommended for this type of water supply unless a backflow valve was inserted in both hot AND cold water supply pipes.
Are both really necessary and what's the reason for having them anyway if the cold water is high pressure?
Where about along the pipe should it the valve(s) be placed?
There already is a ball valve on the cold water pipe just inside the house, can this be used to control the pressure instead?
Also, are left hand flexibles available? I was hoping to use flexibles with the tap instead of the copper pipes supplied but turns out they are left hand threaded.
Sorry for all the questions, I'm tempted to either just put the thing in anyway and see or return the damn thing!