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Hi all, I'm planning on fitting my new sink which has a mixer tap. I'm using an unvented system, will this still require non-return valves fitted to the taps connections?
Discuss Non-return valves for mixer tap in the USA area at PlumbersForums.net
I'm using an unventedSorry, for some reason I read "vented" instead of "unvented" first time I looked and answered. With cold mains feeding the tap and also the unvented cylinder you should not need non-return valves.
The cold comes straight from the mains and the hot from the cylinder, the cold mains is at high pressure though. Would the pressure from the cold not cause backflow to the cylinder or is there usually a non return valve at the cylinder to prevent that?Edited -
Sorry, for some reason I read "vented" instead of "unvented" first time I looked and answered. With cold mains feeding the tap and also the unvented cylinder you should not need non-return valves. Unless you have very high pressure on the cold feed it should be fine.
I'm using an unvented
The cold comes straight from the mains and the hot from the cylinder, the cold mains is at high pressure though. Would the pressure from the cold not cause backflow to the cylinder or is there usually a non return valve at the cylinder to prevent that?
Yes, there's a non-return in the combination valve (aka "Group Inlet") which will not allow water to feed back to the cylinder no matter how unbalanced the pressures are in the hot and cold feeds.
The issue occurs when you have cold mains and gravity (tank fed) hot, the cold can overpower the flow of hot water inside the mixer tap (even then that depends upon the tap design and how the waterways are made) and feed back up to the header tank and cause it to overflow.
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