Hi there.
Fresh over from Electricians forum..
I built an extension. My old boiler (1970’s, half gravity, in-wall vertical sectional concrete flue) - has all gone.
75% re-do of the rads and plumbing underway.
New boiler location will be on the outside wall of extension which is now ~6M from the original boiler. HW tank and feed from loft tanks are vertically above the original boiler location.
My best bet I believe is to stick with an open vent boiler. The vent, inlet, pump, valves (S plan +) and distribution manifolds will be in the location of the old boiler. The expansion pipe and feed can run vertically up from this location.
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The new boiler flow and return (22mm) will both need to take an inverted loop then a "uninverted" loop from the new build outside wall, beneath the new floor then above a ceiling to come out at the proposed location of the vent/inlet/pump. Horizontally this is about 6M, pipe length probably 9M. Should I expect any problems with this distance? I am assuming it would be essential to add some T pieces and air valves near the boiler for example, and the high points, also drain cocks, but this leads to two little questions:
If I decided instead to use a system boiler, (pressurized), the pump and expansion vessel (now both in the boiler) there would be ~6M plus the inverted loop under the floor before the valves and manifolds. Is this a more sensible option? I want to avoid too many pipes under the floor, so I’d sooner do the S plan+ distribution in the old boiler location where there is also more space.
Fresh over from Electricians forum..
I built an extension. My old boiler (1970’s, half gravity, in-wall vertical sectional concrete flue) - has all gone.
75% re-do of the rads and plumbing underway.
New boiler location will be on the outside wall of extension which is now ~6M from the original boiler. HW tank and feed from loft tanks are vertically above the original boiler location.
My best bet I believe is to stick with an open vent boiler. The vent, inlet, pump, valves (S plan +) and distribution manifolds will be in the location of the old boiler. The expansion pipe and feed can run vertically up from this location.

The new boiler flow and return (22mm) will both need to take an inverted loop then a "uninverted" loop from the new build outside wall, beneath the new floor then above a ceiling to come out at the proposed location of the vent/inlet/pump. Horizontally this is about 6M, pipe length probably 9M. Should I expect any problems with this distance? I am assuming it would be essential to add some T pieces and air valves near the boiler for example, and the high points, also drain cocks, but this leads to two little questions:
- Air exit valves near the boiler?: I want to come out the bottom of the boiler to keep it tidy, so how do I arrange this re air vents? (Also any problems re excess heat and valve seats so close to the boiler?). Do I use automatic valves?
- Is it OK to have an inverted loop and ~ 6-7M of 22mm pipe between boiler and Open vent/Inlet/Pump? Might I expect any other problems?
If I decided instead to use a system boiler, (pressurized), the pump and expansion vessel (now both in the boiler) there would be ~6M plus the inverted loop under the floor before the valves and manifolds. Is this a more sensible option? I want to avoid too many pipes under the floor, so I’d sooner do the S plan+ distribution in the old boiler location where there is also more space.