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connecting a combi boiler to low mains pressure?

Postby md4t » Thu Nov 04, 2010 8:07 pm

Is it possible to connect a combi oil boiler to low pressure mains?
I want to install this type of boiler to a new house I am building. Not sure of the exact pressure available but the flow rate to a stand pipe on site which was the main feed to a previous building is 18 litres/min at ground level.
However, the farmhouse next door(150m away) is achieving 27 litres/min from an outside tap.
I am considering one of two options:
1, To renew the water pipe the full 150m back to the meter with a larger bore to try and achieve a better flow rate.

2, Installing a pressure booster pump. Is this even possible to do without having a large cold water storage tank in the loft to draw from?

Please advise
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Simply Build It

Postby plumbbob » Mon Nov 08, 2010 8:30 am

Really whether a combi will work is only the tip of an iceberg. The water pressure needs to be greater than 1 bar (pref 1.5 bar) to enable the system to be pressurised sufficiently to fire up at all. If this can be achieved, then the boiler will work.

Deciding if the flow rate is sufficient to enable you to fill a bath quickly enough or even have a decent shower is a different matter.

Oh, and you are right about the pump as they can only pump not suck water up a pipe.

What is the old main? Is it corroded and likely to fail in the near future? Personally, I would seriously consider replacing the existing main for a new 25 or even 32mm mdpe. It's only a few quid for the pipe, and if you have builders or a digger on site.......
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