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Water coming out of overflow pipe on start up.

Postby creekybones » Fri Nov 21, 2008 7:14 pm

Hi All,
When my central heating starts up I get some water coming out of the header overflow. After 5-10 Mins it stops.

I have bled the Radiators but still happens

Any Advice?

Thanks in advance

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Simply Build It

Postby plumbbob » Sat Nov 22, 2008 4:24 pm

Oh, ?I do wish DIY doctor would publish an article in the projects section, as this type of fault appears here again and again and it is tiresome to keep repeating the same reply.

Basically, it is caused by a poorly designed system where the feed and expansion pipes are connected to the system too far apart causing a pressure difference between each resulting in either water being forced up the expansion pipe and over into the header tank or conversely, water being drawn down and air being sucked in.
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Postby Steve the gas » Sun Nov 23, 2008 6:12 am


Lower the level of water in the tank by adjusting the ball valve.

Steve the gas
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Postby creekybones » Sun Nov 23, 2008 7:34 pm

Thanks guys, The Feed & expansion pipes are right next to each other & tee into each other just before the pump. So I take it they would be ok, I will try lowering the level as its an inch below the overflow pipe.

Thanks for both replies
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