DIY Doctor

Draining central heating

Postby CPShines » Fri Aug 01, 2008 8:43 pm


I want to drain down my sealed combi system so I can change some of the pipework and connect a new radiator. The drain valve is on the bathroom radiator. We're in a first floor flat so all the pipework is under our floorboards.

What I'm unsure about is the fact that the drain valve is obviously above the underfloor pipework, so how can I empty the pipework?? Should there be another drain valve at the lowest point of the pipes under the floorboards somewhere in the flat?

Ta in advance :)
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Simply Build It

Postby htg engineer » Sat Aug 02, 2008 3:16 pm

Ideally yes, but there probably wont be.

Connect hose to the drain valve, open all radiator vents, this will drain the radiators, but the pipework will remian full of water. You can work on the pipework above the floor, you will get abit of water coming out - but not much. If you're wanting to work below the floor, place a fish under the pipe and cut or crack open a joint.

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