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Sealed central heating systems: draining down and refilling

To carry out maintenance work on a sealed central heating system, you’ll need to drain down the system. Whether you are carrying out repairs or making a modification such as fitting a new radiator, a sealed system must first be drained down, then refilled after the work has been completed.

Sealed central heating systems

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Understanding your heating system is important, and ensuring you have a cost-effective and efficient system is vital. Saving energy and cutting costs may require replacing your boiler with a more efficient model.

Draining down the system

Turn off and disconnect the boiler from the power supply to reduce water pressure and avoid scalding yourself.

Locate the drain point; this is usually found on the pipework by the lowest radiator at the lowest point in the house. Attach a hose and secure with a jubilee clip. Run the hose outside to a drain-off point, ensuring it runs downhill so the water flows.

Open all radiator valves so the pipework drains. Open the drain valve using a spanner. Check that the water is flowing down the hose to the outside drain. You can speed up the process by opening the air vents at the top of the radiators.

The heating system is empty once the water stops flowing. You’re now able to carry out any maintenance work required. If you need a plumber, check out http://www.ciphe.org.uk/ or if you require a boiler installation in Woking, find an experienced and professional company such as boiler installers in Woking http://www.rjplumbingandheating.co.uk/.

Refilling the system

Close all radiator air bleed valves, closing the drain valve last. Undo the jubilee clip and release the hose, lifting it high to drain any residual water out.

Open the filling loop so water flows back into the system.

Open the bleed valves on all radiators to release any air, starting downstairs first. Finish upstairs to reduce the risk of trapping air in the system. Once all air is released, top up the system by opening the filling loop.

Check for any leaks, then turn the boiler back on and run the heating as normal. Bleed radiators several times as air is forced out by the heating process. Check the pressure gauge and top up as required. Finally, check for leaks; a connection may be watertight when cold but may expand and leak when warm.

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