How to Drain and Refil a Central Heating System
Without central heating system, you might as well be thrown back to the middle ages. The only method of heating back in those days was by lighting up a fireplace. To feed a fireplace you would have to chop wood and surely that was one job not worth looking forward to.
The innovations and inventions brought about by "necessity" and technology presented the modern man with choices as to how to conveniently heat up his home. The central heating system is one of the conveniences of modern man that is vital to his existence. Without heat, there could be no life.
A boiler is the heart and soul of a central heating system. It is that which heats up water and supplies the all the faucets in a household. There are three basic boiler types and they are: conventional, combination and condensing. A conventional boiler is the open-vented type which has two tanks up on the loft for the cold and hot water. The combination boiler has no water storage tank as water is heated up instantaneously. The third type is the condensing boiler which could either work on the principle of either a conventional boiler or a combination boiler. The big difference is that this type is more energy and cost efficient.
Maintenance is all part of the package when talking about central heating system. It is important to periodically check on the central heating system to avoid minor or major repairs. Draining the central heating system is maintenance work. However, note that not all types of boilers can be drained. The open-vented is the most common central heating system installed in most UK homes today. This type of central heating system is the only one that can be effectively drained for cleaning the radiators, flushing the system or repairing leaks. If your house system is either combination or sealed system then you need a specialist to do the draining.
Draining the Central Heating System
Draining the central heating system could be called for if there is a leak in the radiators, solid particles or sludge that can block the system, fix worn out valves and more. Draining and refilling the system is a simple-enough procedure.
Turn off the power of the heating system. Make doubly sure that the gas or electric power is off. Find all on and off switches on the boiler and turn them all off. Next turn off the water supply from the cistern. If you can't find the valve or if it's too stiff to turn, place a length of wood across the top of the cistern and tie a ball valve to stop the flow of water. Make sure that no water enters the tank when you are draining the system.
Make sure you have a jubilee clip when you attempt to locate the drain cock and attach a hose to it. The drain cock is usually found at the bottom of the boiler. When you have attached the hose, place the other end outside to drain. However, remember to run the hose outside where it would not cause trouble or accidents. Make sure you have located all the air vents running along the central heating system. Check all locations including the loft especially if it's being used as a living area.
Turn the drain valve counter-clockwise to drain the water. Speed up the draining process by opening the air vents or the bleed valves on all the radiators starting from the top level or floor. When the water level is low, open the remaining air vents or valves located at lower levels or floors. When no more water comes out, check for air pockets that could be preventing the complete draining process. You can check by loosening the ballcock to allow water to fill in. The water should automatically drain from the other end of the house. The central heating system is now completely drained.
Refilling the Central Heating System
You can immediately refill the central heating system. Start by closing all the radiator valves at the lower level floors. The turn on the water supply going to the cistern or untie the ball valve to let water flow in. To let water flow smoothly and steadily, open up one of the radiator air vents. Repeat the process of opening up air vents on the lower floor. As the central heating system fills up, repeat the same process of opening up radiator air vents in the upper levels or floors.
If the ballvalve in the cistern has enough water to float in, check that the water level is in low enough to allow room for water to expand when heated. If the water level is too high, turn off the water supply to the cistern and release some water by opening the drain valve. The arm of the ballvalve should be adjusted at the right position so the valve should close when the right water level is reached.
Cover the cistern and check that all valves are tightly shut. Turn on the boiler according to the manufacturer's instructions. As the water heats up, air will have to be vented so you have to "bleed" the radiators for a day or two. Don't be alarmed if you hear some knocking sound as the system heats up. Check for leaks in the system.
For other central heating systems like the sealed heating systems, draining and refilling is not as straightforward as this. If this is the type of system that you have, it is best to hire a qualified plumber for the job.
Be sure to periodically drain and refill your central heating system as a maintenance procedure. Proper care would give you a highly efficient system, performance-wise and energy-wise.
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"You can immediately refill the central heating system. Start by closing all the radiator valves at the lower level floors. The turn on the water supply going to the cistern or untie the ball valve to let water flow in. To let water flow smoothly and steadily, open up one of the radiator air vents. Repeat the process of opening up air vents on the lower floor. How does this work? if the lower rad valves are closed when refilling as stated how will water enter the rad to purge air via the bleed valves?"