Draining a Central Heating System

Heating system mounted to a ceiling

Draining central heating system water is an important part of necessary system maintenance. For these heating systems to operate efficiently, it is not always advisable to wait until a system problem has developed before performing maintenance. Periodic maintenance will often make it possible to find potential problems before they happen. In some cases it will prevent problems. It is for this reason that maintenance of these systems should include draining of the system water. This can also be required during repairs. For proper and effective system draining procedures, check the information below.

System Repairs That May Require System Draining

Where radiator leaks are found, where a central heating system is blocked by sludge or debris, or where valves and other system components become worn and need to be repaired or replaced, system draining is often required. When these repairs are made you should always include draining of water from the heating system before proceeding with your repair.

Preparing for System Draining

When preparing your system for draining, you will need to ensure that water is prevented from entering the cistern during the draining procedure. In addition, you will need to shut off the system's electrical power and natural gas. Typically, you will be able to do this by finding switches or valves that control the flow of gas, water, or electrical power. If you are unable to stop the flow of water by shutting off a water valve, you can often arrange a ball valve in a position to stop this water flow by tying a ball valve to a long piece of wood that has been placed across the cistern top.

The Draining Procedure

Typically, you will drain your heating system's water by attaching a hose to the boiler's drain cock and placing the far end of the hose out of doors where you can safely drain the water without creating flooding or other drainage problems. You will usually find the drain clock at the underside of the boiler. When you have located the drain valve and have securely attached the drain hose to the drain cock, the drain valve should open if you turn it counter-clockwise.

Speeding Up the Drain Process

System water will drain faster if you reduce pressure in the boiler by opening all system valves and air vents. In opening these vents and valves you should begin at the upper floors. Lower water levels in the boiler will normally result in slower draining of the water. You can speed up this flow by opening in the lower floors all the radiator valves and air vents. When the flow of water has stopped, it may be because of air pockets in the system that block the flow of water. To be sure all water has drained, you should check the system for these air pockets by opening the ball cock. This will permit water to then begin flowing. Water from all parts of the building should then drain, leaving the system completely drained.