Zone control valves are another name for the valves that monitor and help control central heating systems, having a direction of flow marked on the body which is very important within a system carrying water. The direction of flow should always be marked before disconnection and removing of any valve.Two types valves feature in nearly all central heating systems. They are electrically driven.The first valve is known as a two port valve which operates in an ‘on’ and ‘off’ action. The second is called a three port valve or ‘Diverter Valve’ that diverts the water flow through the cylinder for the hot water when it is required to do it. Willesden Plumbers are familiar with the supply and fitting of these valves. Valves are a fairly basic component of the system but are very long lasting, and capable of decades of hard constant use by the central heating system. Like a lot of hard working things, the valves can start to show their age, and start to fail with usually the electrical components wearing out first, and secondly the seals which cause the leaks. These components are not really expensive to purchase but it is a good idea before purchasing a replacement valve to visually check and test the old one first just to confirm that the problem is not in the wiring or control timer, saving money. A Willesden Plumber is an experienced professional.If there is an emergency situation it is sometimes possible to disconnect the wiring for the valve, this will remove the control but still allow the operation of the system to continue, however the cable should be made safe by disconnection at the controller and manually opening the valve with a screwdriver or a small spanner. This procedure will result in there being no zone control.