Fit a New Pump.All the domestic central heating pumps fitted now come in a standard type and size, but you may have a slightly older pump that might be different, perhaps longer than its replacement which, means you may need to fit extension pieces to allow for this.Prior to purchasing your replacement pump you should take all the details from the original; and write them down so that you can tell your supplier all the relevant information so you get the correct pump. Domestic pumps are available with different strengths. A London Boiler Installations tradesperson can supply and fit new appliances.Isolate the electrical supply to the central heating system and pull out the plug. Sketch the electrical wiring on the old pump. A good idea is to label each wire. Then disconnect the wires with a screwdriver.Close off the isolating valves either side of the pump using the valve handles or an adjustable spanner. If there is no isolating valves drain the system. Place a bowl and towels under the pump ready to catch any water as you remove it. Undo the union nuts holding the pump. Turn them anticlockwise.Now remove the old pump. A qualified tradesman employed by London Boiler Installation will remove an old pump. Put the new pump in position using the new sealing washers in the unions. Open the isolating valves (or refill the system) and check that the unions are watertight, then, re-connect the wiring.Switch on the electrical supply and try the new pump by turning on the central heating system at the programmer or time switch. You may also need to turn up the room thermostat. When the central heating system is running, check that the open safety vent pipe over the feed and expansion cistern does not discharge water when the pump starts or stops.If you have to add too much freshwater to the cistern, bleed any air out of the system in order to guard against future corrosion and to protect the new pump.“