The non-return valve, also called a stop check valve, is usually positioned on a pipe between the boiler and the feed pump. Through this valve, hot water vapor from the boiler can be stopped or started. It consists of a disc and a stem, and it can be closed by turning down the stem and shutting off the flow. In normal conditions, the valve stops return flow from the boiler from entering the feed line when the pump is turned off. When the pump is turned on, the valve ensures normal water flow to the boiler.
Without gadgets like valves a boiler cannot run efficiently. A boiler needs various external devices that monitor its performance and watch out for erratic activity that may cause problems. Removing or replacing a broken non-return valve is maintenance work that is necessary if the boiler is to function properly.
Step 1 – Turn the power off
Turn off the power to the boiler, in order to prevent burning up its heating elements, by shutting the power off at the service panel.
Step 2 – Let the boiler cool down
Let the boiler cool down for at least 3 hours after turning the power off. Working on a hot boiler can cause severe burns on your hands. Even if you are in a hurry, do not use cold water to cool the boiler because this will cause its collapse. The cold water that gets into the hot boiler will cause the water to suddenly contract, leaving a partial vacuum. Without the resistance within, the external pressure of the atmosphere from the exterior will crush in the sides.
Step 3 - Drain the boiler
First shut off the water supply. In order to do that, you need to look for the shut off which is usually somewhere near the fill valve of the boiler, or anyway on the same pipe with the fill valve. Find the boiler drain, positioned somewhere near the bottom of the boiler. Screw the end of a garden hose to the drain and put the other end near the floor drain, in a sink or take it outside. Lift the relief valve, to vent the tank, and then open the boiler drain valve slowly, so the water will flow in a steady stream. After the boiler has finished draining, close the drain valve and unscrew the garden hose.
Step 4 – Remove the valve
Take off the nut from the inlet on the one side of the stop-check valve, and put it away or store it if you think you might need it later. Use the wrench to hold the other side. Take care not to twist the pipe. The stop-check valve is connected from both sides to the water pipe, so you need to remove the nut on the other end too, by holding the other side of the valve. Hold the pipe to which the valve is connected, and carefully remove one end of the valve and then the other. It should be a very easy thing to do.