How to Re-pressurise a Boiler

If there is no hot water or heating left in your home, then there is a chance you are experiencing low boiler pressure. Although you might find this intimidating, there is no need to worry because this guide will provide you with a step-by-step process to repressurise your boiler.

Before you attempt to repressurise your boiler, you must first confirm that your boiler is in fact suffering from low water pressure. To do this, you can look at the water pressure gauge on the front of the boiler. Depending on the model, boilers will have different pressure gauges. If in doubt, you can find the relevant information in the user handbook to ensure you make the correct judgement.

If your boiler has a digital gauge, then the water pressure will be displayed with bars. If the reading is showing less than one bar, that indicates that your boiler currently has low pressure. With a boiler that has a hydraulic gauge, the reading will most likely be on a dial. On the dial, there will be red sections, whereby your boiler pressure will either be too low or high, depending on which side the needle is pointing. To stop any evolving issues with your hot water and heating, then you should take a water pressure reading regularly.

When you bleed your radiators, you are letting out air. This is the most common cause of a sudden drop in your boiler’s water pressure. The other reason for a drop in your boiler’s pressure is that there might be a leak in your heating system. A water leak will most likely be the explanation if your boiler pressure has decreased gradually. Signs of your boiler leaking should be easy to spot, although, if not the leak may be under your floorboards or inside the boiler. In this case, the best thing you can do is call a qualified engineer to assess the issue.

Before trying to repressurise your boiler, you should read the manufacturer’s manual, as every boiler works differently.

Most boiler models work with a filling loop. In any case of repressuring a boiler, you must first switch off your boiler. You then need to find the filling loop and make sure that both ends are attached and secure, with one end connected to the central heating system and the other to the mains water supply. Following on from this, open the two valves. You should now be able to hear the mains cold water entering the system. It is important you keep the valves open until the pressure reading on your boiler gets to 1.5 bars. When this happens, close the valves and switch the boiler back on. Ensure you also take the time to reset your boiler if necessary.

There are some boiler models that have a repressure key. In this scenario, once you have turned the boiler off, find the tray underneath the boiler to locate the key and slot. Then, insert the key, so it is facing the open padlock symbol. Turn the key to the right, until it is next to the closed padlock symbol. After that, turn the white knob to the left of the key. You should now start hearing the water flow into the boiler. When the pressure dial reaches 1.5, you can turn the white knob back off. Your boiler will now be at the right pressure, so you can turn the key back, take it out and put it in the tray underneath the boiler.