How to Repressurise A Boiler Without the Filling Loop

If you own a boiler, low pressure is one of the problems you might have to deal with occasionally. Luckily, you don’t need an expert to help you repressurise the boiler. All you need is your user manual and some will to find the filling loop on your boiler.

If the boiler has a filling loop, things get incredibly easy for you. If not, you have to find a way to add water into the boiler to increase the pressure. There are several ways you can go about this, depending on the type of boiler and repressurisation mechanism in place.

Repressurising using a filling key

Some boilers come with a filling key or filling taps instead of a filling loop. The mechanism of the boiler depends on the age and design of the boiler. But, the operation of the two features is largely the same.

Turn off the power to the heating system

You don’t want to run any risks while filling the boiler. Turn off the power and wait for a few hours until the system completely cools down. If you don’t turn off the system and give it ample time to cool, you could easily hurt yourself.

Find the concealed tray

There’s a concealed tray usually under the boiler. In newer models, the tray might be made out of plastic while in older boilers it could be made out of metal. Gently pull out the tray. You will find a filling key attached to the tray.

Remove the filling key

Remove the filling key from the tray by releasing it from the holding mechanism. Once you have the key in your hands, observe its shape and try to locate a manifold keyhole with a shape that matches that of the key. In most cases, the keyhole is located next to the manifold nut. Gently slide the key into the hold and make sure it fits snugly into the manifold.

Use the key to unlock

You will notice the keyhole has a locked padlock symbol and an unlock symbol. Turn the key towards the unlocked symbol position. Ideally, you will have to turn the key through a 45-degree angle. Once in this position, the key should feel completely secure in the manifold.

Why not also read: How Long Does a Boiler Last?

Rotate the manifold nut

With the key in the unlocked position, turn the nut (usually located next to the manifold keyhole) slowly and gently to counter-clockwise. One the nut moves about 180 degrees you should hear the water start moving into the boiler system and the pressure will begin rise.

In some systems, instead of the key and nut system, they have two taps which might be located at different locations in the house. One near the boiler and the other might be under the kitchen sinks.

Other systems like a variety of Potterton boilers only have one tap which is usually not near the boiler so you have to try and locate it around the house. Regardless of the system in place, rest assured they all achieve the same result. Be cautious not to exceed the recommended boiler pressure which is usually 1.5bars. If you exceed the pressure, you can turn the release knob on the nearest radiator to release the extra pressure.

Once the gauge hits the right pressure, turn the nut back to its original position followed by the key. Return the key to the holding spot on the tray and replace the tray back under the boiler. Your low-pressure issue should now be solved.

If the problem is recurring, consider having a Gas Safe registered engineer check the system for leaks which can cause the pressure to drop. If there is a leak, it needs to be repaired as fast as possible to prevent further damage to the system.

As the leading Boiler Installation Company in Nottingham, we can help you with any queries you might have about repressurising your boiler, or any other questions you may have.

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