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How to Top Up Boiler with Water – Turning Pressure Up on a Combi Boiler

Here’s how to top up a boiler with water. Turning the pressure up on a Combi Boiler is easy and here is how to do it and get your heating back up and working in a few minutes.

So, if your boiler has cut out and you see the pressure gauge is below the green or black marked range and into the red area, try to stop shivering for just a minute, read on and get this done!

Make sure there is water in the system

Before you start take a reality check! Is it possible the heating has been drained and has been decommissioned for any reason, maybe while you were away from home? Just stand back a moment and think before starting this!

Don’t worry if you put in too much water pressure; the boiler should have an in-built safety system that will dump the surplus water if you put in too much.

Your combi boiler’s pressure should be between 1 and 1.5 bar. If your pressure is less than 1 bar, you may have lost water from the system due to very slow a leak. Boiler systems are never perfect and after many months will lose pressure in this way, it’s normal. But before starting do just examine the area around the boiler and the home for any signs of leaks.

Topping up a boiler with cold water from the mains is a typical part of maintaining a boiler’s life cycle.

You may have noticed that your heating is less efficient or that the pressure indicator on your boiler has turned red.

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Check your Pressure Gauge

To check the pressure in your boiler, first, locate the pressure gauge. Typically, you’ll find it on the appliance’s front panel.

Check the pressure gauge on the control panel for a reading. You must increase pressure if the needle is in the red (below 1 bar).

Determine the location of the boiler pressure gauge and inspect it. If it’s over 2 bars, don’t put any additional pressure.

If the gauge is over 2 bars, bleed the radiator until it returns to the typical range of 1 – 1.5 bars.

Consider hiring a plumber if the boiler does not reset and restart when you turn the dial to make it do so after you’ve done all of the above and waited a few minutes. Something more significant than a requirement for re-pressurising is most likely amiss.

Steps on how to Re-pressurise Your Boiler

Before you call a professional, read on to learn how to re-pressurize your boiler on your own.

To operate at peak efficiency, your combi boiler system requires consistent water pressure.

The flow of cold water taken from the main water supply through the filling loop maintains a consistent level of water pressure in most modern combi boilers.

Re-pressurising your boiler using a filling key

Allowing extra water to enter the system from the water main supply through the filling key, which activates the filling loop. A “filling loop” from the water main is included for all combi boilers This is known as re-pressurising your boiler.

To begin, make sure the valves on the filling loop are properly closed, as they may have loosened or been mistakenly left open after re-pressurising your boiler previously. Then, instead of using your key, proceed to the following section for valve operation.

Re-pressurising your boiler using a filling loop

If your boiler has a filling loop, follow these easy procedures to repressurize it.

To begin, turn off your boiler if it is currently in use and allow it to cool.

Once the boiler has cooled and the filling loop has been located, you may begin to increase pressure to the boiler.

Slowly turn one of the valves while watching the pressure gauge to see if you can hear any running water or see the pressure gauge rise.

If not, carefully turn the second valve once the first is fully open, and the pressure should begin to build.

When the pressure gauge is well above the low-pressure area indicated on the dial, close the water valve or key.

That is it! You’re done, and you may turn the boiler back on using the boiler’s standard reset/start settings – typically, a dial switch on the front of the boiler.

How to Top Up Boiler with Water – Closing Thoughts

Repressurizing a boiler is a reasonably straightforward task that may be completed by a homeowner. You should be able to do it without the assistance of a heating engineer. To assist you, we’ve put a video to this page.

Before attempting to boost your boiler’s water pressure, please watch the video all the way through.

The pressure should be between 1 and 1.5 bar when the heating system is cold.

If the pressure is too low, say less than 0.5 bar, water has leaked out of your system and has to be replaced. When the pressure in the system is too high, it might mean there is too much water in the system.

If you choose not to handle it yourself or are unable to do so, the Customer Support department of your Gas Safe licenced engineer or boiler manufacturer/installer would gladly assist you for a fee.

However, there are two major techniques for topping up your boiler: an external filling loop or an internal filling loop (keyed or keyless) – all of which are discussed here or in the video and step-by-step tutorial above.

If this does not resolve the pressure issue or you continue to have to top up your boiler on a regular basis, it is critical to identify the source of the problem in order to safeguard your boiler from further harm.

If you’re unsure how to repressurize your boiler, get expert help.

Pressure difficulties in boilers quite often mean their replacement is required sooner rather than later.

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