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Why Is My Boiler Losing Pressure?

Why Is My Boiler Losing Pressure?

If your boiler pressure keeps dropping, it’s important to identify the cause sooner rather than later. Constant water pressure is required for your boiler to function properly and provide you with hot water. So, why does boiler pressure drop?

In this blog, we answer that very question – alongside giving plenty of sound advice around checking your pressure, preventing pressure drops and locating potential leaks.

What is boiler pressure?

Unlike traditional tank systems, the more common combi boiler of today uses an expansion vessel to supply your central heating system. As water volume fluctuates, the expansion vessel absorbs the high pressure when your boiler heats up. Your pressure gauge – often located front and centre on your appliance – allows you to view operating levels.

What causes the pressure to drop in a boiler?

Bleeding a radiator is one common cause of a pressure drop. Another is a leak, either within the boiler or elsewhere in your heating system. This could be due to loosening parts or corrosion causing water to escape and the pressure to reduce.

If it isn’t for either of these reasons, you may have an issue with the boiler itself. This could be down to a faulty pressure relief valve or other malfunctioning boiler parts, at which point you should call an engineer.

How do I check if my boiler pressure is low?

When checking the pressure on your boiler, know that a general range of 1 and 2 is ideal and could be described as the correct pressure. While there is room for a little on either side of these levels, it shouldn’t drop below 0.5. If the gauge on your boiler reads below this, your boiler pressure is too low.

However, we always recommend following the indicators located on your specific boiler or in your boiler’s manual.

How can I avoid my boiler pressure dropping?

If your boiler keeps losing pressure, you can usually repressurise the system. First, check your manual to see if your model allows you to fix low boiler pressure in this way. If you get the green light, follow these steps:

  1. Switch off your boiler, allow it to cool, and find your filling loop.
  2. Turn to open the filling loop handles, at which point you should hear water flowing.
  3. Watch the pressure gauge and allow it to increase to the recommended level stated on the gauge and/or your manual (usually around 1.5).
  4. Close the filling loop handles completely and turn your boiler back on.

If pressure isn’t maintained after these steps, it’s time to call the professionals. You may find that you have a leak or you need boiler repairs.

How Rainbow International can help

If you suspect a leak in your home, Rainbow International can help. Our trace, access and water leak detection services can pinpoint the exact source and repair the issue before it escalates.

With a wealth of expertise and specialist equipment, we can help identify a leak with thermal imaging, acoustic testing, tracer gas and pipe tracing. Once located, we can even get to work on restoration – whether that involves fixing the leak or repairing damage from damp patches.

Visit our leak detection page to find out more.

Frequently Asked Questions

How do I find a leak in my boiler?

Leaks commonly occur around connections on radiators. Also look for discoloured paint, flaking, or water stains around the home. To accurately find a leaking pipe, you may need the help of a professional.

Can boiler pressure drop without a leak?

Yes. It can also drop due to bleeding radiators or a faulty boiler.

Is it dangerous when my boiler pressure drops?

No, low pressure isn’t immediately dangerous. However, you may find that you’re only able to access cold water.

How often should a boiler lose pressure?

While there’s no right or wrong answer here, if your boiler is losing pressure daily or weekly, there may be a deeper issue to resolve.

How often should boiler pressure be topped up?

It’s common to need to repressurise your boiler up to once or twice a year. See your pressure gauge for guidance.

Published: 15 Dec 2021

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