Low Gas Pressure To Your Boiler? Here’s What To Do

While modern gas boilers are truly useful machines, like all things in life, they’re prone to failure. That means that you’ll need to regularly maintain them and give them a bit of love here and there – and that’s normal. If you notice that you’ve got low gas pressure to your boiler, there are a few things to keep an eye out for.

The most common causes for low gas pressure to a boiler are a leak or a reduced system pressure due to bleeding a radiator.

Now without further ado, here’s how to fix the issue that brought you here in the first place!

Troubleshooting Low Gas Pressure to the Boiler

At least in the UK, most homes use a gas combi heater to heat water. These will generally have a pressure gauge located on the side near the control panel. It’ll look similar to the photo below, and you’re looking to have it in the green zone. This should be between 1-1.5 bar (14-21 PSI for Americans) for ideal gas pressure. If it’s in the red zone, you’re getting too much pressure, though it’s unlikely that’s the case if you’re here due to low pressure.

If the needle has fallen below the green line (1 bar) you’ve got a problem, and assuming your radiators aren’t heating up as usual, this is a strong sign that there’s a problem with your boiler pressure.

Is Low Pressure a Problem?

Long story short – no. While low gas pressure to the boiler is inconvenient and will impact your heating bill, it isn’t outright dangerous. On the other hand, a pressure that’s too high is a problem that should be addressed immediately by a licensed professional.

One way or another, there’s no sense in ignoring the issue, as low pressure will make your home less effective in staying warm and will cost you an arm and a leg. And nobody wants that, do they?

Low Gas Pressure: Causes & Fixes

Like we said in the introduction, the two major causes of low gas pressure to the boiler are a water leak or a bled radiator. While the former can be a major issue, the latter is actually rather easy to fix yourself.

Here’s a bit more information.

Water Leaks

First things first – take a look at our related article. While its focus is slightly different, the process is very similar. For those who don’t want to read another article, here’s a basic guide:

  1. Begin by walking the lenght of your home, looking at all of the pipes you can find. Follow their path through your home, keeping an eye out for any sign of moisture.
    1. You may notice mould, dark patches or stains, or swelling. If you have copper pipes, you’ll notice them turning green if you have a leak anywhere.
    2. Joints are the most common point for leaks to occur, so pay extra attention to them.
  2. Look for condensation – this is not the same as a leak. If you’re in a cold, wet environment (such as the UK) pipes that are exposed to cold, wet areas will develop condensation – this is okay. That’s not to say you shouldn’t try to address this too, but it’s not your most immediate concern.
  3. End by checking your boiler. If there is any sign of moisture near it (or inside, as detailed in the article above) then it’s time to call a professional for help.

Bled Radiator

If you’ve been reading our articles for a while, you’ll know that we taught how to fix cold radiators by bleeding them. While this is a common (and good) practice, it can cause a drop in boiler pressure. For the uninformed, bleeding a radiator removes air that’s trapped in the pipes, allowing hot water to take its proper place in the radiator.

How To Fix Low Gas Pressure to Boiler

Here’s where the fun begins. To fix low gas pressure to your boiler, you need to repressurise it. While this can generally be done at home without a Gas Safe engineer, it’s best to double-check. Not all boilers can be serviced like this – so do your homework before attempting. Now, here’s the fix.

The Process:

  1. Find your filling loop and pressure gauge. The loop handles are generally at a 90 degree angle to the pipe. (If your pipe is vertical, the loop will be horizontal, and vice versa.)
  2. Get a good view of your gauge while getting to the filling loop. You’re going to be cross-referencing what you’re doing with the gauge to get it to the perfect pressure. While you can just try to get it in the green, it’s best to check what your boiler’s ideal pressure is and get it as close as possible.
    1. If you can’t see the gauge while accessing your filling loop, get a friend to watch the gauge for you.
  3. Turn off the boiler
  4. Turn both filling loop handles so that they align with the pipes. This should cause a flowing water sound to appear – this is good.
  5. Keep slowly turning the handles until you’re at your ideal pressure, and then slowly fully close them once you’re at the desired pressure.
  6. Turn the boiler back on and test. If it’s not where you want it, repeat steps 3-5 until you’re at the desired pressure, or call a professional for help.
    1. If you have the pressure at the ideal level and then it drops again, it’s time to call for help. There could be another issue at play, and a professiona’s eyes will spot it much more quickly than you will.

Final Thoughts

Boilers are complicated and important parts of our home. If you find that you’ve suddenly got low gas pressure to your boiler, there are a few things to keep an eye out for. If you’ve recently bled a radiator, you’ll likely need to repressurize your boiler as detailed above. This is the ideal problem, as it can be dealt with rather easily at home without the help of a professional.

If, however, you haven’t recently bled a radiator in your home, it’s possible that you have a leak somewhere along the line. This is a much more serious issue that can’t be addressed without a plumber, and you really don’t want to ignore this. If you spot signs of water damage in your home, such as corroded pipes, water spots, or puddles (obviously), you need to get it addressed ASAP. Don’t, however, mistake condensation for a leak. While condensation is something to address, it’s not as vital as a leak.

And as always, please don’t hesitate to call a professional. If you’ve gone through the effort to troubleshoot, you’ve already done more than many homeowners do and your plumber will thank you. You just made their life easier, and they’re about to make yours easier.

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About the Author Harry Thompson

Involved in home renovations throughout his life, Harry is an expert in everything to do with home and garden DIY. In his spare time, he enjoys cooking and tending to his garden.