What pressure should your boiler be?

What causes low boiler pressure?

There are a few things that can cause low boiler pressure, including:

• Leaks - your boiler can lose pressure if there is a leak in the pipes or valves. Check your water bill to see if you are using more water than expected, which could indicate a leak
• Bleeding your radiators - when you bleed your radiators, air is released from the central heating system, which lowers the boiler pressure. Always check the boiler pressure after bleeding your radiators to make sure it’s not too low.

It’s important not to keep using a boiler with low pressure as it can damage the boiler. Low pressure also means your boiler will be less efficient, leading to higher energy bills.

How to fix low boiler pressure problems

Follow these steps to repressurise the boiler:

1. Switch off the boiler: make sure the boiler and central heating is switched off. Wait for it to cool down if necessary.
2. Find the filling loop: This is usually a flexible silver pipe that connects the mains water to the heating circuit.
3. Open the filling loop valves: Open the valves at both ends of the loop so that water can be transferred from your mains supply into the heating system – you should hear the water moving through the pipe.
4. Wait: Keep an eye on the boiler gauge, which should increase as water moves into the heating system.
5. Close the valves: Once the boiler gauge reaches 1-1.5 bar, close the valve.

Before you do anything, always check the boiler instruction manual to make sure you’re following the correct steps. If you’re not confident following the procedure, look for a recommended professional.

How to repressurise a Worcester Bosch boiler

Fixing low Worcester Bosch boiler pressure problems can be slightly different if the boiler uses an internal filling key rather than a filling loop. Here’s what you need to do:

1. Switch off the boiler
2. Remove the hatch underneath your boiler to access the internal filling key
3. Locate the filling link by looking up inside the boiler – it’s a small hole to the right of the white square where the internal filling key needs to be inserted
4. Insert the filling key into the filling link firmly – push it in until the arrow on the key’s side almost meets the black plastic. Turn the key anti-clockwise so the arrow faces towards you
5. Now gently turn the white square clockwise – you should hear mains water entering the system. Wait until the pressure gauge increases to between 1.0 and 1.5
6. Turn the square in the opposite direction (anti-clockwise) to shut off the water
7. Remove the filling key from the filling link – some water may drip down, so have an old cloth or towel ready beneath
8. Switch the boiler back on – if necessary, also press the reset button.

As always, check the boiler’s instruction manual for step-by-step instructions before you begin.

What causes high boiler pressure?

Your boiler pressure could be too high if:

• You’ve accidentally overfilled the system by putting too much water in when trying to correct low boiler pressure
• You’ve left the filling valves open by accident – this means water will still be flowing in, increasing the pressure as a result.

Don’t keep using a boiler with high pressure, as although there are safety mechanisms to avoid system failure – including a valve that can let water escape as well as a safety shutdown measure – it could lead to leaks or bursts.

How to fix high boiler pressure problems

If your boiler pressure is too high, try the following steps:

1. Switch off the boiler and let it cool down completely.
2. Check that the filling valves are completely closed.
3. Bleed one or more radiators to release excess water and pressure (you’ll need something to catch the water as it comes out of the radiator bleed valve).
4. Continue bleeding until the pressure gauge drops to around 1.2 bar in the green zone.

As with low pressure problems, always check the boiler instruction manual to make sure you’re following the correct steps. If you’re not confident following the procedure, look for a recommended professional.

When should I call a professional to investigate boiler pressure issues?

If you’ve tried fixing the boiler pressure yourself but it hasn’t worked, it may be time to call a professional. Make sure you use a qualified and registered Gas Safe engineer as only they are legally permitted to work on boilers in the UK.

Never take risks with boiler issues that seem unsafe or complex. If in doubt, it’s better to call in a boiler expert rather than damage your boiler further or risk being without heating or hot water.

Likewise, if you suspect a leak or have ongoing water pressure problems, it’s a good idea to be proactive and get your boiler checked. Summer is the best time to find a boiler engineer with availability at the cheapest rate.

How to prevent boiler pressure problems

There are a few things you can do to maintain good boiler pressure and to avoid boiler problems:

• Regularly check your boiler pressure
• Get your boiler regularly maintained so any problems with pressure are detected before they become serious
• Book an annual boiler service
• Bleed your radiators periodically so that the pressure isn’t too high
• Be vigilant about leaks.