Boiler pressure too high? Let’s fix it fast 

What’s the right boiler pressure?

Your boiler’s pressure gauge should read: 

• 1 bar when the heating is off 

• 1.5 – 2 bars when the heating’s on (that’s the sweet spot) 

• 2.5+ bars - that’s too high 

Most boilers show the safe zone in green - easy! 

Safety first ⚠️ 

Don’t fancy fixing it yourself? Don't risk it and let a Gas Safe registered engineer do the job instead. To save you searching, our expert engineers are just a few taps away. 

Signs your boiler pressure is too high

If your boiler pressure is outside the green zone and creeping up towards 3 bars on the dial, then you might also notice: 

• Weird noises – gurgling, banging, or whistling? Your boiler’s stressed. A low humming noise when it’s firing up is all you should be able to hear. 

• Sudden shutdowns – if there’s a problem under the hood, some modern boilers shut off automatically to keep you safe. 

• Leaks – high pressure can force water out through the pressure relief valve or weak spots in the pipework. 

Why is my boiler pressure too high?

We’ll help you get to the bottom of it...

• Faulty filling loop: A filling loop lets you add water to your boiler system when the pressure gets too low (this can happen when you bleed your radiators). If this is damaged or the valve is open it can let water into the system, driving up the pressure.    

• Expansion vessel issues: This helps absorb pressure when the water heats up, so if it’s not working then pressure issues are bound to follow.    

• Dodgy pressure gauge: If everything else seems okay, but the pressure still looks high, it might be a problem with the gauge. 

How to lower boiler pressure

Bleeding your radiators is a quick and easy way to lower your boiler pressure, but you should keep an eye on it as this might only help in the short-term if there’s a bigger problem lurking.  

Method 1: Bleed your radiators

Bleeding your radiators gets rid of extra water in the system to reduce the pressure. Here’s how it’s done: 

Method 2: Use a drain-off or filter valve

Drain off valves are a handy part of your plumbing system that help you get rid of excess water, to reduce your boiler pressure. Here's how:  

Method 3: Call in the pros

If the pressure keeps climbing, the fixes don’t work, or you just don’t have the time or confidence to fix it yourself, fast forward to finished with Ding...   

A Gas Safe registered engineer can: 

• Replace faulty valves. 

• Recharge or swap the expansion vessel. 

• Diagnose deeper issues. 

• Replace a faulty expansion vessel. 

• Fix a stuck filling loop. 

• Repair a broken pressure gauge. 

Boiler pressure too low instead?

If your pressure is under 1 bar, you might need to top up the water using the filling loop. Or there could be a leak in your heating system if the pressure continually drops.  Try Ding today. Home repairs made simple. 

Written by:

Martin Garbutt

Head of Technical

Martin has more than 30 years' experience in the gas industry working in all sorts of roles; from gas regulators to the private sector.

At Ding, he makes sure the technical information we share in the field and online is up-to-date and accurate. That includes helping to write helpful articles like this one.

View Martin's profile