How to Repressurise Your Glow Worm Boiler: 8 Step Guide

Repressurising a Glow Worm boiler is a straightforward job you can often do yourself. Turn off the boiler, locate the filling loop underneath, open the valves slowly to let water in until the pressure gauge shows between 1 and 1.5 bar when cold, then close the valves tightly and restart the system.

How to Repressurise a Glow Worm Boiler in 8 Steps

Follow the steps below to repressurise your Glow-worm boiler safely.

Step 1. Get the Tools You Will Need to Repressurise Your Glow Worm Boiler

Gathering the right bits before you start makes the whole job quicker and safer. Most Glow Worm models only need basic items you probably already have around the house.

• A flathead screwdriver (handy if the valves are stiff or need a quarter turn)
• A cloth or old towel to catch any drips
• A torch if the area under your boiler is a bit dark
• Your boiler manual (useful for checking your exact model)

Safety first. Always turn off the boiler at the electrical isolator and let the system cool down for at least 30 minutes. Hot water in the pipes can cause nasty burns. Never force anything and if you smell gas at any point stop immediately and call the gas emergency number. If you feel unsure at any stage, do not take risks. Contact a Gas Safe registered engineer instead.

Step 2: Check Your Current Boiler Pressure

Knowing exactly where the pressure sits helps you add just the right amount of water without overfilling the system.

• Look at the pressure gauge on the front of your Glow Worm boiler or on the digital display.
• The needle or reading should normally sit between 1 and 1.5 bar when the heating is off and the system is cold.
• If it shows below 1 bar or you see a low pressure warning light or fault code, it is time to top it up.

Step 3: Turn Off Your Heating System

Switching everything off prevents the boiler from trying to run while you add water and reduces any risk of scalding.

• Turn the central heating and hot water off at the boiler controls.
• Switch the boiler off at the wall isolator if it has one.
• Wait at least 30 minutes so the pipes underneath cool down.

Step 4: Locate the Filling Loop on Your Glow Worm Boiler

Finding the filling loop is key because this is the part that connects your mains cold water to the heating system. Glow Worm combi boilers usually have either a flexible silver braided hose with two valves or a built-in filling link.

• Look underneath your boiler for a short flexible hose with a valve on each end.
• Some newer models like certain Energy or Easicom versions have a white or plastic pull-down knob instead.
• Check your user manual if you are not sure which type you have.

Step 5: Connect or Prepare the Filling Loop

Getting the loop ready ensures water can flow safely into the heating circuit without leaks.

• If the hose is detachable, connect it securely to both valves.
• Make sure all connections are tight but do not overtighten.

Step 6: Slowly Open the Valves to Add Water

Opening the valves gradually lets you control how quickly the pressure rises and avoids shocking the system.

• Open the first valve (often the one connected to the mains) fully or to the vertical position.
• Then slowly open the second valve (the heating side) a little at a time.
• Listen for water flowing gently and watch the pressure gauge.

Step 7: Monitor the Pressure and Stop at the Correct Level

Keeping an eye on the gauge stops you from adding too much water, which can cause high pressure problems or leaks.

• Stop when the gauge shows between 1 and 1.5 bar (aim for around 1.2 to 1.3 bar when cold).
• Close both valves tightly in the reverse order you opened them.
• If you have a detachable loop, remove and store it safely.

Step 8: Restart and Test Your Boiler

Bringing the system back online lets you check that everything is working again after repressurising.

• Turn the boiler back on at the isolator and controls.
• Reset any fault codes if needed following your manual.
• Turn the heating on and check that radiators start to warm up evenly.
• Keep an eye on the pressure over the next few days.

If the pressure drops again quickly after repressurising, there is likely an underlying issue such as a small leak on a radiator valve, a faulty pressure relief valve or a problem with the expansion vessel. In these cases it is best to get it looked at properly rather than keep topping up.

A good boiler cover plan means you do not have to worry about unexpected repair bills. It protects you when things go wrong and helps prevent small issues from turning into expensive ones.

Why Choose PlusHeat Boiler Cover for Your Glow Worm Boiler

Getting the right protection gives you confidence that your home heating system stays reliable all year round.

PlusHeat boiler cover plans are designed for busy UK homeowners and landlords who want straightforward, dependable support. With our cover in place you can call us out whenever your Glow Worm boiler needs attention without worrying about high repair costs. We help limit disruption and keep those heating bills under control by catching problems early.

Take a look at our boiler cover plans to find out more about the best option that suits you best. 

Frequently Asked Questions 

How often should I check the pressure on my Glow Worm boiler?

It is a good habit to glance at the pressure gauge once a month, especially before the colder weather starts. Many people only notice it when the boiler stops working, but regular checks help you spot drops early.

Can repressurising my boiler fix a leaking radiator?

No, repressurising only tops up the water level. If you have a leak you will need to fix that separately otherwise the pressure will keep falling. Bleeding radiators can sometimes help balance the system after you top up.

What should I do if the pressure keeps dropping after repressurising?

Repeated pressure loss usually points to a leak somewhere in the system, a dripping pressure relief valve or an issue with the expansion vessel. Get a qualified Gas Safe engineer to investigate rather than keep adding water.

Is it safe to repressurise my Glow Worm boiler if I am a landlord?

Yes, as long as you follow the steps carefully and the boiler is accessible. However many landlords prefer to have a professional service visit as part of their tenancy compliance and boiler cover to make sure everything is documented correctly.

Will repressurising affect my boiler warranty or service history?

Doing it yourself occasionally will not normally void the warranty, but always check your Glow Worm manual. Keeping a note of when you topped up the pressure is useful if you ever need to make a claim or arrange a service.