Boiler & heating breakdowns
Worcester Boiler Pressure Too Low: How to Top It Up
Published
To fix low pressure in a Worcester boiler, let it cool, then top up through the filling system underneath until the gauge reads just over 1 bar, up to 1.5 bar. Worcester fits three types: a keyed filling link, a blue keyless lever or an external hose loop. Needing this more than once or twice a year usually means water is escaping.
Is your Worcester pressure actually too low?
Look at the gauge with the heating off and the system cold. Worcester Bosch asks for between 1 and 1.5 bar on the gauge when the system is cool. It will climb a few tenths of a bar while the boiler is running, which is normal. Below 1 bar it needs topping up. Below 0.5 bar, in the red on most Worcester gauges, water has been lost and the boiler may stop.
Most Greenstar models have a round dial gauge on the underside or front panel. Some newer models also show system pressure on the display. When the pressure is too low, recent Greenstar boilers commonly show the fault CE 207 and stop heating until it is corrected.
Always read it cold. A reading of 0.8 bar with the radiators hot means it will be lower still in the morning.
Which filling system does your Worcester have?
Worcester Bosch has used three ways of letting mains water into the heating over the years. Crouch down and look under the boiler before you touch anything. The top-up steps are different for each.
- A blue lever beneath the boiler on the right, behind the removable bottom panel: the keyless filling link, found on many recent Greenstar combis
- A filling link beneath the boiler on the right with a white knob, worked by a separate plastic key that Worcester stores in the removable bottom panel: the keyed filling link
- Two small valves on the pipes below the boiler, joined by a silver braided hose, or with the hose missing: an external filling loop
If you have a keyed filling link but the key has gone missing, see our guide to topping up a Worcester without the key rather than forcing the port with a screwdriver.
How to top up the pressure on a Worcester boiler
Turn the heating and hot water off and give the boiler an hour to cool. Have a towel ready, because a few drops of water from the filling point is normal. Then follow the steps for your type.
Blue keyless lever: pull the blue lever down and hold it. Watch the gauge climb. Release the lever as soon as it reaches 1 to 1.5 bar and it springs back to shut the water off.
Filling key: push the key firmly into the filling link with the arrow lined up to the open padlock symbol, then turn it right to the stop so the arrow points at the closed padlock. Turn the white knob to the left and water starts to flow. When the gauge reads 1 to 1.5 bar, turn the white knob back to the right without overtightening, turn the key left to the open padlock and pull it straight down. Put the key back in the bottom panel so you will find it next time.
External hose loop: if the hose has been removed, screw it onto both valves first. Open the valve on the cold mains side, then slowly open the second valve on the heating side. Close both when the gauge reads about 1 to 1.5 bar, then remove the hose. Under the Water Supply (Water Fittings) Regulations 1999 a temporary filling loop should be disconnected after use, so that heating water can never flow back into the drinking supply.
Once the pressure is right, press the reset button once if the boiler is showing a fault code or a flashing blue light, and turn the heating back on.
If the needle goes above 1.5 bar, you have overfilled it. Worcester Bosch advises bleeding a radiator until the gauge is back between 1 and 1.5 bar; do it a little at a time with the heating off. Never open the boiler casing.
What if the pressure will not go up?
If the gauge does not move when you pull the lever or turn the key, check the simple things first. The main stopcock may be off or only partly open, which is common after a plumber has worked elsewhere in the house. Run the kitchen cold tap to check there is a good flow of mains water. A Worcester filling link needs reasonable mains pressure to push water into a heating system that is already pressurised.
After that, the filling link itself can be at fault. The keyless link is a small assembly with a check valve inside it, and scale can stop it opening or closing properly. It can be replaced as a spare part, but it sits partly inside the casing and should be changed by an engineer. Our page on a filling loop that is not working covers the other causes.
Why does my Worcester boiler keep losing pressure?
Worcester Bosch says a system usually needs topping up once or twice a year. If you are doing it every week or two, water is getting out.
Start with the copper pipe that runs from underneath the boiler to the outside wall. It comes from the pressure relief valve, and drips or a stain below it mean the valve is opening or passing. Then check every radiator valve and towel rail with a piece of kitchen roll. On Greenstar combis, the keyless filling link itself can weep at its joints, so look underneath for a drip there too.
If the pressure rises a lot when the heating comes on and falls back lower each time, the expansion vessel inside the boiler has probably lost its charge. A rise of a few tenths of a bar between cold and fully hot is normal; a much bigger swing, especially one that takes the needle towards 3 bar, suggests the vessel needs checking and recharging by an engineer. Our guide to pressure dropping every day shows how to test which it is.
When to call an engineer, and what it costs
Call someone out if the pressure drops back below 1 bar within days of topping up, if the relief valve pipe keeps dripping, if water is coming from under the boiler or if the boiler shows CE 207 again straight after a reset. Those faults are inside the casing or in the pipework. Our Worcester boiler repair visit covers them. If it is the pressure alone rather than a wider Worcester fault, see boiler pressure repair.
An engineer checks the expansion vessel charge, the relief valve, the filling link and the internal joints on the pump and hydraulic block. Gas work is carried out by Gas Safe registered engineers. The £60 call-out applies at any hour, and the repair price is agreed with you on site before any work starts. Typical UK market prices are about £90 to £200 for a relief valve and £150 to £350 for an expansion vessel. If the boiler is still under its Worcester guarantee, check the terms before booking anyone, as the manufacturer may need to do the repair.
Questions people ask
What pressure should a Worcester boiler be?
Between 1 and 1.5 bar with the heating off and the system cold, which is the range Worcester Bosch gives. It rises a little while the boiler is running, which is normal.
Where is the filling key on a Worcester boiler?
On keyed Greenstar boilers it is a plastic key that Worcester Bosch stores in the removable panel underneath the boiler. It fits into the filling link beneath the boiler on the right. If it has gone, Worcester can supply a spare.
Why is there no blue lever or key on my Worcester?
Your boiler probably uses an external filling loop: two valves on the pipes below it and a braided hose. The hose is often removed after installation, so look for two small valves with screw ends.
How often should I top up my Worcester boiler pressure?
Once or twice a year at most, according to Worcester Bosch. More often than that means water is leaking out and the cause should be found.
Is it normal for water to drip when I top up a Worcester?
A few drops from the filling point while you top up is normal. A drip that carries on after the lever or key is closed means the filling link is passing and needs looking at.