For most boilers, between 1 and 1.5 bar when the heating is cold. Some manufacturers allow up to 2 bar. It's normal for the reading to rise a little when the heating is on.
Choose your boiler brand, then move the slider to match your gauge. You'll see that manufacturer's recommended range and what they say to do.
Recommended pressure when cold for most boilers boilers: 1.0 to 1.5 bar.
| Brand | Cold pressure | Source |
|---|---|---|
| Worcester Bosch | 1.0 – 1.5 bar | Worcester Bosch: boiler pressure FAQ |
| Ideal | 1.0 – 1.5 bar | Ideal Heating: Logic Combi troubleshooting guide |
| Glow-worm | 1.0 – 1.5 bar | Glow-worm: how to repressurise your boiler |
| Vaillant ecoTEC | 1.0 – 2.0 bar | Vaillant ecoTEC pro operating instructions |
| Baxi | 1.0 – 2.0 bar | Baxi: what should my boiler pressure be set at? |
| Vokera | 1.0 – 1.5 bar | Vokera Vision combi user, installation and servicing instructions |
| Viessmann | about 1 bar, top up to 1.5 bar | Viessmann: what to do if your boiler pressure is too low |
Your boiler will usually stop and show a fault code, such as Vaillant F.22, Ideal F1, Baxi E118, Glow-worm F.22 or Vokera A04. Topping up through the filling loop is a job your user manual covers:
If you overfilled it, bleed a radiator until the gauge is back in range, as Worcester Bosch and Baxi both advise. Baxi says the reading shouldn't go above about 2.5 bar even with the heating on. If it stays high after bleeding, call an engineer.
Worcester Bosch says topping up once or twice a year is normal. More often than that means water is escaping somewhere. Find a Gas Safe engineer to trace it.
Usually between 1 and 1.5 bar when the heating is cold, though some manufacturers allow up to 2 bar. Worcester Bosch, Ideal, Glow-worm and Vokera give 1 to 1.5 bar; Vaillant and Baxi give 1.0 to 2.0 bar. Your own manual has the exact figure.
Worcester Bosch says topping up once or twice a year is normal. If you're doing it much more often, water is escaping somewhere and you should contact an engineer or your installer.
If it's high because the system was overfilled, Worcester Bosch and Baxi both advise bleeding a radiator until the gauge is back in range. If it stays high, call an engineer.
No. A boiler with low pressure simply stops working and usually shows a fault code. Topping it up as your manual describes normally fixes it.