Your boiler keeps losing pressure: what it means

What counts as normal pressure for your boiler?

There is no single figure that is right for every boiler and every system. Manufacturers state the pressure that suits their appliance when the system is cold and when it is warm.

Check the manual for your own boiler and note the figure it gives, so you can judge later whether the reading is genuinely off.

Topping up: only as the manufacturer describes

Some appliances have a filling arrangement the householder may use; on other systems that is not the case.

Only top up if the manual describes it, and follow those steps exactly. If you are unsure, leave it to an engineer.

Can you see water anywhere?

If you find a leak, do not attempt a repair yourself; have it assessed. A small leak can cause damage over time.

• Look for damp patches or limescale under or beside the boiler.
• Check radiators and visible pipework for wet spots or rust marks.
• Watch for stains on ceilings or floors where pipes run out of sight.

Frequent pressure loss is not routine

If you need to top up every week or every month, that is a fault rather than maintenance. Water is being lost somewhere, or the expansion vessel can no longer absorb the pressure.

Repeated topping up puts extra strain on the system, so it is better to have the cause investigated.

What a service covers

During a service we look at water pressure, the expansion vessel and visible connections, so recurring pressure loss often comes to light before it becomes a breakdown.

When is a professional check needed?

• You regularly have to top up to keep the pressure steady.
• The pressure drops again within a day of topping up.
• You see water, rust or limescale at the boiler or pipework.
• The boiler shuts itself down because the pressure is too low.