A boiler that keeps losing pressure can interrupt your heating and hot water and often leaves you topping it up more than you should. When this happens regularly, it usually points to something in the system that needs attention. By checking a few key areas, you can often narrow down the cause and decide what you can safely fix yourself before calling an expert.
Why is my boiler losing pressure?
When your boiler pressure drops, you usually notice the radiators warming slower than normal or see a pressure warning on the display. After topping it up, the pressure may fall again within hours or days. This repeated drop is a sign that something is not quite right. Some issues are simple to fix, while others need a qualified engineer.
Small Leaks Around Your Heating System
Small leaks are one of the most common causes of pressure loss, and fortunately, some are easy to spot and fix.
Look around radiators, valves, visible pipework, and under the boiler for moisture or staining. If a radiator valve is weeping slightly, tightening the connection can sometimes stop the leak. You can also replace the valve cap or washer if it is worn.
If the leak is coming from pipework or a joint you cannot reach, or you are unsure about tightening fittings, a plumber Milton Keynes or plumber Northampton can seal or replace the part quickly.
Repressurising the Boiler After Bleeding Radiators
If you recently bled your radiators, the system will naturally lose pressure. You can fix this by topping up the boiler using the filling loop. Most boilers need to sit between one and two bars when cold.
To repressurise it:
- Turn the boiler off.
- Find the filling loop (usually a silver braided hose).
- Open the valves slowly until the gauge rises.
- Stop when it reaches the correct level.
- Turn the boiler back on.
If the pressure falls again shortly after, there is likely another issue that needs investigating.
Issues with the Pressure Relief Valve
If the pressure relief valve is slightly open or faulty, you might see water dripping from the pipe that exits outside. In some cases, the valve gets stuck because dirt or scale builds up inside it.
You cannot fix this at home, but a plumbing service in Milton Keynes or plumbing services in Northampton can clean, service, or replace the valve to stop the water loss.
Expansion Vessel
If the expansion vessel loses its air charge, your boiler cannot stabilise pressure, which often causes it to swing up and down. When it cools, the pressure drops too low.
An engineer can fix this by recharging the expansion vessel with air or replacing it if needed. This is a common repair as part of boiler repair in Milton Keynes or boiler repair Northampton and is usually completed during the same visit.
Clearing Sludge and Internal Blockages
Internal sludge and corrosion can restrict water flow, create cold patches on radiators, and gradually cause pressure loss. This often needs a system flush to clear the debris.
A professional can carry out:
- A chemical clean
- A power flush
- Or install a magnetic filter
These solutions help protect your boiler long-term and stop pressure from dropping repeatedly. Plumbing services Milton Keynes and plumbing services Northampton carry out these treatments regularly.
Resetting the System After Repairs
Once the cause has been fixed, your boiler may still need to be reset or repressurised to return to normal. After any repair, check:
- Radiator valves are tight
- The pressure gauge stays stable
- There are no drips under the boiler
- Heating comes on evenly
If everything stays stable for several days, the pressure issue is resolved. If not, another test may be needed.
Need Help Fixing Boiler Pressure Problems in Milton Keynes, Northampton, Towcester or Wellingborough?
Able Plumbing Services provides expert boiler repair in Milton Keynes, boiler repair Northampton, and reliable support across Towcester and Wellingborough.
We can fix leaks, repair valves, recharge expansion vessels, and resolve any issue causing pressure loss. Fill out the contact form on their website to book your repair today.
