Yes, a leaking radiator can cause boiler pressure to drop if your home has a sealed heating system. Water that escapes reduces the amount in the system, so the pressure on the gauge slowly falls. It is not the only possible cause, though, so it helps to look at the wider picture.
How a sealed heating system loses pressure
Many homes, especially those with combi boilers, have a sealed system. It is filled with water and then pressurised, and the boiler shows this on a gauge. Because the system is closed, the pressure should stay fairly steady once it has settled.
If water leaks out anywhere, the pressure falls. A slow drip may only show up as a gradual drop over days or weeks. A faster leak can make the pressure fall quickly, and some boilers may stop working until the pressure is restored.
Radiator and pipework leaks to look for
Radiator valves are a common place for small leaks. Water can weep from the spindle, the nut that joins the valve to the radiator, or the joint to the pipe below. Corroded radiators can also develop pinholes, often along the bottom edge.
Pipework leaks can be harder to spot. Pipes run under floors and inside walls, so a leak may show as a damp patch, a ceiling stain or a warped floorboard. Around radiators, look for rust marks, damp carpet or crusty deposits on fittings, which can be a sign of an old drip that has dried.
Bleeding radiators also lets a small amount of water out along with the air. So it is normal for the pressure to dip a little after bleeding. If it keeps falling afterwards, there may be a leak.
Other causes on the boiler side
Not every pressure drop comes from a radiator. A faulty expansion vessel, which absorbs the extra volume of water as it heats, can make the pressure rise and fall. The pressure relief valve may then discharge water through a pipe, often to the outside. These parts are on the boiler side. The HSE explains that wet work on pipes and radiators does not need Gas Safe registration, but work on the gas boiler needs a Gas Safe registered engineer.
If your boiler needs repressurising, follow the boiler manufacturer’s instructions. Do not take covers off the boiler or adjust any of its parts yourself.
When to get the pressure drop assessed
It is worth getting help if you need to top up the pressure regularly, or if you can see water near a radiator or pipe. Finding a leak early can limit damage to floors and ceilings. A plumber can check radiators, valves and visible pipework for signs of escaping water. If you think a radiator is to blame, our page on fixing radiator leaks in Swindon explains how we can help with the plumbing side.
If your boiler pressure keeps dropping and you suspect a leak, Emergency Plumber Swindon can take a look at the radiators and pipework and talk it through with you. Call us on 01793 569521.