Water leaking underneath your boiler is commonly caused by high boiler pressure, loose pipe connections, worn pump seals or a faulty pressure relief valve. In some cases, the leak may come from inside the boiler itself, which should always be inspected by a Gas Safe engineer. If your boiler is also losing pressure, read our Boiler Losing Pressure guide for additional troubleshooting.
A small drip isn't always an emergency, but a leaking boiler should never be ignored. If water is reaching electrical components, the leak becomes severe or you notice the smell of gas, switch the boiler off immediately and arrange a professional inspection. Continuing to use a leaking boiler can lead to more extensive damage and higher repair costs.
Yes. Excessive pressure can force water through the pressure relief valve, causing your boiler to leak. Most boilers operate best between 1 and 1.5 bar when cold. If your pressure repeatedly rises above the recommended level, there may be a fault within the heating system that should be investigated.
Pressure loss and leaks often occur together because escaping water reduces the pressure inside your heating system. The cause could be a damaged valve, leaking pipework, a faulty expansion vessel or an internal boiler fault. If you regularly need to top up the pressure, it's important to identify the source of the leak rather than repeatedly repressurising the boiler.
Boilers can leak from several different locations, including the pressure relief valve, pump seals, internal pipework, heat exchanger, condensate pipe or nearby heating connections. Identifying where the water is coming from can help determine whether it's a simple repair or a more serious internal fault.
You can safely check visible pipework, monitor the pressure gauge and dry the area to identify where the leak is coming from. However, internal boiler repairs should only be carried out by a Gas Safe registered engineer. Attempting to repair gas appliances yourself can be dangerous and may invalidate your boiler warranty.
The cost depends on the cause of the leak and whether replacement parts are required. Simple repairs such as replacing seals or valves are generally less expensive than repairing a damaged heat exchanger or pump. Keystone provides clear, transparent quotations after diagnosing the fault, so you'll always know the cost before any work begins.
Yes. Keystone provides fast boiler leak diagnosis and emergency boiler repairs throughout London. Whether your boiler is leaking underneath, losing pressure or has stopped working completely, our experienced Gas Safe engineers can quickly identify the problem and recommend the most effective solution.
If your boiler is leaking and has stopped working, switch it off if the leak is significant or near electrical components. Avoid repeatedly resetting the boiler or increasing the pressure, as this may make the problem worse. If you have no heating or hot water, our No Heating and No Hot Water guides explain a few safe checks you can carry out before booking an engineer.
Keystone provides professional boiler repair services across London, helping homeowners resolve leaks quickly and safely. Our Gas Safe engineers diagnose the cause of the leak, explain the available repair options and provide transparent pricing before any work begins. Whether your boiler is leaking, losing pressure or displaying fault codes, we're here to restore your heating with reliable, long-lasting repairs.