Boiler Leaking Water & Heating Faults
Fault codes, cold radiators, no hot water, what's safe to try and when to call.
A boiler leaking water is never routine
Unlike a dripping tap, a boiler that leaks is telling you a pressurised sealed component has failed, and the water is inside a cabinet full of electrics and a live gas appliance. Switch it off at the spur, turn off the water supply to it if you can reach the isolation valve, put a container underneath, and call. Do not run it "just for hot water" in the meantime.
Where the water is coming from tells you the cost
From underneath the boiler at a pipe connection, and it is often a joint that needs remaking, modest. From the pressure relief pipe, and the expansion vessel or the PRV has failed, still modest. From inside the case, running down the back, and it is usually the heat exchanger or the pump seal, that is the expensive one, and on a boiler over ten years old it is the conversation about replacement.
Pressure that keeps dropping is the same problem, hidden
A sealed heating system does not consume water. If you are topping up the pressure every few weeks, water is leaving somewhere, a radiator tail, a pipe under a floor, or out through the relief pipe on the external wall. Each top-up introduces fresh oxygenated water, which corrodes the system from the inside. It is the single most-ignored heating fault we attend.
What you can safely try yourself
Repressurising via the filling loop to 1.2 bar. Thawing a frozen external condensate pipe with warm water. Bleeding a radiator that is cold at the top. Checking the timer after a power cut. That is the complete list. Everything behind the case is Gas Safe territory, not because of gatekeeping but because the appliance burns gas and vents combustion products into your house.
When to stop and call the emergency number
If you smell gas, see soot or yellow staining around the boiler, or your CO alarm sounds: open the windows, turn the gas off at the meter, get everyone out, and ring the National Gas Emergency Service on 0800 111 999 before you ring anybody else including us. Nothing on the display is worth investigating past that point.
What the fault code is really telling you, what's safe to try, and when to stop.
Five checks that fix a surprising share of no-hot-water mornings for free.
Valve, spindle, tail or the panel itself, each one leaks differently, and only one of them means a new radiator.
A sealed system does not consume water. If you are topping up, it is going somewhere, and where matters.
Immersions, multipoints and wall heaters fail in predictable ways. What to check before replacing anything.
Sediment makes cylinders rumble, slows heating and kills elements. Flushing it is routine maintenance.
Where the water appears tells you how serious it is, from a loose fitting to a cylinder at end of life.
Worcester Bosch, Vaillant, Ideal and the rest: an installer's honest view of the brand question.
Cold at the top, warm at the bottom means trapped air. Ten minutes, one key, and the pressure check most guides forget.
Cold at the bottom and warm at the top is the opposite of an air problem, and bleeding it will not help.
Above 2.5 bar and the safety valve will dump water outside. The usual cause is the filling loop, not a fault.
No damp patch anywhere and the pressure still drops. The water is leaving, just not where you are looking.
Why is my boiler leaking water from the bottom?
Is a leaking boiler dangerous?
Can a leaking boiler be repaired or does it need replacing?
Why does my boiler lose pressure overnight?
Water where it
shouldn't be? Call.
A person answers, not a menu. You'll have an arrival time and a price range before you hang up.
020 3674 8514Or WhatsApp 07865 292684, photos help us bring the right parts
