Boiler · Naples and Campania
Boiler leaking water: where it comes from and what to do
A boiler that leaks water should be taken seriously, but without panic: the leak is almost always visible from underneath and leaves clear clues. First put a container under it, dry the area and see where the drop falls from. On a video call a few shots are enough to tell whether it is a drain pipe, a fitting or the boiler itself from the inside.
From €110 + VAT about 1 hourCleaning, flue gas check and logbook. Compliance sticker (bollino) is extra
If the water gets near sockets, the plug or the boiler cables, switch off the boiler switch or the main trip switch before drying up. Do not open the casing to look for the leak and do not tighten fittings at random: under the boiler the gas pipe and the water pipes look alike.
Recognise the problem
- Drops or a puddle on the floor under the boiler
- The drain pipe under the boiler drips, especially when it heats
- The pressure rises a lot when the boiler is on
- You have to top up the system often
- You see white crusts or rust on the fittings
- Water comes out of the small condensate pipe
The most common causes
- 1
Safety valve discharging
When the pressure goes over the limit, usually because of a discharged expansion vessel, the safety valve lets water out of its pipe. The valve is doing its job: the reason for the high pressure has to be found.
- 2
Fittings and gaskets
Under the boiler there are several connections with gaskets that harden over time. A slow drip from a fitting is the simplest case to repair.
- 3
Condensate drain
Condensing boilers produce water from the flue gases and send it to the drain through a small pipe and a little trap, a bend that holds water. If it clogs or comes loose, the water ends up on the floor.
- 4
Perforated heat exchanger or leaking pump
With age and limescale the heat exchanger can perforate, or the pump can leak from its gasket. Here the water runs from the inside and the boiler has to be opened.
What you can safely check yourself
- Put a container under the leak and dry the area well, so you can see where the first drop falls from.
- Read the pressure with the boiler cold and then after half an hour of running, and note the two values.
- Photograph the pipes under the boiler, with the drop clearly visible if you can.
- If you have lost a lot of water and the pressure is low, top up from the filling valve to the manual value while waiting for the technician.
Never open the boiler or the gas water heater, and always switch off the power before touching an electrical appliance. If in doubt, call us.
When you need a technician at home
- Water runs from inside the boiler or from the bottom of the casing
- The safety valve discharges every time the boiler heats
- With the boiler hot, the pressure gets close to 3 bar
- The leak is near the electronic board or the cables
How much it costs
Boiler service and flue gas analysis (our price)
Cleaning, flue gas check and logbook. Compliance sticker (bollino) is extra
from €110 + VAT
Repair of a boiler leak
indicative market price in the Naples area; a gasket costs much less than a heat exchanger
40-250 €
Market figures are indicative for the Naples area. You know our exact price before we start; prices apply near our base in Parete, and further away you see them in full when you choose your town.
Where the water comes from: how to read the clues
If the pipe leaving the bottom of the boiler towards the drain is dripping, it is almost always the safety valve. Look at the pressure: if it rises a lot when hot, the expansion vessel has lost its charge and the valve discharges the excess.
If the water is small in quantity, slightly cloudy and falls from the little plastic pipe, it is condensate. In condensing boilers it is normal to produce it, but it has to end up in the drain and not on the floor.
If the drop is on a fitting, with a white crust around it, it is a gasket. If instead the water runs from the bottom of the casing with no precise point, the leak is inside: heat exchanger, pump or an internal pipe.
Boiler leaking water with high pressure
High pressure and a leak often go together. The expansion vessel no longer absorbs the expansion of the hot water, the needle rises towards 3 bar and the safety valve opens.
Topping up the system in this situation does not solve it: when cold the pressure drops, but it rises and discharges again as soon as the boiler runs. The remedy is to recharge the vessel with air or replace it, a job done by opening the boiler.
If instead the filling valve does not close properly, the pressure rises even with the boiler off. This too is easy to see on a video call: the needle moves slowly with everything stopped.
Want to know what it is first? Show us
You show us the pipes under the boiler and the pressure, and together we work out where the water comes out. If it is the safety valve discharge or the condensate, identifying the cause is often enough. If it leaks from the inside you need a home visit, and we arrive knowing what to look for.
Video consultation, up to 15 minutes: €9.90 (€14.90 on Sundays), deducted from the bill if we then come to your home.
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Frequently asked questions
The boiler leaks water from underneath: can I keep using it?
If it is a slow drip from a fitting and the pressure holds, you can use it with a container underneath while waiting for the technician. If it leaks a lot, if water reaches the cables or the pressure collapses, switch it off and close the main water valve of the house.
Why does it leak water from the safety valve?
Because the pressure goes over the limit, often because of a discharged expansion vessel, or because the valve has got dirty with limescale and no longer closes. In the first case the vessel is fixed, in the second the valve is replaced.
Is condensate water normal?
Yes, in condensing boilers water forms from the flue gases and it is meant to go to the drain. It becomes a problem if it comes out of the small pipe and ends up on the floor, because of a clogged trap or a disconnected pipe.
How much does it cost to repair a leaking boiler?
It depends on what is leaking. On the Naples market repairs usually fall between 40 and 250 €, and a gasket sits at the lower end. After the diagnosis we give you the exact price, before we start.
Is it worth repairing if the heat exchanger is perforated?
On a recent boiler usually yes. On a very old boiler we assess with you whether it is better to replace the part or the boiler, working out the numbers together.
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