To repair a leak on a radiator, the ideal is to first understand how the device works. We will therefore first detail the operation of a radiator before considering the possible interventions to repair a leak.
The hot water radiator: operation and materials
Hot water radiators operate in a closed circuit. A boiler heats the water that circulates through the entire circuit to transport the heat. The diffusion is done by radiation in each radiator. At the end of the circuit, the water returns directly to the boiler where it will be heated again and reinjected into the circuit, etc.
There are two kinds of radiators: radiators low temperature inside which the water temperature does not exceed 50°C, and the radiators high temperature inside which the water temperature rises to 90°C.
The low temperature system uses steel radiators, which are less expensive but also less efficient, and aluminum radiators which are a little more expensive, but offer good performance for an affordable price.
Cast iron radiators correspond to the high temperature system. They have great inertia and take a little longer to reach the desired temperature.
Depending on the model, the radiators can be equipped with a simple manual valve (not thermostatic) which switches the radiator on or off. It regulates the flow of hot water to the radiator and therefore the room temperature.
A radiator can also be equipped with thermostatic valves which detect the ambient temperature and automatically adjust the water flow to obtain the desired temperature. These valves have sensors containing a liquid that expands in proportion to the ambient temperature.
Reflex number 1 to repair a leak on a water radiator: identify the leak area
Two areas can pose a leak problem:
- either the radiator valve is leaking,
- or it’s the supply pipe.
Indeed, over time, materials wear out and temperature changes put the various parts making up the radiator to the test, due to the phenomena of expansion and contraction of the materials. The seals can therefore be damaged and the nuts loosen.
The leak is on the radiator valve
First turn off the water supply.
Remove the plastic head (by loosening the screw in the center) when it is a single valve, or remove the entire thermostatic valve system.
Tighten the cable gland.
At the end of this operation, there should be no no drop of water. Don’t hesitate to wait a full hour to make sure there are no more leaks before replacing the head on the faucet.
If the leak is still present, the complete dismantling of the valve will be necessary to replace the seals and put back the tow (tow and sealant). It is then necessary to drain the top of the radiator concerned beforehand.
Once the tightness of the radiator has been found, bleed the radiator to remove the air which entered during the leak or the emptying and which risks damaging the boiler.
Complete the repair by replacing the faucet head.
The leak is on the radiator supply pipe.
Shut off the water supply and close the radiator supply valve.
You can then try to tighten the nut.
If that doesn’t work, you can do a temporary repair plugging the leak.
A permanent repair requires the complete emptying of the system as this alone will allow you to disassemble and change the connection made between the pipe and the radiator.
In this case, you might as well take the opportunity to improve your installation and place thermostatic valves on your radiators if this is not already the case. You will gain energy and comfort.
The tricky part of the operation consists in refilling the system with water at the good pressureotherwise the boiler may break.
If you do not feel able to do such an intervention yourself, call a plumber.