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Overconsumption and cold radiators mean that the heating circuit is clogged with sediment. To find a successful installation, simply eliminate them with a chemical defogger kit.

disembowel radiators

The water flowing through the central heating installations is frequently acidic. Over time, this acidity leads to the oxidation of the metal walls of the pipes (steel, cast iron, aluminum...), radiators and / or heated floors.
This phenomenon results in the formation of insoluble particles that settle at the bottom of the radiators, in the underfloor heating tubes or in certain sensitive parts of the installation, such as the circulator.
These deposits can also generate noises in the network.
It is then the overall performance of the facility being degraded: some parts of the radiators or floor heating remain cold, pipes are clogged...

Defogging: a necessary treatment

To find an efficient installation and reduce the bill, a cleaning is required. It remains to be seen how to proceed.
Indeed, a simple rinsing with water is not enough. It is necessary to carry out a chemical cleaning or a hydropneumatic cleaning, generally carried out by a professional.
In the case presented here, the owners preferred the chemical solution because of its simplicity of use and its cost. The selected product is in fact in the form of a 3-in-1 maintenance kit (Geb) which includes, in addition to the de-scrubber itself, two other products: one to seal any microleakage caused by the sludge, the other to protect the installation of future agglomerates.
Note that these two complementary products have no effect if the heating network is not previously defogged.

Sludge treatment and a global solution

On the other hand, if the treatment is correctly implemented, it is particularly effective...
After the application of the three products, the network must be rinsed carefully.
This operation requires a very large volume of water and can be tedious if the purge of the heating circuit is removed from an evacuation: indeed, in the case presented here, nearly 600 liters of water were necessary for a network of 100 liters of capacity.

How much of the defoam product to buy?

how many bottles of defoam product use

In order for the treatment to be complete and lasting (5 years), it is imperative to correctly determine the quantity of defoamers to be used depending on the type of boiler, the number of radiators and the heated surface.
Otherwise, cleaning may be only partial and must be renewed in its entirety...

how much of the defatting product to buy

Purging or defogging: the tip of the heating engineer to slice

why a cold radiator downstairs

The temperature on the surface of a radiator must be uniform:

  • If it is cold at the top, it must be drained.
  • If it's his low part which is cold, it means that the radiator is clogged with sludge. (An infrared camera can be useful for measuring the importance of the problem.)

Preparation and treatment of radiators

open the cap of a radiator

Unscrew the cap at the radiator outlet to access the needle screw.
Screw tightly with a hexagon key to block the water drain.
Turn off the tap.

drain the radiators before defogging

Open the high purge of the radiator to drain (usually a little more than a liter of water).
A plastic bottle can be used as a funnel to collect water in a bucket.

purge radiators

Remove the high bleed plug with the adjustable wrench.
Insert the hose from the funnel (from the kit).
Slowly pour the defoamer.
If it is leaking, loosen the needle screw.

close the drain plug of a radiator

Replace and tighten the high purge cap, then open the radiator valve fully.
Top up the water in the heating circuit if necessary.

to restart a boiler during the deboning

Reset the circulation pump, set the boiler to a maximum temperature (80° C).
Let act 2 days
(5 days if you think the network is very bad).

Rinsing the central heating circuit

installing a drain valve on the central heating circuit

Install an automatic faucet nose for garden hose on the drain valve.

connection of a water tap to a central heating pipe

Connect a 15/21 male copper nipple and a female sleeve.
Seal with teflon.

completely drain the central heating circuit

Turn off the boiler, connect the garden hose to the automatic faucet.
Turn the knob on the valve to completely drain the central heating circuit.

Recovery of de-watering water

Collect water in a bucket (or a close look).
At the first emptying, it is dirty with a strong smell of scale.
Repeat the operation until it is clear.

Put back into service of the radiators

restarting the heating after defogging

After filling and reheating the circuit, isolate the radiator again.
Pour the clogging product into the high purge.
Set the boiler to 80° C.

pour a protective product into the central heating pipes

Wait 2 to 3 hours.
Empty one liter of water and add the protection product.
Engage the circulation pump.
Add product when upgrading the water circuit.

Practical DIY tips

  • Whichever method of defoaming is applied (chemical maintenance kit or hydropneumatic cleaning), care must be taken compatibility of the products used with the materials of the heating system, in particular aluminum (often present in condensing boilers).
  • In addition, do attention to effluent discharge.
  • They are supposed to respect the regulations in force...


Video Instruction: How to make a central heating power flusher with a submersible dirty water pump