How To Maintain a Gas Water Heater


Structurally, all gas water heaters are divided into instantaneous and storage. Both types have been performing their functions for decades. However, over time, a decrease in efficiency inevitably occurs. If nothing is done, the heater will simply fail. The most common cause is the settling of combustion products and the accumulation of lime deposits. Therefore, it is important to perform periodic maintenance on your gas water heater.

Time to clean

It is recommended to clean gas heaters every one to two years. It all depends on the degree of water hardness in the home or main water supply, as well as on the frequency of use of the water heater. Not all users follow the manufacturer’s recommendations – and this is completely in vain. Here are the most common consequences of a clogged gas water heater.

  • Does not turn on or goes out quickly after ignition. The reason is the accumulation of a large amount of soot on the injectors or igniter.
  • Thermal protection is triggered. The water heater gives a signal about overheating, which indicates that the cooling system is clogged or scale has accumulated on the walls.
  • A drop in hot water pressure compared to cold water pressure indicates a clogged pipeline inside the water heater. Salts deposited on the walls lead to a drop in throughput.
  • The appearance of a burning smell in the room or smoke in the space at the installation site indicates that the smoke exhaust system is clogged with soot and combustion products.

Removing scale from heat exchanger pipes

This procedure is relevant for instantaneous gas water heaters. There, the heat exchanger consists of a system of pipes exposed to the burner flame. Due to the presence of dissolved salts in water, heating leads to intensive deposition of a limescale layer on the walls of the pipes. The amount of deposits is conventionally divided into light, medium, and heavy. The first two types can be easily removed, even at home.

Only chemical cleaning of the heat exchanger is allowed. Both folk remedies and specialized formulations are suitable here. Most manufacturers indicate an acceptable list of such products in the instructions.

The home removal process consists of the following steps.

  • Shut off the gas supply to the dispenser. You should also turn off the cold water tap at the inlet to the gas water heater. If gravity flow from another mixer through the hot water system is possible, then you need to turn off the hot water tap on the water heater. 
  • Remove the front panel from the gas water heater, unscrew the heat exchanger from its mounting points, and remove it from the wall. The water needs to be drained from it.
  • Using a hose with an expansion tank or a rubber bulb, pour the solution into the heat exchanger. The entire structure sours within two to three hours. If plaque hardens, the solution can be left overnight. Additionally, the heat exchanger can be placed in a container with a solution. The manufacturer, as a rule, indicates the duration of use of chemicals.
  • Remove the solution from the instantaneous water heater tubes and rinse the part with clean water. 
  • Connect the heat exchanger to the stationary mounting points and assemble the entire structure in the reverse order. Do not forget to install gaskets at the pipe joints (replace if necessary).

Then open the gas and water supply from the system. Test the operation of the installation after cleaning. At first, the pressure will probably not be very strong: the water will wash away the remaining scale.

Particularly dense scale deposits are not always removed using this method. Here special devices that create solution pressure inside the pipes will come to the rescue. This operation can only be performed by qualified specialists.

Anti-scaling storage boiler

Due to the constant presence of water in the tank of a gas storage water heater, dissolved salts have a much more intense effect on the inner surface of the tank. This leads to the destruction of the metal, breaks the seal, and can cause a leak.

To protect the water heater tank, a magnesium anode is installed in it. It should be changed every one to two years. To do this, first purchase a new anode of the appropriate size. The replacement process consists of the following steps.

  • Turn off the gas supply to the boiler and close the hot water tap.
  • Unscrew the magnesium anode from the tank and install a new one (selected by the manufacturer’s instructions).
  • If the gasket under the anode has become unusable, it should be replaced.

To remove the scale, the walls and container of the tank must be washed with one of the above solutions. First, tap water is removed. The tank is looped through a separate pump and thoroughly washed. The duration of flushing depends on the volume of the boiler and the performance of the compressor. This work is performed by qualified specialists using special equipment.

It’s difficult to clean – it’s easier to prevent

The main reason for the accumulation of plaque on the walls of pipes is salts dissolved in water. They actively crystallize at temperatures from +70 °C and above. Forced water softening can eliminate the need for annual cleaning and increase service life. This is done by installing a filter. What are they?

  • A coarse filter is a metal mesh, usually installed at the entrance of the water supply line to the home. Allows you to trap the largest particles.
  • Softening filter – made in the form of a flask or tube. Installed in front of a gas water heater. Water flows through special crystals, and due to a chemical reaction, its hardness is reduced. 
  • Magnetic filter – represented by a pair of magnets that create a field in a certain section of the pipe. Water passing through the field modifies the structure of dissolved salts. As a result, they can no longer be deposited on the walls of the pipes or tank.

Cleaning from combustion products

When gas burns in the chamber, heat, and combustion products are released. They settle on the walls in the form of soot. The amount of soot and its consistency directly depends on the quality and chemical composition of the gas. Bottled fuel smokes heavily. The blockage from the main gas mixture can be so insignificant that the soot, in principle, will not make itself felt.

Clogging of the chimney, combustion chamber, and surrounding elements differs in each specific case. It all depends on the surface and coating material, the presence of pipe bends, and the angle of rotation. Soot acts as thermal insulation. Therefore, when there is an excess of it, in addition to poor smoke removal, weak heating of the water is observed. To remove combustion products, screwdrivers, hooks, soft and hard brushes, and a vacuum cleaner are used.

Cleaning the chimney from soot

The chimneys of gas water heaters differ in their length. In small smoke exhaust systems, cleaning can be done with a regular brush. Long pipelines (for example, in private houses) require the use of special devices.

To clean the chimney, be sure to clear some space around the boiler. Remove dishes and other kitchen utensils that can easily be stained with soot. Use old clothes or special “work” clothes. You may need a container to collect soot.

Corrugated elements and pipeline bends are the most susceptible to clogging. These are the ones you should focus on.

  • Disconnect the flue pipe from the gas water heater. In some models, it is enough to lift the pipe with your hands; in others, this will require a plumbing tool.
  • If free access with a brush is blocked by filters or fastening parts, remove them.
  • If possible, place a container under the chimney to collect soot and use a brush in a circular motion to clean the pipeline.

Upon completion of the work, check the permeability – just bring a burning match inside the chimney, it should burn with an even flame. Straight sections of the pipe can be checked for light transmission.

Cleaning soot on internal elements

The chamber with nozzles, igniter, and coil grille in instantaneous water heaters are the most clogged with soot.

To remove soot, remove the housing cover and open the combustion chamber protection. Cleaning is performed in the following sequence:

  • Turn off the gas supply and lift the burner from its place of fixation.
  • Using a vacuum cleaner, remove soot from the surface of the chamber, around the burner, and from the fins of the coil.
  • If there is carbon deposits that cannot be removed with a vacuum cleaner, remove the deposits with a metal brush. Be careful not to disrupt the gas supply.
  • Remove the cleaned carbon deposits with a vacuum cleaner or a damp cloth (not lint!). 
  • If fumes block the nozzles, clean them with a metal hook.

In storage gas water heaters, the cleaning principle is different due to the absence of a coil. Instead, there is a flame tube above the burner.

Based on the type of combustion chamber, all models of gas boilers are divided into open and closed. The former uses natural ventilation, the latter forced. Water heaters with an open chamber clog faster. Cleaning of soot and carbon deposits is carried out in the same way as with flow-through models. 

Cleaning the igniter

This is done in cases where the water heater does not ignite and there is no characteristic sound of an electric arc. This indicates soot accumulation on the igniter. To clean, you will need to disassemble the case and remove the protective cover. Disconnect the thermocouple and brush the surface with a soft brush – harsh operations can damage this part.

If necessary, the igniter can be removed from its installation location to wash and remove accumulated soot. Upon completion of cleaning, it is installed in its original place in the reverse order.

In conclusion

A gas water heater can be cleaned either with the help of qualified specialists or independently. But in the latter case, all work must be carried out in strict accordance with the operating instructions.

To remove scale, be sure to use products that are approved for your water heater model. Whatever properties the solution has, for certain coatings its effect can be detrimental. 

In large-volume storage gas models, it is recommended to install a membrane-type expansion tank. It allows you to level out excess pressure during the thermal expansion of the liquid. This will increase the life of the boiler. 

The cold water intake unit must also be periodically cleaned of lime deposits. The water intake unit is represented by a rubber membrane that traps small solid particles.

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