How to drain all the water from a boiler

Users often wonder when to drain the storage water heater?

To formulate a simple rule of thumb. cream when you can’t do the procedure without it. In other cases it is not.

Know that the boiler is sensitive, so you should not break its usual rhythm of work by emptying it for no reason.

So, it is necessary to drain the water heater:

  • If the device is left in a cold room for a long time. For example, you definitely need to drain the water heater for the winter. Otherwise, it will freeze and rupture the boiler;
  • After the warranty time, when you yourself clean the boiler, the heating element from scale, change the anode or make repairs.

There is no need to empty the tank if:

  • You plan not to use the device for a long time, but it stays in a heated room or where the temperature is at least 5C;
  • The full heater has been standing unplugged, and now you need to remove the water. It is better to drain the liquid naturally by opening the faucet;
  • The warranty period has not expired. Use the help of a craftsman. If in the process the device breaks down through your fault, its repair will not belong to the warranty cases, therefore, it will not be repaired for free.

The design of the water heater is quite simple. The tank is a vessel for heating water. Inside the device there are heating elements. heating elements themselves. The supply of hot water to the outlet and tap water to the inlet is through a system of valves. The latter serve as a protective system, for example, do not allow you to completely drain the water, so that if a sudden disconnection of cold water heating elements do not burn out.

It is impossible to rule out the possibility of overheating and burning of the heating elements. Therefore, the recommendations in the operating manual usually indicate that the water from the boiler under normal circumstances can not be completely drained. If the tap water was disconnected for technical reasons, before start-up you should check whether there is enough liquid in the tank.

There are a number of situations in which it is necessary to drain the water from the heater.

  • The boiler is installed in an unheated room and will not be used for a long time. In severe frosts, the liquid in the tank can freeze, and this threatens the deformation and destruction of heating elements and housing. Drain the liquid from the water heater and the entire system serving it.
  • When making repairs and cleaning, preventive inspection. As a rule, it is necessary to use special techniques to drain the water, because the design does not provide complete emptying of the tank.

There are other circumstances that raise doubts. In most of them, the liquid is not drained.

  • If the boiler is turned off for a long time, for example, for the winter, hot water can be obtained from the heating system, but the unit is in a heated room, it does not need to be emptied. It is enough that the room where the tank is located maintains a temperature above 5C.
  • If the water heater stands with water for a very long time, the liquid stagnates in it. It is undesirable: it smells bad, may contain impurities. But there is no need to drain it: simply open the tap and let 100 liters of water flow through. This procedure is performed once every 3 months in order to clean the tank and preventive maintenance.
  • If the device needs repair, but the warranty is still valid, do not disassemble or even clean the device yourself. So in this case, the water is not drained until the arrival of a specialist.

Emptying the tank is contrary to its normal mode of operation. Therefore, you should do it only for a real good reason.

What is the threat of downtime

Disputes about the need to empty the water heater is usually associated with a lack of knowledge of the instructions. The most common explanations are as follows.

    If you leave the water in the tank, it will go bad, it will get pathogenic bacteria in it. this is actually unlikely. Liquid in the tank is already heated to 60-80 ° C, and at this temperature very few bacteria survive. For cooking or drinking this liquid is not used, so that even with a stale odor can not harm your health. The 100 liters of tap completely displaces stagnant water.

Modern models often have special coatings. anti-corrosion, antibacterial. Such a tank is not at risk.

General rules for disassembly and flushing

Before removing scale deposits, remove and wash the rubber gasket located between the tank and flange.

After scooping out the sludge with a scoop (easy to make from a plastic bottle), wash the container:

  • Wash the inside of the tank with a hose. Run the liquid through in stages so that it can push out the sediment from the bottom.
  • After rinsing the tank interior treat with vinegar or lemon solution to remove the odor. Use a long stick with a rag tip for this purpose.
  • Clean the FET. First carefully clean the heater by hand with a knife or screwdriver, removing the easily removable plaque.
  • Anything that can not be removed, remove by soaking the heating element in citric acid or vinegar solution. Make a hole in the plastic bottle with a slightly larger cross section than that of the heating element. Pour hot water and add citric acid or table vinegar. Let it stand for 24 hours, occasionally shaking the limescale dissolving agent or filling with fresh water. After a day remove the heating element and remove softened scale by means of a wooden or plastic shovel.
  • Carefully inspect the heating element and magnesium anode. If you find even small signs of damage, install new elements.

After draining or subsequent cleaning work, the device should be assembled in reverse order and perform water start-up. This is done before turning on the power grid to check the unit for leaks.

Briefly about the construction of the boiler

Before you start draining the water, you should study the structure, design and operation of the boiler. Such information is usually found in the manual for the water heater. Let’s consider in detail what is a boiler and how it works.

The main structural part of the boiler is a storage tank, made of metal: stainless steel or ordinary steel with an enamelled coating on it. The tank is equipped with two tubes, an air vent and an electric heater. To keep the water in the tank at a high temperature for a long time, the tank is insulated with a layer of thermal insulation material. This entire structure is enclosed in a single body, and for the boiler to work in automatic mode, the device is additionally equipped with a thermostat.

Boilers come in different capacities. In small water heaters, as a rule, there is no drainage hole, and the water is fed from above. Drain the water from the tank is easy enough, the tank should only be removed and turned upside down.

Tip: Choosing a water heater with a small volume, assess the convenience of the device and give preference to those models, the draining of which will not be difficult.

Capacious boilers are often equipped with a drainage hole, but emptying such heaters is more difficult than in the above case. If you simply close the access of cold water in a container, and then open the tap for hot water drain, the liquid will not run out completely, but only to the level where the highest point of the hot water pipe. You can fully drain the water only if the air enters the boiler. For draining large water heaters, the inlet and outlet ports of the structure are equipped with tees with taps.

Schematic representation of the internal structure of the boiler

When the water heater must be drained

So that a person does not doubt whether it is necessary to drain the water from the tank or you can do without this procedure, it is necessary to clearly define the problem that has arisen. Many manufacturers of water heaters do not recommend leaving the device without water for a long time because of the danger of corrosion of metal parts.

Obligatory need to drain the water occurs in three cases:

  • Obligatory water drainage is required for a water heater installed in a country house. The question of how to do this arises with the owner at the end of the season. If the water is not drained for the winter, the liquid will freeze and rupture the accumulation tank of the water heater at subzero temperatures. The problem does not affect owners who live year-round in a vacation home.
  • The need to drain the water occurs when the water heater breaks, as well as preventive cleaning of the tank from limescale and dirt. The frequency of scheduled maintenance depends on the design of the appliance, as well as the quality of the liquid. The harder the water is, the faster the scale builds up. However, on dry heating elements solid deposits are deposited longer than it happens with devices with open heating elements.
  • You can’t do without flushing in an apartment in case of a plumbing breakdown. From a storage tank designed for 80 or 100 liters, you can take the liquid for technical needs: flushing the toilet, washing hands and other purposes.

If, according to the instructions, the device is not designed for long downtime without water, then in case of plumbing failure, you can try to find another solution to the problem. As an alternative, purchased bottled water can be helpful.

It is not necessary to empty the storage tank in the cottage when the owners are away. Although, here you should consider the duration of absence, the peculiarities of the design of the heater, the minimum temperature inside the room and the source of water intake. And now about everything in order:

  • If a long departure from the dacha falls in the winter, then in severe frosts, the temperature inside the room will drop to a negative mark. No matter how destructive the lack of water is to the device, the liquid must be drained.
  • Inside the room, where the air temperature does not fall below 0 o C, the stainless steel tank is better not to empty. There is less corrosion in the presence of water.
  • It is better to empty appliances with copper heaters when not in use. Here the corrosion process happens in the opposite direction. Copper degrades faster in water with a higher hardness.
  • Prolonged water heater downtime is dangerous for the emergence of infection. Stale water begins to rot, which can be recognized by an unpleasant smell. It’s quicker when the water heater is recharged from a home well.
  • The water in the central water supply system is chlorinated, which destroys the putrefactive bacteria. If you leave the boiler unplugged for a week, the likelihood of rotting is minimal.

In general, it is not necessary to empty the tank of the water heater when leaving the cottage for a short period of time. Stale water can simply be drained and a couple of times heated to maximum temperature.


Always take precautions before draining the water from the boiler:

  • Turn off the power and let the water cool down. Agree, pouring boiling water. it is not only uncomfortable, but also dangerous, because you can get burns. If you plan to drain the water in the morning, then turn off the water heater at night.
  • Perform all work only with the plug unplugged from the socket. De-energize the boiler before you perform any operations on it.
  • Do not remove a water-filled boiler, as it is difficult and the process of draining the water can be difficult.
  • Shut off the cold water supply with a special faucet, otherwise you will never achieve complete emptying, since the principle of the boiler allows it to issue hot water, while pumping cold water.
  • Find a container where the water will be drained and prepare it in advance.
drain, water, boiler

How to drain the water heater?

Households that do not reside in the cold season should have annual engineering work done to prepare the water heating systems for the winter period. In this case, it is useful to know some peculiarities of technology and the use of devices for water heating, so that during the draining of the liquid does not arise difficulties.


The process of draining water from boilers of different manufacturers is almost identical, except for some nuances. Before emptying the Thermex water heater, it is recommended to perform some preparatory actions. First of all, the device is disconnected from the mains. This measure is necessary for safety reasons, otherwise the equipment could fail and the person working with it will be injured.

And you also need to shut off the water taps in the house so that the water does not flow into the tank. Leave the appliance untouched for a moment to allow the water in the tank to cool down.

As previously mentioned, Thermex boiler models vary in shape and size. Flat appliances of large volume are equipped with two holes for water supply and outflow, to which are connected pipes. Before draining this type of appliance, the tubes must be removed. Thermex small volume and rounded shaped water heaters work on a different principle. To empty this type of device, it is enough to turn off the cold water supply and pour out the remaining liquid from the tank.

Drainage through a safety valve

The water heater connection diagram necessarily provides for installation of a unidirectional safety valve or even a pressure valve on the cold water supply pipe. The valve has several functions. So, it is necessary to prevent hot water from the boiler to the cold water supply. And otherwise, without a valve or if it will be faulty, the boiler can be empty, and the water in the toilet cistern will be hot. From a hygienic point of view, it can be useful, but it is very uneconomical, and the boiler without water will fail, its heating elements will burn out.

Another function of the valve to prevent the destruction of the boiler when heating water. As the temperature increases water increases in volume, the pressure in the storage tank increases. The valve relieves the pressure in the boiler, removing some of the water. So the heater will remain unharmed, and safe for humans, even if the water is heated to extreme values.

How to drain a water heater

drain, water, boiler

And the modern design of the valve allows you to use it to drain the water from the boiler. To do this, its design provides a lever, by pressing which you can remove water through an opening in the valve body. This way loses to draining the water from the boiler through the drain cock, as water will flow out through the valve in a thin stream, because the safety backflow preventer has other priority tasks. Therefore, you should drain water through the safety valve only if there is no drain valve.

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