Why the water does not flow or badly flows from the boiler and how to fix the problems

Water heaters are commonly installed in residential and commercial buildings to provide a steady supply of warm water when the main hot water supply is not available or the boiler room is temporarily shut down. Even though high-quality appliances and proper installation can help prevent malfunctions, there is no guarantee that breakdowns will not occur. Many consumers encounter issues where hot water fails to flow from the boiler or the water pressure is insufficient, prompting them to contact repair specialists for assistance.

Diagram of a water heater storage system

Hot water does not flow from the boiler: why and how to fix it

The primary function of a storage water heater is to achieve and maintain a specific water temperature. However, over time, issues can arise, such as weak water pressure or the delivery of cold water instead of warm water. These problems typically occur due to inadequate equipment maintenance, including:

• Accumulation of limescale on the heating element
• Malfunction of the pressure regulator
• Thermostat failure
• Mixer contamination
• Incorrect heating settings

Prior to activating the equipment, it is essential to first turn off the hot water supply on the pipe and open the faucet tap. Failing to do so will result in the tank not being able to fill up and air not being released. Additionally, hot water from the pipe will be redirected to neighboring units, leaving the boiler with cold water or no water flow at all.

In order to identify the cause of the malfunction, start by tightening the mixer valve, disconnecting the device from the power source, emptying the tank, and proceeding with the inspection. It might be possible to resolve the issue independently.

Limescale

When hard water and high temperatures are present, salt can quickly build up on the walls of the boiler and heating coil. This buildup, known as limescale, can make it difficult to heat water and eventually cause the heating coil to burn out. If an inspection reveals that the electric heater is covered in deposits, the following steps should be taken:

• Remove the protective cover.
• Unscrew the bolts holding the heating element in place.
• Remove the heating element and clean it by soaking it in a solution of citric acid.
• Place the coil back in its original position.
• Use a tester to check the contacts.

If, after cleaning, the heating element is still operational, the construction can be reassembled in reverse order. However, if the coil is no longer functional, it will be necessary to replace the burned electric heating element.

Pressure reducer

Within the water supply system, pressure fluctuations ranging from 2.5 to 7 atmospheres occur. In order to safeguard the boiler from deformations resulting from such fluctuations, a specialized regulator is implemented at the entry point. Once this particular unit has been precisely adjusted, water will flow from both the storage tank and the tap with equal force. It is imperative that the pressure at both the tank inlet and outlet be equivalent. Should the water pressure from the appliance prove to be inadequate, it is necessary to either adjust or replace the pressure reducer.

Insufficient water supply from the boiler may also stem from low pressure within the cold water pipes. To determine this, simply turn the cold water supply valve. Should the flow be meager or nonexistent, repairs are likely underway.

Thermostat

If the heating element is not turned on, water heating will not occur. To identify a faulty component, the following steps can be taken:

• Disconnect the contacts and remove the thermostat from the housing.
• Press the fuse button.
• Apply heat to the copper tip (if the button turns off, it indicates a faulty element).
• Use a multimeter to measure the resistance at the contacts.

It is possible that the overheat protection has tripped and the unit’s functionality has been restored. If the tester is not producing any sound, it indicates a failed thermostat that needs to be replaced.

Faucet

If the water is coming out of the boiler in a weak stream, it could be a sign that the faucet is clogged. To fix the issue, you will need to remove the spout from the mixer, clean the filter mesh to remove any debris, scrub the internal circuit with a brush, and then reassemble the components. Another possible cause for low pressure is a faulty valve on the hot water faucet. If the components are severely worn, it may be best to purchase a new mixer.

To prevent frequent replacement of parts, you can install a system of filters at the inlet to the boiler.

Why the water heater does not fill

Filling the boiler may seem like a simple task, but it is important to follow the correct steps:

1. Start by opening the hot water drain cock on the faucet that is connected to the boiler, followed by the cold valve of the common water supply.
2. As you do this, the liquid will gradually fill the tank and expel any air with a hissing sound.
3. You will notice that the water level in the tank starts to rise and eventually overflows into the spigot (level B in the illustration).
4. Once you have a steady stream of water flowing, you can then shut off the mixer.

A diagram illustrating the flow of water in the boiler

When filling the water heater, it is important to ensure that it is properly plugged in. This is the ideal scenario. However, sometimes the boiler may fail to draw cold water, despite the water supply being functioning properly. What factors can impact the performance of the heat exchanger causing this behavior?

Clogged filter

When the water enters the boiler, it undergoes a filtration process to remove impurities. To accomplish this, the appliance is equipped with a mesh filter that traps debris and rust particles. If the metal grid gasket becomes dirty, a plug made of debris prevents the water from flowing freely. To restore normal filling of the boiler, you must remove the plug from the bulb and take out the grid. Clean it in the same manner as the faucet filter and reinstall it.

There are also replaceable filters with gel filling. If the material used is of low quality, it can leak out and obstruct the water passages. If this is the case for you, the solution is simple: purchase a proper filter. However, you will need to make an effort to thoroughly clean the water intake tubes with a hairbrush.

Incorrect assembly

It is possible that the cold water intake hose and the heated water outlet are mistakenly connected, and vice versa. This situation can occur, particularly if the installation was carried out by an inexperienced person. As a result, the boiler may malfunction and water will not be able to enter it. The same issue can occur if the safety valve is wrongly connected. The solution to this problem can be provided by a professional.

Defective check valve

To ensure that the water remains inside the boiler and does not flow back into the main water supply, the device incorporates a safety valve. The safety valve is strategically positioned after the shut-off valve, just a short distance from the tank, and functions in a unidirectional manner when water is being drawn in. Additionally, the safety valve is designed to relieve any excess pressure that may build up. In instances where the water temperature is extremely high, the valve’s locking mechanism disengages the spring, allowing the excess liquid to be discharged and the pressure to be stabilized.

If the valve becomes worn or if there are any large particles that enter the valve mechanism, it can become jammed and prevent water from entering the boiler. One common occurrence is that scale can build up and block the chamber behind the disc spring. To restore the proper functionality of the unit, it is necessary to remove the valve, take it apart into its individual components, and thoroughly clean it. If the attempt to clean it is unsuccessful, it is important to not leave the equipment without a valve.

Experts suggest the installation of a safety check valve on the water heater to prevent the occurrence of dangerous outcomes, such as an explosion, caused by overheating.

Rapidly running out of water in the boiler

Using a large amount of water during the summer and having a slight heating requirement may result in the boiler running out of water more quickly. It is also possible that the tank is experiencing too much pressure, causing the safety valve to release excess hot water. Alternatively, if there is low pressure in the main water pipe, cold water may not be effectively pushed into the boiler, causing it to be only partially filled.

Furthermore, it is possible that the heating element has been recently replaced with a less powerful one. While the temperature regulator remains in the same position, the new heating element is not able to adequately heat the water. There are numerous factors that can contribute to a water heater losing water quickly, and a few of them are discussed below.

Leak in the casing

Boilers are constructed using strong materials that have the ability to withstand high levels of pressure and weight. However, over time, if proper maintenance is not performed, corrosion may begin to develop on the interior of the tank, resulting in small openings through which water can escape. The occurrence of corrosion is influenced by several factors:

• Accumulation of salt deposits on the inner walls;
• Buildup of limescale;
• Extended periods of inactivity without proper drying.

If a boiler becomes corroded, it is important not to attempt to repair it by welding the holes. A corroded housing is not functional and should be appropriately disposed of in a designated landfill.

The corrosion of the boiler drum has resulted in a buildup of rust.

Leaky connections

It is essential to ensure a secure and gap-free connection of check valves, reducers, and other components in the sanitary construction. To achieve this, it is recommended to use hemp, fumed tape, or plumbing thread for sealing the joints, and then fill them with sealant. Neglecting this step would result in potential leakage from the boiler, which can eventually lead to failure. In addition, if the thermal protection mechanism fails, it can cause the heater to burn out.

Weakness of the safety check valve

It is considered normal for water to leak through the valve outlet if a liter jar of water drips out of the valve within a day. This excess water is produced due to the pressure buildup from heating. However, at times it is difficult to gauge the amount of liquid flowing out as it drains through the hose into the sewer. If the boiler empties exceptionally fast, it may indicate a faulty valve. In such cases, it is advisable to replace the valve with a new one, and it is generally recommended to do so on an annual basis.

Dripping water from the valve is a common occurrence and does not indicate any major issues.

However, it is essential to note that draining the boiler through the safety valve opening is strictly prohibited. The accumulation of scale and sediment can block the drainage pores, impairing the mechanism’s functionality.

Tips for boiler maintenance

1. Even with excellent thermal insulation, it is impossible to avoid heat loss when using a heater. Therefore, it is advisable not to set the temperature regulator to the maximum level. If water consumption is moderate, it is better to heat the water to a medium temperature to avoid dilution. It is recommended to set the heater to a high temperature when you need to take a shower and expect to use a large amount of water. Lowering the temperature will also help reduce scale buildup.
2. If you plan on being away from home for a few days, it is recommended to turn off the water heater, but leave it filled with water. However, it is important to note that turning off the heater at night will not save energy and can potentially lead to increased wear and breakdowns of the electronics components, which may experience frequent overloads.
3. After a long period of inactivity, it is necessary to drain the stale water, rinse and refill the boiler. To eliminate any odor and bacteria, the boiler should be heated at maximum temperature for two hours. If the boiler will not be used for an extended period of time, such as during winter in a rural area, it should be emptied, thoroughly dried, and stored in a warm location.
4. To help prevent the buildup of limescale on the boiler walls, a useful component like a magnesium anode can be utilized. Over time, the anode will dissolve and should be replaced approximately once a year. However, it is important to consider whether interfering with the equipment’s operation is necessary in each specific case. Water hardness and impurities vary, but if the unit begins to make crackling sounds and heat up more slowly, it may be beneficial to disassemble the design and inspect the interior.

Water Heater Anode

1. One way to make water softer is by using a filter at the boiler’s inlet. The filter cartridge is filled with a special resin that displaces magnesium and calcium ions and replaces them with sodium ions. Another method to reduce water hardness is by installing a hydromagnetic system. The magnet crystallizes the salts, transforming them into sludge that can be captured by the filter.

An adequately installed and efficiently operated water heater can last for up to 15 years. Its longevity depends on various factors, including water quality and the quality of its parts and components. When it comes to diagnostics and repair, it is important to follow the instructions provided rather than relying on random methods.