How to choose a water heater
Types and purpose of water heaters
There are several types of water heaters depending on the source of heating and the principle of operation, which is the most important parameter at the very beginning of the choice. There are electric, gas, indirect and combined models of different volume and power on the market. Each type of water heater has its own purpose, so it will be better to cope with its tasks in certain conditions.
Gas water heater. The flowing gas water heater is an efficient option when connected to a central gas supply and installed in compliance with technical standards. It is suitable for both apartments and private houses, providing sufficient hot water for a large family. With a capacity of 10 — 15 liters per minute, it can easily handle showers and hot baths. Despite its flow-based operation, this type of water heater maintains a stable water temperature even with minor pressure fluctuations. Multiple water intake points can be connected, but simultaneous usage may cause a noticeable drop in water temperature. To avoid this, it's essential to select a model with adequate power to meet your needs.
Modern gas water heaters come equipped with essential safety systems. Gas control prevents gas leakage when the flame goes out, while overheating protection cuts off the gas supply if the heat exchanger temperature exceeds safe levels. Advanced models may include a draft sensor to prevent combustion product ingress, and protection against turning on without water to safeguard the heat exchanger during a "dry" start. These security features are crucial to avoid potential hazards, so it's essential not to compromise on quality when selecting a gas heater. The main drawback of these heaters is their complex installation process and the requirement to obtain permits from local gas services.
Gas storage water heater. A gas storage water heater is a large tank (100+ liters) that heats water through a gas heat exchanger. It offers good efficiency, but its installation, operation, and maintenance are challenging and require documentation and adherence to gas service regulations. The installation must follow specific standards, and the heater's bulky size demands ample free space. Due to its high cost, this type is not commonly used. Repairing the storage tank is nearly impossible if damaged. However, in situations without electricity and when there is a constant need for large volumes of hot water, a gas storage water heater might be the only suitable option.
Indirect water heater. An indirect water heater is a passive system that relies on the home heating system for its operation, without having its own electric or gas heating source. It works by heating water in the tank through the heat exchanger, using liquid that has already been heated by a water heater or other equipment. The main advantage is the absence of costs for obtaining hot water. However, its heating efficiency is lower compared to gas and electric heaters due to the limited temperature of the heating system. Another drawback is its seasonality of use, as it relies on the home heating system, which is usually turned off in the warmer months. Therefore, indirect water heaters are best used as additional units to save money during the heating season.
Combined water heater. The water heater combined the benefits of indirect and electric storage types. It offers continuous hot water supply throughout the year and allows for savings during the heating boiler operation season. The built-in heating element can work together with the indirect heat exchanger or independently, providing hot water at any time. Some models have multiple heating elements to expedite the process of obtaining hot water, especially in large tank volumes (over 200 L). This type of water heater is ideal for those with an individual heating system or those planning to install one soon. It is well-suited for private homes, workplaces, and large families.
Tankless electric water heater. A tankless electric water heater is a standalone unit that connects to the central water supply system and can be used as the main or additional source of hot water. It uses a coil or heating element for heating. This type is suitable for meeting various hot water needs, such as in the kitchen, for taking showers, or providing hot water in areas without a gas supply like summer cottages. It can achieve a flow rate of 8 — 10 liters per minute at 25°C, with a maximum temperature of 80°C. Tankless electric water heaters are ideal for occasional use, ensuring that water does not stagnate in containers. They can serve only one point of use and require robust electrical wiring to handle high loads, given the heating element's power, which usually exceeds 5 kW and can reach up to 20 kW.
Instant water heater tap. A compact monoblock device that replaces a standard mixer, the instant water heater is space-saving but has lower performance. It comes with a powerful heating element (3 — 4 kW), which may be problematic for older house wiring. It can provide an average of 2.5 liters of water per minute at 25°C. This type is suitable for places with low and irregular water consumption, such as kitchen sinks in apartments or private houses, and restrooms in cafes and restaurants. It may not be suitable for connecting a shower or filling a bathtub, but it prevents water stagnation and bacteria growth. The maximum temperature it can reach is 60°C, which is sufficient for everyday household tasks.
Storage water heater. The electric storage water heater is a popular and highly demanded type of water heater, known for its numerous advantages. It finds extensive use in residential, commercial, and industrial settings. Unlike tankless heaters, it has a storage tank where the heating element is located, allowing for a continuous supply of hot water ranging from 10 to 1000 liters, which can be efficiently replenished in short periods (1 — 4 hours). These water heaters demonstrate excellent efficiency, making them suitable for both small apartments and large families with high year-round hot water needs. Manufacturers constantly improve their internal design, using corrosion-resistant materials and incorporating automation, RCDs and smart programmers to enhance their functionality. Electric storage water heaters are considered the most optimal option in terms of the price-to-quality ratio and efficiency. The wide variety of models available can make the decision-making process challenging. Therefore, important criteria for selecting an electric water heater will be discussed to help individuals choose the right model that meets their specific needs.
Consider the following factors when selecting a water heater
To choose the right electric storage water heater, you need to act consistently. There are many different criteria to consider. Some are mandatory, others are optional.
Installation method
The first step in choosing a water heater is to determine its location, considering future operating rules. Ideal installation sites are places with low humidity, such as the kitchen or toilet. Next, you need to decide on the installation method, which includes options like suspended, floor standing, vertical or horizontal or a a universal type that allows the tank to be rotated 90° before installation, providing different connection options.
Housing shape
The second criterion that will allow you to avoid problems associated with installation is the shape of the case. Storage water heaters, especially those with large volumes, can be quite bulky. Therefore, it's crucial to choose a suitable shape that doesn't require making additional holes in walls or breaking partitions. Manufacturers offer classic cylindrical tanks, which are more affordable but take up more space. Alternatively, rectangular models have a reduces depth, but are still large in size. These options are suitable for spacious rooms where saving free space is not a concern.
For limited space, flat and narrow water heaters are provided. The former are oriented to the minimum depth, but take up more space in width. The latter are distinguished by their minimum width and depth, but are quite high.
Volume
The volume of the storage tank is a personal consideration that requires advance planning. If you enjoy hot baths or take longer showers (over 15 minutes), it's advisable to choose a water heater with 80 liters or more. This option is also suitable for families of 2 — 3 people who primarily use showers. For smaller consumption needs, such as washing dishes, a tank volume of 50 liters or less is sufficient. On average, one person needs about 30 liters of water.
To ensure sufficient hot water availability and prevent the tank from fully cooling down, it is recommended to choose a storage tank with a capacity 15 — 20% higher than the expected consumption. Ready-made tables that correlate volume with consumption exist, but they are only advisory, as individual water usage varies for each person.
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Heater type
The choice of heater type is a crucial factor that affects heating efficiency, safety, and durability of the water heater. Manufacturers offer two options — dry or wet heating elements. Wet heating elements are commonly used, cost-effective, and can operate without issues if the water meets quality standards. However, hard water with impurities can lead to scale formation on the heating element, reducing efficiency and increasing electricity consumption and heating time. On the other hand, a dry heater is more reliable and durable but comes at a higher cost. It remains protected from contact with water by an additional shell made of metal or ceramics, containing oil, quartz sand, or air. The efficiency of a dry heating element remains consistent over time, as scale formation on the outer shell is minimal. The choice between the two types depends on the user's low-cost and preferences.
Interior tank coating
Hard water, temperature changes, high pressure in pipes can destroy walls made of metal, so manufacturers cover them with an additional inner layer made of various materials. The durability of the tank itself, its ability to resist mechanical and thermal effects, corrosion depends on the quality of the internal coating. This is a fairly important factor, on which there is no point in saving. Even the most advanced water heater can leak if the inner coating is of poor quality.
The most common is enamel, which is affordable but limited in features. An enamel coating on the tank's interior surface prevents the formation of scale due to its smooth texture. However, temperature fluctuations can cause microcracks, leading to tank wall corrosion and eventual leaks. For situations with moderate water flow and the ability to set the thermostat temperature to no higher than 60°C, a water heater with an enamel coating is suitable. However, in winter months, this approach may be less effective as the low temperature of incoming water can quickly reduce the temperature inside the tank.
Some manufacturers use titanium enamel, which is not susceptible to high temperatures, but is more expensive. Such a coating successfully copes with its tasks and is suitable for any operating conditions.
Glass ceramic is a relatively new coating, widely used since 2010, that can effectively protect the tank from corrosion as long as the water temperature stays below 60°C. If the temperature exceeds this limit, cracks may develop, similar to ordinary enamel coatings. The advantage of glass ceramics is its neutrality towards the liquid, as it does not react with water, maintains its physical and chemical properties, and inhibits the growth of bacteria and odors. This coating is suitable for showering and washing dishes. During warm months, it may allow for bathing, but in winter, it can be problematic due to the very low temperature of the water in the pipes entering the tank.
Stainless steel is considered the most practical and reliable coating. It is not afraid of changes in temperature and pressure. When choosing stainless steel, you should give preference to more expensive water heaters with high-quality processed seams. Otherwise, you can detect a leak after a few years of operation.
Safety
Depending on the operating conditions, external factors and features of the premises, it is possible to identify the main protective mechanisms that will save users from unpleasant breakdowns.
Overheating protection. It does not allow exceeding temperature limits and prevents damage to the heating element. Indications are read by a special sensor. Installed by default in most water heaters.
Frost protection. The system relies on sensor readings, detecting a decrease in temperature to a critical level, and automatically activates the heating process. This safeguard prevents water freezing and potential deformation of the container or pipes. This protection is especially relevant when installing the tank in unheated premises, such as warehouses, basements, cottages, or summer kitchens.
Dry heating protection. Avoids "dry" activation, which can lead to failure of the heating element. The protective mechanism will help in case of water supply failures that can occur both in an apartment and in a private house.
Voltage surge protection. The voltage surge protection system typically employs a protective shutdown mechanism triggered when the voltage in the network exceeds the upper or lower permissible limits. The upper limit is usually set at 240 V, while the lower limit is at 190 V. This feature is essential to consider, particularly in regions with unstable voltage, especially in rural areas.
Electrical protection (RCD). The Residual Current Device (RCD) helps prevent electric shocks in the event of heating element shell damage or a short circuit. Although this protection is not commonly installed in water heaters due to the low likelihood of such dangerous situations, most electrical networks already have circuit breakers between the meter and the consumer, which turn off the electricity supply during a short circuit. However, if you have doubts about the effectiveness of circuit breakers or they are absent in your electrical network, it is essential to have an RCD in the water heater as an added safety measure.
Anti-legionella. Irrespective of the water quality entering the tank, there is a possibility of pathogenic bacteria multiplying and unpleasant odors developing. This risk becomes higher when using low-temperature water or during water stagnation, such as during vacations or business trips. The "Antilegionella" mode is essential in disinfecting the tank's internal contents with high temperatures (ranging from 65 to 80 °C) when needed, safeguarding users from the harmful effects of parasites.
Magnesium anode. To combat corrosion, the water heater requires an element that neutralizes chemical, electrochemical, and physicochemical adverse effects on its inner metal walls, thereby extending its lifespan. In most cases, this protective element, typically a magnesium anode, comes standard with the water heater. However, it is essential for users to be aware that the magnesium anode degrades over time and needs to be replaced periodically.
Pressure reducer. A separate device, not included with the water heater, can protect it from leaks. This device is called a reducer and its main purpose is to regulate the incoming water pressure, preventing water hammer and avoiding potential damage not only to the water heater but also to other appliances like dishwashers, washing machines, and water purification systems. Reducers are often necessary in buildings with high water pressure, such as the first floors of skyscrapers. However, pressure surges in the water supply are common in various countries and cities, making it advisable for everyone to consider purchasing this low-cost-friendly and simple device.
Pressure relief valve. The pressure relief valve is a mandatory device for installing a water heater and a requirement for warranty service in case of breakdowns. It is installed right before the inlet to automatically release excess pressure that may build up inside the tank. This valve plays a crucial role in protecting the inner coating from physical deformations and potential leaks. While it is usually included in the package, it is essential to regularly check its condition and promptly replace it if needed.
Control type
Water heaters can be controlled by electronic or mechanical systems, and the choice depends on the user's needs and low-cost. Mechanical control is considered simpler, more reliable, and cost-effective. It uses switches and regulators that are less prone to wear and damage from power surges. However, it offers limited functions and less precise control over operation parameters. On the other hand, electronic control is more expensive, but more convenient. It allows for fine-tuning the temperature, creating custom operation schedules, using economy modes, and even remote control via smartphones. Electronics, however, require additional protection like voltage stabilizers to prevent control board failures. If water consumption is constant and basic features are sufficient, mechanical control is a good option. But if consumption varies based on time or days of the week and advanced features are desired, electronic control with built-in programmers and smart functions is recommended.
Guarantee period
The manufacturer's willingness to provide a long-term guarantee is indicative of a well-made product, but the warranty period also depends on the price category of the water heater. Premium boilers with good coverage and smart features typically come with a 7-year tank warranty. In the middle price category, a reliable water heater is guaranteed for 4 to 6 years. Low-cost models may have lower quality and are usually offered with a 3-year warranty. It is essential to consider the internal tank's quality, as poor construction may lead to the need for early replacement of the entire water heater, as repairs are often impossible or more expensive.
Recommendations for the maintenance and operation of the water heater
To protect the water heater from unforeseen breakdowns and increase operating efficiency, it is necessary to adhere to certain recommendations:
- Install the water heater in rooms with normal humidity levels to avoid damage to electrical components
- When installing the water heater, use a reducer and a stabilizer to normalize the water pressure and electrical voltage
- Do not activate the heating when the tank is empty to protect the heating element from burning
- In the case of an enameled and glass-ceramic inner coating of the tank, try not to allow prolonged heating above 60 — 65 °C. Operation at high temperatures will lead to the destruction of the protective layer
- Depending on the quality of the water entering the tank, it is necessary to change the magnesium anode every 2 — 3 years
- If the water heater does not have an anti-legionella mode, periodically set the maximum heating temperature to avoid the development of bacteria, parasites and musty smells
- Periodically check the integrity of the pressure relief valve and change it if necessary to eliminate increased pressure inside the tank
- Install filters directly into the central water supply to keep the water heater and other equipment from clogging. Otherwise, it will be necessary to clean from scale, mule, sand and other compounds that get inside with water
In conclusion, an electric storage water heater is available in various volumes to meet different needs and accommodate varying numbers of inhabitants. A recommended guideline is to have 30 liters per person. For country settings or unheated rooms, water heaters with frost protection should be considered. To have a water heater that fits your schedule and preferences, look for models with programmers and smart modes. It's important to remember that low-cost options may not be of high quality. Choose a device with a durable internal coating and maintain it properly by timely replacing the magnesium anode, pressure relief valve and installing a reducer and filter to prolong its performance.
If you still have questions regarding the installation, operation and maintenance of the water heater, then you can get detailed answers in this article.
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