Replacing the heating element in a water heater – when and how to do it

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Replacement of the heating element in a water heater – when and how to do it

A water heater is a device that most households get so used to that they hardly notice it – as long as it works. However, when it stops heating, the temperature of hot water starts fluctuating or a strange noise comes from the utility room, it suddenly becomes clear how important it actually is. The most common cause of these problems is a worn or clogged heating element – that is, the actual element that converts electrical energy into heat. The good news is that replacing this element is not rocket science and can be done by any handy DIY enthusiast. The bad news: if you do it incorrectly, you may end up with a flooded utility room or a burnt water heater. That is why we will go through the entire process in great detail – from diagnosis through selecting the correct element to the actual installation, tightness check, and restarting the system.

What is a heating element in a water heater and how does it work

The heating element (also called a heater, electric heating element, or in English a heating element) is essentially a tubular resistive heater built directly into the tank of the water heater. Electric current passes through a resistive coil inside a protective tube, which heats up and transfers heat to the water surrounding it. The whole principle is the same as in an electric kettle, only the construction is more robust and adapted for long-term operation under pressure.

The element is located at the bottom of the tank or in a side opening, where it is threaded into a connection – most commonly a 5/4" thread (i.e., an imperial thread with a size of approximately 41.9 mm). This is an important detail: before placing any order for a replacement element, you must know the exact thread of your tank. For more information on threads and flanges, see the article What thread and flange diameter do I need for a heater in a tank (5/4" and others), where less common sizes are also discussed.

The element is usually covered with a protective layer – either a galvanized coating or made of stainless steel. Each material has different properties and behaves differently in soft, hard, or aggressive water. This topic is discussed in more detail in the article Water heater heating element: brass, galvanized, or stainless steel AISI316L?

When is the replacement of a heating element really necessary

This is a question where the most common mistake is made in practice: people either replace the element too early (because they do not accurately diagnose the cause of the problem) or too late (when the element is so clogged that it also damages the regulation or the tank). Let's look at the specific symptoms that really indicate the need for replacement.

The water heater does not heat or heats very slowly

This is the most common reason why customers start looking for a replacement element. There can be several causes – thermostat, fuse, power supply failure – but if the thermostat and electrical part are in order, the problem is almost always in the heating element itself. It may be a broken resistive coil inside (a simply "burned out" element) or a thick layer of scale that prevents heat from being transferred to the water. A heavily scaled element can take 3–4 hours to heat a standard 100-liter water heater instead of the usual 90–120 minutes, while electricity continues to flow at full rate.

Tripping circuit breaker or earth leakage

If the circuit breaker for the water heater keeps tripping and the residual current device (RCCB) reports an earth leakage, it is almost always a sign of a cracked element. A crack in the protective tube allows water to reach the resistive coil, causing an earth leakage – a situation that is immediately dangerous and requires the water heater to be disconnected from the power supply and the element to be replaced. Do not attempt to reset the circuit breaker in such a case: there is a risk of electric shock.

Humming, cracking or knocking from the water heater

Noises during heating are a typical sign of limescale buildup. When the layer of calcium carbonate is thick, bubbles of steam are harder to release from the surface of the element, resulting in characteristic cracking or humming. Sometimes descaling (with citric acid or a special product) helps, but in other cases – if the layer is really thick – replacing the element is more economically advantageous than repeated cleaning. This topic is discussed in the article Maintenance of heating elements in tanks – cleaning, descaling, and anode inspection.

Visible corrosion or water leakage around the flange

If you notice rust or water droplets around the area where the element is threaded into the tank, it is a sign of corrosion of the gasket or the flange itself. In such cases, simply tightening is not enough – leakage around the metal joint must be resolved by completely replacing the element and the gasket. Otherwise, you risk the corrosion progressing into the tank thread and causing a much bigger problem.

Choosing the correct replacement heating element

Before you go to buy a replacement, you need to know several key parameters of your water heater. Without these numbers, it is easy to end up buying an element with a different power, different thread or different length – and then you will have to return to the store. Based on practical experience, we recommend always recording these values directly from the water heater's type plate or from the original element:

Power in kW (or W): In domestic water heaters, we most often encounter values of 1.2 kW; 1.5 kW; 2.0 kW; 2.5 kW; 3.0 kW. Do not confuse the power – an element with a higher power than the circuit design will strain the fuses and the thermostat switch.
Flange thread: The standard in the Central European market is 5/4" (inch), less common are 6/4" or a direct flange connection with multiple screws. These details are often engraved directly into the metal of the flange on the original element.
Element length (dip): Depends on the volume and shape of the tank. Shorter elements (335 mm or less) are suitable for small and medium tanks, longer ones (500–900 mm) for large storage tanks. It is important that the element does not reach into the suction neck area or touch the tank wall.
Surface material: Galvanized steel surface, brass flange or fully stainless steel AISI316L version. For hard water (over 300 mg/l CaCO₃), a stainless steel version is strongly recommended.
Voltage: Almost always 230 V / 50 Hz, but in industrial or commercial water heaters you may also encounter a three-phase 400 V connection.

For small and medium tanks, two proven types are available on our website. The first is Heater GRBT for small and medium tanks with a brass flange and galvanized surface (1400 W, 335 mm, 5/4" thread) – a classic solution for regular city water. If your area has harder or more aggressive water, we recommend reaching for Heater GRBTN made of stainless steel AISI316L (1400 W, 335 mm, 5/4"), which significantly better resists the corrosive effects of mineral-rich water and has a much longer lifespan.

What you will need – tools and materials

Proper preparation is half the success. From practice, I know that the most common mistake is when a DIY enthusiast starts disassembling and then realizes they do not have the right wrench or are missing a gasket. List of required tools and materials:

Adjustable wrench or a special flange wrench for 5/4" (approx. 55 mm diameter) – classic combination wrenches are not sufficient here, you need either a large pipe wrench or a special head
Plumber's wrench or water pump (pigeon) – an alternative in cases where a special wrench is not available
Large container (bucket, 10–15 liters) or a drain hose to drain the water heater
Teflon tape (PTFE) and/or a new rubber gasket – never reuse the old gasket
Silicone sealant for plumbing work (optional, but recommended for old threads)
Electrical tape and screwdriver
Multimeter (to verify that the circuit is truly de-energized)
Work gloves and a cloth

Step-by-step replacement of the heating element

The following procedure is verified in practice and reflects the most common construction variations of domestic pressure water heaters with side or bottom flange. For non-traditional types (e.g., water heater with two elements or a combined flow system), consult the manufacturer's technical documentation.

Step 1 – Disconnect from the electrical network

Never start working on a water heater without first switching off the circuit breaker for the water heater circuit in the distribution board. It is not enough to just turn off the thermostat – you need to have the circuit physically disconnected. After turning off the circuit breaker, check with a multimeter at the water heater terminals (you will reach them after removing the cover of the terminal box) that the voltage is indeed zero. It may sound pedantic, but this is the number one safety step, without which I would not proceed to the next steps at all. In older installations, it can happen that the circuit breaker is not properly labeled and the water heater is connected to a different circuit.

Step 2 – Closing the water supply and draining the tank

Close the main cold water shut-off valve to the water heater – either the central house valve or a local ball valve (if installed near the heater). Then open a hot water tap in the bathroom or kitchen to relieve pressure in the system and allow water to drain. At the bottom of the heater, you will find a drain valve (or the flange itself may serve as the valve) – attach a hose and drain the contents into a bucket or drain. Draining a 100-liter heater takes 10–15 minutes, and it will naturally take longer for a larger unit. Sometimes it is enough to drain only part of the water so that the level is below the flange – this depends on the position of the heater body installation.

Step 3 – Disconnecting electrical wires and removing the terminal cover

Unscrew the plastic cover of the terminal block and take a photo of the current wiring (colors, positions) – you will need this for reassembly. Unscrew the wires from the terminals. Most domestic water heaters have a three-wire connection (L, N, PE – i.e., live, neutral, and protective conductor). Some older models have only a two-wire connection without a grounding conductor – if you encounter such a model, it is a good opportunity to add grounding according to current electrical standards during replacement.

Step 4 – Unscrewing the old element

This is the technically most demanding step. The 5/4" thread requires a relatively high torque, and since the element may have been in the tank for years, the thread may be stuck due to scale or corrosion. Use the correct wrench – ideally a special flange wrench for 5/4", which fits the entire hexagonal flange. When applying significant force, use an extension tube on the wrench (so-called pipe), but be careful with the direction – always turn to the left (standard thread). Before unscrewing, place an old towel underneath – even though the heater is drained, some water (a few liters) will spill out when the thread is released.

If the thread is corroded and the element does not move, try applying penetrating oil (WD-40 or similar) to the joint and wait 15–30 minutes. In extreme cases, gentle heating of the area around the flange with a gas torch (note: only the steel shell of the heater, not the welded seams!) may help expand the material. Never use excessive force without adequate support for the heater – you risk damaging the tank or the thread.

Step 5 – Checking the condition of the thread and preparing for the new element

After removing the old element, inspect the thread in the tank. Use a brass brush or fine wire brush to remove scale and corrosive deposits from the thread. If the thread is damaged or cut, the situation is more complicated and may require special thread inserts or even replacement of the entire tank (which in practice is a signal to replace the heater). Also check the condition of the anode – if it is within reach of the flange opening and is significantly corroded (reduced to a thin core), it is a good opportunity to replace it. More on this in the article Maintenance of tank water heaters – cleaning, descaling, and anode inspection.

Step 6 – Installing the new heating element

Wrap 3–5 layers of PTFE tape (Teflon tape) on the thread of the new element in the direction of the thread (when viewed from the front, wind the tape clockwise). Some elements are supplied with a rubber gasket – in such cases, use a combination of gasket and PTFE tape, or follow the manufacturer's instructions for the element. Start screwing by hand – you must feel that the thread engages properly and does not damage the new thread. When the element is tightened by hand as far as it will go, finish tightening with a wrench using moderate force (you don't have a torque wrench, but a firm tightening without cracking the gasket is sufficient). Do not over-tighten – the brass or stainless steel flange is strong, but the thread in the steel tank has its limits.

Step 7 – Filling and leak test

Before connecting the electrical part, always first fill the heater with water and check the tightness of the mechanical connection. Open the water supply and wait until the tank is filled (you will notice this when a steady stream of water starts flowing from the open hot tap in the bathroom), then close the tap. Leave the system under pressure for about 10–15 minutes and visually inspect the area around the flange. If there is no drop, the connection is tight. If it leaks – which often happens with old threads – you must drain, slightly tighten the element, or add a layer of sanitary silicone to the outer edge of the flange and repeat the process.

Step 8 – Connecting the electrical part and verifying operation

According to the photo from the disassembly, reconnect the wires to the terminal block (L – live, N – neutral, PE – green-yellow grounding conductor). Close the terminal block cover, turn on the circuit breaker in the distribution board, and set the heater thermostat to the desired temperature (usually 55–65 °C for normal operation). Wait a few minutes and observe whether the indicator LED (if your model has one) lights up, indicating that the element is drawing current. After full heating (1.5–2 hours for a 100-liter tank), check the temperature of the hot water at the tap. If everything works as expected, the replacement is successful.

Common mistakes when replacing a heating element

Over the years of practice, I have seen several recurring mistakes that unnecessarily complicate the work or lead to repeated failure:

Incorrect element power: People buy a higher power element "so it heats faster" – and then wonder why the circuit breaker trips or why the thermostat fails after a few months. The power must match the design specifications of the heater.
Forgetting to drain the tank: Surprisingly, this happens. The result is a flooded utility room and a wet technician.
Using an old gasket: An old rubber gasket after many years loses its elasticity and does not seal properly during reinstallation. Always use a new one.
Turning on the heater without water: If you turn on the heater before the tank is filled, the element will burn out in a few minutes (dry operation). No electric water heater should be turned on without water.
Ignoring the condition of the anode: While you are already open, check the anode. Replacing it at the same time significantly extends the life of the newly installed element and the tank.
Incorrect element material for water type: In areas with hard or aggressive water, installing a galvanized element instead of a stainless steel one means you will have to repeat the entire process in 2–3 years.

Differences between water heaters – what affects the replacement process

Not all water heaters are the same, and the replacement process varies depending on the construction. Pressurized storage water heaters (the most common type in apartments and houses) have a body accessible from the side or from the bottom via a hexagonal flange nut. There are, however, also variations:

Dual-element water heaters: Have one main body at the bottom and a second one at the top (for fast heating of a small volume). In case of a failure, you need to identify which one is non-functional.
Combined water heaters (solar + electric): Have a coiled heat exchanger for the solar circuit and an electric element as a backup. The element replacement is identical in this case, but you need to be careful not to damage the heat exchanger when using a wrench.
Pressurized mini-water heaters (5–15 liters): Are usually accessible from the bottom, the element is shorter and sometimes has a less common thread. Always verify the parameters with the manufacturer or on the data plate before replacement.
Non-pressurized water heaters (open): The element is accessible from the top, but these types are very rare today – you are more likely to find them in old cottages or industrial facilities.

Heating element vs. heating rod – what is the difference

Sometimes customers ask us whether a heating rod is the same as a heating element. The answer is: similar principle, but different application. A heating element (for tank installation) is constructed for built-in use in a sealed pressurized tank and operates under the pressure of the water supply system (usually 3–6 bar). A heating rod is a device for radiator or bathroom panels – you insert it into the panel’s opening (usually 1/2" or 3/4" thread) and it heats the panel electrically, without connection to the central heating system.

If you are looking for a solution for a bathroom panel, take a look at Heating rod with thermostat for radiator panel (300 W, white) – it is specifically designed for this purpose and you should definitely not put it into a water heater, just as you would not put a pressurized 5/4" element into a panel. More on this topic can be found in the article Installation of a heating rod into a radiator panel – step by step.

Economics of replacement – is it worth replacing the element or the whole water heater?

This is a practical question customers often ask, and it has a clear answer: it depends on the age and condition of the tank. A rule of thumb from practice says that if the water heater is younger than 8–10 years and the tank is not corroded and the pressure relief valve is still functioning, replacing just the element is economically advantageous. The price of a new heating element ranges in the tens of euros, while a new water heater costs from 80 to several hundred euros plus installation and disposal of the old one. If the water heater is older than 12–15 years, the anode has not been replaced for years and the tank is starting to corrode, a full replacement makes more sense – you avoid the situation where you replace the element in a year and deal with a leaking tank in two years.

Concrete example: a customer with a 10-year-old 150-liter Dražice water heater, the element burned out due to overpressure (he forgot to open the air vent before turning it on). The anode was still solid, the tank was free of corrosion. Replacement of the GRBT 1400W element with a brass flange for the cost of materials and one hour of labor – the water heater has been working smoothly ever since.

On the other hand: a customer with a 16-year-old unbranded water heater, cracked enamel inside the tank, anode not replaced for years. A new element would be only a temporary fix – we recommended replacing the whole unit.

Replacement frequency and preventive maintenance

A standard heating element should last 8–12 years with proper maintenance. The main factors that shorten its lifespan are:

Water hardness – the harder the water, the faster limescale builds up
Operating temperature – an element set permanently to 75 °C degrades faster than at 55 °C
Condition of the magnesium anode – the anode "sacrifices itself" to protect the tank and the element; when it is depleted, the element starts to corrode
Material of the element – AISI316L stainless steel elements handle aggressive water significantly better than galvanized ones

Preventive inspection every 2 years (including visual inspection of the element when opening the service hatch and replacing the anode) can extend the life of the whole water heater by years and save money on emergency interventions.

FAQ – Frequently asked questions about heating element replacement

Can I replace the heating element myself, without an electrician?

Demounting and mounting the element itself is a standard plumbing task and does not require an electrician’s license. The electrical part – connecting the wires to the terminal block – is reserved for electricians in most cases, unless you are not changing the original wiring and are not making any changes to the distribution board. In a simple replacement (same type of element, same wiring) and if you are capable of safely working with voltage terminals after checking them with a multimeter, a skilled DIY enthusiast can manage it. If you are unsure, better call an electrician – element replacement is cheap, but the damage from incorrect wiring can be expensive.

What power rating should I choose for the replacement element?

Always the same as the original one in the water heater. The power rating is indicated on the data plate of the water heater or on the old element itself (engraved digits on the flange). If you cannot determine the original power rating, contact the water heater manufacturer with the model number – they will advise you. More on choosing the right power rating can be found in the article What power rating do I need for a heating rod – 150, 300 or 600 W?

How long does it take to replace a heating element?

An experienced technician can do it in 30–60 minutes including draining and refilling. A DIY enthusiast doing it for the first time, who has to find the right wrench, deal with a stubborn thread and let the gasket dry, should expect 2–3 hours. The longest part is draining and refilling the tank – the element replacement itself takes 10–15 minutes.

What to do if the water heater still does not heat after replacement?

Check in this order: 1) Whether the new fuse (circuit breaker) is intact and has not tripped; 2) Whether the thermostat is set to a sufficient temperature and is functioning (thermostats also have a limited lifespan); 3) Whether the water heater is actually full of water and there is no air pocket in it; 4) Whether the new element has the correct voltage and is not "dry" (switched on without water). More on diagnostics can be found in the article Common faults of heating rods and heaters – why they do not heat or trip the circuit breaker.

Do I need to replace the gasket when replacing the element?

Always yes. The old rubber gasket loses its elasticity over the years and does not seal reliably after remounting. Most new elements are delivered with a new gasket – if not, buy a separate rubber gasket with the appropriate diameter (for a 5/4" thread, it is a gasket with an outer diameter of about 60 mm and an inner diameter of about 42 mm). The cost of the gasket is negligible compared to the cost of water on the floor.

Can I install a stainless steel element into a water heater that originally had a galvanized one?

Yes, and in many cases it is even recommended. A stainless steel element made of AISI316L steel is material-compatible with standard steel tanks and brass anodes and provides higher resistance to corrosion. The only thing to keep in mind is that the thread and power rating must remain the same. Replacing with a stainless steel type is especially suitable in areas with hard or aggressive water, where galvanized elements last only 3–5 years.

Conclusion – element replacement as prevention, not just rescue

Replacing a heating element in a water heater is not a dramatic intervention – it is a routine, well-manageable service operation that, when done correctly and with the right replacement part, pays off significantly better than ignoring the problem or hastily replacing the whole appliance. The key is to recognize the signs of failure in time, choose an element with the correct power, thread and material according to water quality, and proceed safely – always disconnected from the power supply, always checking the seal before turning it on.

If you are facing a specific decision about replacement, further practical topics in our Knowledge Center can help you – for example Water heater element: brass, galvanized or stainless steel AISI316L? or Common questions about heating rods and tank heaters. And if you need a specific product, take a look at our range – for example GRBT heater with brass flange and galvanized surface for standard conditions, or the more durable GRBTN heater made of stainless steel AISI316L for more demanding environments – both in a proven version for small and medium tanks with a 5/4" thread.

Do you have a question about this topic?

Not sure what to choose or dealing with a specific situation in your home? Write to us – we are happy to help.