Installation of a hot water storage tank – procedure, connection and commissioning

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Installation of a hot water storage tank – complete procedure from delivery to commissioning

A hot water storage tank is the heart of any system where the heat source cannot cover the immediate demand at every moment. Whether it is a heat pump with output limited by outside temperature, a solar collector system dependent on the intensity of sunlight, or a boiler that operates more efficiently in significantly long intervals – all these situations require a thermal energy storage tank, into which energy is accumulated and from which it is drawn as needed. However, the installation of such a tank is not just about "connecting a pipe". It is a complex technical intervention that will affect the hygiene safety of the water, the service life of the equipment, the energy efficiency of the entire household, and the comfort of its residents for many years to come.

In this article, we will explain the entire procedure in detail – from receiving the tank and selecting its location, through mechanical installation work, hydraulic connection, electrical connection and pressure testing, to the actual filling, air venting and first commissioning. We will also add practical notes from real customer cases, where we encountered errors that were later difficult to find and expensive to fix.

If you are still considering which tank to buy, we recommend reading our other articles in the Knowledge Center first: How to choose a hot water storage tank – volume, heat exchanger and other criteria and What volume of hot water storage tank do I need for my household. There you will find detailed calculation procedures and comparison tables that will help you choose the right volume before you start the installation.

1. Receiving and preparing the tank before installation

Inspection upon delivery

The first and absolutely essential thing is a thorough inspection of the tank upon receipt from the carrier. Larger tanks – for example, ZGIB 850 liter storage tank or ZGIB 1000 liters – are transported on pallets and are usually wrapped in protective film. Before signing the delivery note, always check:

integrity of the outer packaging and thermal insulation (if delivered separately)
integrity of the pipe connections – none of them must be bent, deformed or cracked
presence of all flanges, plugs, anode inserts and other components according to the delivery note
absence of mechanical damage to the tank shell (dents larger than 2–3 cm in the weld area should be reported immediately)
readability of the production label with the serial number and pressure parameters – without it, you will not pass the inspection

If there is any doubt, we recommend immediately documenting the damage with a photo and noting the objection in the delivery note. Claims for damage not reported upon receipt are almost always rejected.

Transport to the installation site

Tanks over 300 liters are heavy and bulky – for example, ZGIB 1500 liters has a height of about 1 900 mm and a diameter of 960 mm, which significantly affects handling inside the building. Therefore, before ordering, measure:

width of all door openings along the route from the entrance to the boiler room
height of the ceilings in the boiler room and on the stairs
floor load capacity – 1 500 liters of water = 1 500 kg of water + the tank's own weight (usually 120–200 kg), totaling 1 600–1 700 kg on the base area of the tank
access for a hydraulic trolley or hand truck

For larger volumes, such as ZGIB 2200 liters, we always recommend planning the handling in advance – sometimes it is necessary to remove doors or directly use a platform and lower the tank through a window into the basement. For such volumes, it is also advisable to consider whether it is more convenient to place the tank outside the building (or in a technical shaft) – more on this is discussed in the article Dimensions and space requirements of hot water storage tanks 500–3000 liters.

2. Selection and preparation of the installation location

Requirements for the boiler room and technical room

A hot water storage tank must be placed on a flat, firm and dry base. The floor must have a minimum load capacity corresponding to the weight of the filled tank – in practice, for larger volumes, this means a concrete slab of at least 150 mm thickness or an existing reinforced floor. Never place the tank on wooden floors without prior static assessment.

Other space requirements:

Temperature: the boiler room must be heated to at least +5 °C in winter. Freezing of a filled tank will cause catastrophic damage – deformation of the shell, cracking of heat exchangers and devaluation of the anode protection.
Drainage of condensate and possible overflow: there must be a floor drain under or near the tank, or a catch basin with a volume of at least 10 % of the tank content must be created. This is a requirement of many insurers.
Service access: at least 600 mm of free space must be maintained on the side where the anode inspection opening and heat exchanger pipe connections are located. For tanks with an electric heating element, additional space must also be left to pull out the element – usually 400–600 mm.
Ventilation: in a boiler room with a gas boiler or other combustion source, ventilation is regulated by the applicable standard. In the case of a purely electric system, natural ventilation is sufficient, but humidity must not exceed 70 % in the long term.

Mounting the tank and leveling

The tank is placed on a rubber anti-vibration pad of 5–10 mm thickness (prevents noise transmission to the structure and protects against point corrosion of the bottom). Using a spirit level, check the vertical position in both axes – a deviation greater than 3 mm/m is not acceptable, as it disrupts the function of the gravity sediment drain valve and can cause incorrect temperature readings.

With the HPWB3000 tank, which is mainly used in larger households and small businesses, the installation of the tank and its static securing are even more important – with a volume of 3,000 liters and a filled tank weight exceeding 3,200 kg, any misalignment can cause instability of the entire unit.

3. Hydraulic Connection – Step by Step

Basic hydraulic circuit diagram

Preparation of pipes and fittings

Before the actual connection, prepare the following fittings and components – this is a minimal but safe set for every TUV tank installation:

Check valve on the cold water before the inlet to the tank (prevents hot water from flowing back into the water supply)
Safety valve with a set pressure of 6–8 bar (according to the tank's technical sheet) – mandatory safety fitting
Closing ball valves on each connection of the heat exchanger and on the primary circuit (allow service without draining the entire system)
Pressure gauge – visible from the usual working position, range 0–10 bar
Expansion tank – the volume is dimensioned to 10–15 % of the primary circuit content (including the tank if the primary is closed)
Thermohydraulic valve (combined safety and temperature valve) – if the manufacturer does not require it as part of the delivery, check the approved certification for potable water
Filter on the cold water – protection against sediments and rust from the water supply
Drain valve – on the lowest connection of the tank, with a discharge leading to the sewer or a floor drain

Procedure for hydraulic connection

Step 1 – Cold water connection: Cold water enters the lower part of the tank – the principle of stratification (layering of temperatures) requires that cold water is always supplied from below to avoid mixing of cold and hot layers. Along the route from the water supply pipe to the tank, install in this order: closing valve → filter → check valve → safety/pressure relief valve → inlet to the tank.

Step 2 – Hot water draw-off: Hot water output is always from the top of the tank, where the hottest layer is located. Before the outlet, install a sampling valve (allows water sample withdrawal) and continue to the household distribution. If a circulation loop is included in the design, its inlet (return) leads to the middle or lower third of the tank.

Step 3 – Primary circuit of the heat exchanger (heat source): The inlet and return connections of the heat exchanger are connected according to the labeling on the tank (usually IN and OUT or with arrows). A mistake in the connection direction (reversed circulation) is quite common and causes the heat exchanger to operate at only part of its capacity. The flow direction is always from bottom to top (hot medium enters from the bottom of the heat exchanger, the return leaves from the top). On each connection of the heat exchanger, there is a ball valve + thermostatic control valve or control fitting according to the heat source used.

Step 4 – Electric heating element (if installed): Most tanks have a preparation (plug connection) for an electric heating element with a power of 2–6 kW. This element serves as an auxiliary or backup heat source. It is mounted before filling the tank – after filling, it is not possible to push the element through the top connection without special tools. The element must be equipped with its own thermostat and thermal fuse (protection against dry running).

4. Electrical connection and control

The electrical part of the installation includes several components:

Temperature sensors (thermostats / PT1000 probes): Installed in plug connections at specified heights – usually one in the lower third (lower sensor for minimum temperature evaluation) and one in the upper third (upper sensor for charging control). In systems with a heat pump, up to three sensors may be installed.
Circulation pump of the primary circuit: Connected to a separate circuit with circuit breaker protection. Control is carried out via the boiler/HP control system or an external controller.
Electric protective anode: If the tank is equipped with an active (electric) anode instead of a passive magnesium anode, it is necessary to connect a protection transformer and configure the current protection according to the manufacturer's instructions.
Control system: Modern boilers and heat pumps have an input for an external TUV storage tank directly in the control unit. Programming of TUV heating priority over CH (central heating) is crucial for proper operation with heat pumps – TUV heating always takes place at a higher condenser temperature, which reduces COP.

5. Magnesium anode protection – installation and setting

The magnesium (passive) anode is a consumable component that is electrolytically dissolved instead of the steel tank shell. Most manufacturers supply the anode separately or install it into the inspection opening at the top of the tank. Installation procedure:

Check that the anode is made of certified magnesium material (the presence of a certificate for drinking water is mandatory)
Wrap the anode thread with Teflon tape (2–3 turns) or use a sealing compound suitable for drinking water
Screw the anode in with a torque wrench to the value specified by the manufacturer – over-tightening will damage the tank thread
Note the installation date of the anode – it is recommended to check its condition every 1–2 years, and replacement is usually required every 3–5 years depending on water hardness (more in the article Maintenance and service of TUV storage tank – what and how often to check)

From practice: in areas with very hard water (over 30 °dH), we have recorded anodes corroded by 60 % after only 18 months. The customer was surprised, but this is normal – the anode is doing its job. Problems arise when it is not checked for 5–7 years and only a rod without magnesium remains in the tank.

6. Pressure test and tightness check

The pressure test is a mandatory part of the installation and is documented by an entry in the installation report. The procedure is as follows:

Close all outlet and service valves except the vent valve at the highest point of the system.
Connect a pressure pump (manual or electric) to the filling opening and start slow filling with water. Keep the vent valve open during filling until a continuous stream of water without air bubbles flows out.
Close the vent valve and slowly increase the pressure to 1.5 times the maximum operating pressure. For tanks with a maximum operating pressure of 6 bar, the test pressure is 9 bar.
Maintain the test pressure for at least 30 minutes, checking the pressure gauge every 5 minutes. A pressure drop greater than 0.5 bar indicates a leak.
Visually inspect all connections, nozzles, heat exchanger flanges, and weld seams – mark any wet areas or drops immediately.

From practice: the most common leaks occur at threaded connections of nozzles, where the installer used too little Teflon or forgot the sealing ring. The second most common location is the heat exchanger flanges, where an incorrect gasket thickness was used. These errors can be quickly corrected – much worse is when the leak is discovered only after the insulation is closed.

7. Thermal insulation of the tank

Most tanks are supplied with removable plastic insulation of 60–100 mm thickness made of polyurethane foam or mineral wool. The insulation is installed after the pressure test and after the complete hydraulic connection. Important guidelines:

Insulation must not restrict access to inspection openings (anode, drain valve)
All supply pipes for at least 500 mm from the tank nozzle must be insulated with the same thickness as the tank
If the boiler room is unheated or only heated to 5–8 °C, additional external insulation (an additional jacket made of technical foam rubber) is recommended
Heat gain from an uninsulated tank in a warm environment can be significant (e.g. in a heated basement) – in such a case, tight insulation is less critical

More about correct insulation and its energy impact can be found in the article Insulation of TUV storage tank – why it is important and what to look for when choosing.

8. First filling, air venting and commissioning

First filling procedure

After the pressure test and installation of insulation, the tank is filled for good. Open the cold water supply, let the tank fill slowly and continuously vent the system. Air venting takes place at the following locations (in order of priority):

The highest point of the TUV distribution (usually on the last rising pipe)
Automatic air vent on the outlet from the heat exchanger to the primary circuit
Manual air vents on circulation pumps
Thermostatic valves on radiators (if the system is integrated with heating)

First heating – controlled start-up

Before starting heating, check that:

All shut-off valves are in the correct position (open where necessary, closed where necessary)
The circulation pump of the primary circuit is functional – check the shaft manually via the air vent screw
Temperature sensors are mounted in the correct nozzles and connected according to the diagram
The safety valve is clean (not blocked by a transport plug)

We set the first heating manually to the target temperature of 60 °C and monitor the temperature increase using the thermometer at the outlet and the sensors. The system should reach 60 °C within 2–4 hours (depending on the heat source's power and the tank's volume). If the increase is significantly slower, the cause is usually air in the heat exchanger, reversed circulation direction, or insufficient heat source power – for more information on connecting to a heat pump, see the article Connecting a hot water storage tank to a heat pump or boiler – how to do it.

Thermal disinfection

Immediately after the first filling, it is mandatory to perform thermal disinfection of the system – heating to at least 70 °C for at least 30 minutes. This procedure destroys any Legionella pneumophila bacteria that may be present in the new system. Some control systems (e.g., from heat pump manufacturers) have an automatic "anti-Legionella heating" function – make sure it is activated and repeats cyclically (recommended frequency is once a week).

9. Documentation and inspection

Complete installation documentation is not just bureaucracy – it is the basis of the warranty, insurance, and any potential service intervention in the future. The installation file should include:

A copy of the tank's technical data sheet with the serial number
A hydraulic connection diagram (even a hand-drawn one with dimensioned measurements is sufficient)
A pressure test protocol with the achieved pressure, duration, and result
Date of the first heating and thermal disinfection
A list of installed valves with parameters (safety valve: manufacturer, setting, certification number)
Date of installation and dimensional description of the magnesium anode (length, diameter)
Signature of the responsible installer (for larger systems, also a person authorized for pressure equipment)

In the case where the system is part of a larger building or is funded by a grant (e.g., the "Obnov dom" program), an inspection body may require a pressure tank inspection – prepare for this in advance.

10. Typical installation errors from practice

Over the years of working with customers, we have seen dozens of systems that did not function properly not because the tank was bad, but because something was wrong with the installation. Here is a list of the most common mistakes:

Reversed connection direction of the heat exchanger – the heat medium enters from the top instead of the bottom. Result: the heat exchanger only transfers heat in the top third, stratification is disturbed, and the tank "heats" to 45 °C instead of 60 °C.
Missing check valve on the cold water supply – hot water returns into the water supply pipe, resulting in hot water from taps marked "C" (cold).
Too small expansion tank – the safety valve discharges several times a day (dripping), which shortens its lifespan and causes limescale buildup under the valve.
Uninsulated supply pipe – heat loss on long runs can account for 15–20 % of the total energy input into the tank.
Forgotten thermal disinfection – the risk of Legionella is real, especially if the new tank is stationary for a long time before the first heating.
Incorrect placement of temperature sensors – the controller turns off the heating too early (sensor in the hot zone) or too late (sensor too low).
Minimum service distances not respected – the tank cannot be descaled later, the anode is inaccessible, and the heat exchanger cannot be cleaned.

Most frequently asked questions (FAQ)

Can I install a hot water storage tank myself, or do I need a professional?

It depends on the scope of work. A skilled owner can handle bringing and placing the tank. Connecting the hydraulic system to the existing drinking water supply should be done by a trained plumber who can issue an installation protocol. The electrical part (pumps, sensors, control units) belongs exclusively to the hands of an electrician with the appropriate qualifications. A pressure test and its protocol should always be signed by the responsible installer – otherwise, the manufacturer's warranty may be void.

What pressure should the water have during filling and operation?

The operating pressure of the TUV system is usually 3–6 bar, with the safety valve set to the maximum pressure (e.g., 6 bar). The minimum operating pressure should not drop below 1.5 bar during full withdrawal – at lower pressure, valves that do not expect this may open, and air venting becomes more complicated.

When should the first service be performed after installation?

We recommend the first inspection after 12 months of operation: checking the condition of the anode, visual inspection of seals, checking the safety valve (manual discharge), and checking the temperature setting and anti-Legionella cycle. Further service intervals are usually 2–3 years. A detailed service plan can be found in the article Maintenance and service of a hot water storage tank – what and how often to check.

What to do if the safety valve drips after filling?

Dripping from the safety valve immediately after filling and heating is normal – water expansion from 10 to 60 °C increases the volume by about 2 %, which must be released somewhere. If the dripping stops after the temperature stabilizes, it is normal behavior. If the valve continues to drip, the cause is either an undersized expansion tank or an input water pressure that is too high (over 4.5 bar) – in this case, a pressure-reducing valve should be installed at the inlet. Never block the safety valve – it is a safety component.
Is it possible to connect a tank so that it is heated by a boiler and a solar collector simultaneously?

Yes, this is exactly what tanks with two heat exchangers are designed for – the lower heat exchanger is primarily intended for a low-temperature source (solar, heat pump) and the upper heat exchanger for a bivalent source (boiler, auxiliary source). Each heat exchanger has its own circuit with a circulation pump and control. It is important to ensure correct hydraulic separation of the circuits – without check valves and control valves, heat transfer in the opposite direction could occur. For more information on this topic, see the article Hot Water Storage Tank with One or Two Heat Exchangers – What is the Difference.

How long does the installation of a standard 1000-liter tank take?

For an experienced installer with a prepared location and complete materials, the realistic installation time is 6–8 hours for a simple system (one source, one point of withdrawal). If it is a more complex system with two heat exchangers, a solar circuit and integrated control, expect 1.5–2 days of work. Add to this the time required for the initial heating, bleeding air and setting up the control.

Conclusion

The installation of a hot water storage tank is a complex process consisting of a series of interrelated steps – from selecting the right location and receiving the equipment, through hydraulic connection, electrical connection, pressure test and thermal disinfection, to documentation and handover into operation. No step is superfluous and each has its function, which will become apparent either immediately or after years of operation.

If you have already decided on a specific tank, but are still considering the volume, take a look at our range – for example, ZGIB 850 liters for smaller households with a heat pump, ZGIB 1000 liters as a standard solution for a family home, or for higher demands even ZGIB 2200 liters for larger premises or combined systems. Each of these tanks can be connected according to the procedure described in this article – with minor differences depending on the specific configuration of the heat exchangers and connections. Any questions about typical faults are also answered in our next article Common Faults of Hot Water Storage Tanks and How to Recognize Them and a comprehensive overview can be found in the section Common Questions about Hot Water Storage Tanks.

Do you have a question about this topic?

Having difficulty making a decision or dealing with a specific situation in your household? Write to us – we will be happy to help.

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