Hot water supply plays a central role in modern buildings — but how does it remain efficient and convenient? An inconspicuous system ensures that there is no need to wait for hot water. Discover what technology is behind this comfort and why it is being used more and more frequently.

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What is a circulation line?

A circulation line is a system within the hot water supply that ensures that hot water is quickly available at all times. It connects the hot water tank to the extraction points and returns unused water to the storage tank. This ensures a constant availability of hot water.

Why is a circulation line used?

A circulation line ensures that hot water is delivered quickly and efficiently. It increases comfort, saves resources and improves hygiene in the hot water supply. It offers decisive advantages, particularly in buildings with long lines.

• Improving hot water comfort: The constant circulation of warm water means that there is no need to wait for taps and showers. Hot water is immediately available. This is particularly noticeable in large houses or apartment buildings.
• Saving water and energy: Since no cold or cooled water has to drain before hot water is available, less water is wasted. This saves resources and lowers operating costs, particularly when used in an energy-efficient manner.
• Hygiene benefits: The circulation line prevents stagnant water in the pipes, which could promote the formation of legionella. The constant movement of water and the ability to control the temperature significantly improves hygiene in the hot water supply.

When does a circulation line have to be installed?

In certain cases, the installation of a circulation line is required by law for drinking water hygiene. According to the requirements of DIN 1988-200 and the Drinking Water Ordinance (TrinkwV), a circulation line is necessary in buildings with a central hot water supply if the storage capacity exceeds 400 liters. It must also be installed if the pipeline capacity between storage tank and removal point exceeds 3 liters.

This regulation is aimed at preventing legionella formation and is intended to ensure hygienic operation.

How does a circulation line work?

A circulation line ensures that hot water circulates continuously in the pipes and is immediately available. To do this, it works with a closed circulatory system, which is kept moving by a circulation pump.

The hot water flows from the hot water tank to outlets such as taps or showers. If the water is not used, it is returned to the storage tank via an additional line, where it is reheated. This constant movement ensures that no water cools down or is wasted unnecessarily.

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A central role is played by circulation pump, which continuously moves water in the system. In order for the system to work efficiently, it is often powered by a thermostat controlled. It monitors the water temperature and only activates the pump when needed. This saves energy and at the same time ensures a constant temperature throughout the circuit.

In addition, a high-quality Line insulation essential to minimize heat losses. As a result, heat is retained in the system and efficiency is significantly increased. The combination of continuous movement, temperature control and insulation makes the circulation line an important part of a convenient and hygienic hot water supply.

How is a circulation line laid?

The installation of a circulation line is carried out parallel to the regular hot water pipes and requires careful planning. The installation usually takes place during the construction phase of a building, but can also be implemented retrospectively in existing systems.

Here's how it works step-by-step:

1. planning: Determine the route and select the materials.
2. Line laying: Installation of the circulation line parallel to the hot water pipe.
3. pump installation: Integration of the circulation pump, usually near the hot water tank.
4. isolation: Wrapping pipes with insulation material to minimize heat losses.
5. controller: Connect a thermostat or timer for temperature control.
6. startup: Test for tightness and function of the system.

Can a circulation line be retrofitted?

Existing buildings can be retrofitted to a circulation line, but this requires structural adjustments and careful planning. In addition to laying additional lines, a circulation pump must be installed and the system must be professionally integrated. If major construction measures are not possible, alternative solutions such as special pump systems with return valves can also be used.

How much does that cost?

Retrofitting a single-family home costs between 1,500 and 3,000 euros, including material and labor costs. A circulation pump costs around 100 to 300 euros. There are additional costs of 15 to 45 euros per meter for cables, including insulation. The ongoing operating costs due to the power consumption of the pump amount to around 20 to 50 euros per year, depending on the efficiency of the pump and the operating time.

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When is a circulation line worthwhile?

A circulation line is particularly worthwhile in buildings with long lines, as it reduces waiting times for hot water and increases comfort. It is almost indispensable in apartment buildings with several outlets. In single-family homes, it is particularly useful for large plots of land or water taps located far away.

Usage behavior also plays a role: When using hot water frequently, the circulation line saves time and resources, while it can be less economical when used sporadically.

What are the advantages and disadvantages of circulation pipes?

Circulation lines offer the advantage that hot water is always available. This increases comfort and improves hygiene. However, they involve higher installation and operating costs, which should be considered carefully.

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What alternatives are there to a circulation line?

There are several alternatives to circulation pipes, which can be a useful solution depending on the type of building and hot water requirements:

• Decentralized water heating: Hot water is produced directly at the extraction point, for example by instantaneous water heaters or small storage tanks. This method minimizes heat losses and is particularly efficient in buildings with few extraction points.
• Hot water pipes with return valve: Here, the cooled water is returned to the cold water pipe so that no water is wasted. This solution is less complex than a circulation line, but not as convenient.
• Timers or smart pump systems: By using a circulation pump that only works when needed or within fixed time windows, operating costs can be reduced without sacrificing the benefits of circulation.
• Potable water heating machines: These devices provide hot water directly at the extraction point without the need for additional pipes or pumps. They are particularly suitable for small applications.

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