The hot water quality can be adversely affected, even when the cold water is microbiologically pure. For example, Legionella can bread if temperatures of less than 55 °C occur in the hot water.

To ensure drinking water quality in hot water, the following measures should be taken:

Circulation Systems when the Pipe Volume exceeds 3 Litres

When the pipe volume exceeds a volume of 3 litres between the outlet of the hot water tank and the outermost extraction point, circulation systems should be installed – either as a parallel system or an internal circulation pipe. These should be calculated in such a way that the water temperature in the circulating system does not drop more than 5 K below the tank exit temperature (60°C/ 55 °C).

Circulation systems should be balanced with regulating valves either completely or in parts of the system. The following is required for the design of such a system:

• Determination of the required circulation volume flows through the heat loss of the pipes
• Determination of a temperature difference of max. Δt 5 K
• Specification of an available pipe friction pressure gradient
• Hydraulic balancing of favourable circulation circuits through the pipe diameter, taking s maximum permitted flow rate into account

Up to a Pipe Volume of 3 Litres

With a water volume of up to 3 litres, a circulation pipe is not necessary. The volume of 3 litres per pipe section without circulation should be regarded as a maximum volume. For reasons of hygiene, the water volume should be kept as low as possible.

Insulation

In all types of buildings, the hot water pipes should be insulated with an insulating layer that fulfils the minimum requirements of EnEV (in Germany). National regulations should be observed.

Flushing Systems in the Hot water Supply

A flushing system is neither economically nor hygienically recommended for hot water provision because

• Pure hygienic conditions are present in the circulation.
• In the cooled hot water of the branch line, there is no excessive bacterial breeding.
• The user does not use cooled hot water.
• The branch line is thermally disinfected during use.

Viega System Solutions for Hot water Supply

• Smartloop Inliner Technology: Internally fitted circulation system with flexible circulation pipes in metallic branch line.
• Easytop Circulating Regulation Valve for the regulation of the volume flow in normal operation and during thermal disinfection.

Read also

• Type 0: Use rarely interrupted
• Type 1: Interruption in use on a room/apartment basis
• Type 2: Interruption in use on a storey basis
• Type 3: Interruption in use on a building basis