Cold Water Circulation

The design hurdle

Flaws in cold drinking water

Preventative planning and a design with a hygienically beneficial installation type are good prerequisites for complying with the intended use and maintaining drinking water hygiene in the building. Even a fault in regular water exchange can be eliminated with suitable flushing devices which ensure automated forced withdrawals. But what is to be done when regular water exchange is insufficient to guarantee that temperature is constantly maintained in cold water?

Hazards: Drinking water temperature

In addition to preventing stagnation, temperature maintenance in hot and cold water is essential for maintaining drinking water hygiene. Lukewarm temperatures between 25°C and 50°C provide ideal breeding conditions for microorganisms.

The cold water temperature must therefore be kept below 25°C in all pipe sections.

You can learn more about the temperature limits in drinking water here.

External and internal heat loads can seriously hinder temperature maintenance in cold water!

Internal heat loads

High heat loads in installation areas

Heat sources such as hot water pipes in plumbing and heating systems and components in electrical and ventilation systems lead to a rise in temperature of the drinking water pipe.

Even with insulated pipes, cold drinking water can absorb this heat and reach hygienically critical temperatures in a short amount of time. In this context, laying cold and hot water lines in combined shafts is particularly problematic.

External heat loads

High ambient air temperatures

High external air temperatures can cause ambient air temperatures of more than 25°C in buildings without air conditioning. In the event of stagnation, cold-water temperatures below 25°C can no longer be achieved as a result.

Incoming main water temperatures

Where drinking water is sourced near ground level in the summer months, the temperature of water fed into drinking water installations is higher (>20°C), reducing the maximum tolerable stagnation time even further.

Climate change and water shortage

Climate change will cause environmental and incoming main water temperatures to rise even higher, contributing to the increase in cold water temperature. Along with climate change, there is the problem of water shortage. The amount of water available will become increasingly limited in the future and should be used sustainably.

High flushing amounts: Economy and ecology

The usual solution to reduce the cold water temperature is to flush out the heated drinking water. However, considering external temperatures are dictated by the time of year, it is obvious that the situation comes to a head in the summer months in combination with the influence of climate change. Increasing external temperatures lead to increased ambient air temperatures in the building and also raise the incoming main temperature of the drinking water.

As a result, the frequency of temperature-controlled flushing measures is increased dramatically. Enormous flushing amounts are used for these flushing measures which, despite these amounts, are no longer effective.

Practical example

Effect of external air temperature and ground temperatures on flushing volumes of a hospital without air conditioning

If the cold-water temperature of 24°C is exceeded, a system in the building will automatically trigger a flushing process which will end once 20°C has been reached. The aim of this measure is to keep the temperature of the cold water below the specified 25°C.

In the winter months, the trigger temperature is rarely reached, which is reflected in the lack of flushing processes for the purpose of temperature maintenance. However, in the summer months, high temperatures can cause a massive increase in flush volumes up to 16,000 l/day!

Cold water circulation: Flushing volumes of a hospital without air conditioning

The solution: Cold water circulation

Permanently cold drinking water up to the tapping point

In many buildings, sustainable and economically justifiable protection against unacceptably high cold-water temperatures is only possible with cold water circulation with cooling. KHS CoolFlow cools the drinking water to precisely 15°C. The circulation volume flow is controlled in such a way that the recirculated drinking water is 20°C. In addition to temperature maintenance, water exchange is essential for maintaining drinking water hygiene. KHS CoolFlow balancing valve technology can ensure the water exchange required by the relevant standards. Active temperature maintenance ensures that temperatures <20°C can be achieved, even in buildings where thermal separation is only possible to a limited extent or where there are high heat loads in most installation areas.

In a cold water circulation system with KHS CoolFlow, there is less microbiological growth, and flushing volumes are sustainably reduced to a minimum.

Cold water circulation