Why is shower wastewater such a valuable heat source?

Shower wastewater contains a lot of thermal energy because it is still warm when it leaves the shower.

Consider a typical example:

• Shower flow: 8 litres per minute
• Incoming cold water: 10°C
• Wastewater entering the heat exchanger: 38°C

There is a temperature difference of 28°C between the two water streams.

At 8 litres per minute, that represents a continuous flow of warm water carrying heat away from the shower.

Without heat recovery, that heat simply disappears into the drain.

With a shower heat exchanger, a large part of it can be recovered immediately.

And because the hot wastewater and cold incoming water flow at the same time, there is no need for a large thermal storage tank.