RTMO-Erdspeicher wird in Garten eingebaut

Size of installation

How big your rainwater harvesting system should be

Domestic water use
A tank volume of approximately 1,000 liters is required per person for domestic water use.

Garden watering
For every 150 m2 of intensive irrigation area, a tank volume of approx. 1,000 liters is assumed.

Roof surface
To determine the required roof surface: for every 1,000 liters of tank volume, approx. 20-25 m2 of roof surface should be available.

Installation rainwater tank

Calculation example 1

Mr. Practical would like to purchase a simple rainwater harvesting system for garden irrigation at the lowest possible financial cost. His property area is 600 m², of which the house occupies 100 m².


Garden Eco 4,000 litres


The roof surface is suitable to fill a tank of 4,000 litres. The system is a budget option and the extensive garden irrigation requires a tank of this size.

Calculation example 2

The Richards family has a house with 200 m² roof area. They would like to have a system with service water utilization and to a small extent also for the irrigation of their vegetable garden. Four people live in the house. The family would like to have no work later with the plant and invest no time for the maintenance.


Home and garden comfort 5,000 litres


The roof area is quite sufficient for 5,000 litres. The system is a comfortable option, for domestic water use calculate about 4,000 litres for four people, plus some garden, which adds up to 5,000 litres.