Using rainwater with the Einhell submersible pump

Every time it rains, the roofs of our houses can collect thousands of litres of clean water, which is usually trickled away unused into the ground. This water is particularly well-suited to watering the garden, since it doesn't contain lime or other water additives such as chlorine.

Why not a rain barrel?

The simplest approach to rainwater storage is the common water butt, which I also used for years. However, the following disadvantages drove me to move to an underground storage option:

  • limited capacity—even large water butts rarely hold more than 1000 litres
  • large space requirement
  • not visually appealing


Some things had to be considered before getting hands on. On the one hand, the tank should have a capacity of at least 3000 litres, so that it can cover long dry periods. On the other hand, I did not want to have to dig too deep, because the installation location did not allow the use of an excavator. In the end, I decided on two shallow 1800 litre water tanks connected together.

Since the technology should remain largely invisible, I selected the Einhell GC-DW 900N submersible pump, in combination with an external pump control system.

Here's a simplified schematic of the whole system:


Before the digging could start, a few paving slabs including concrete edging stones had to be moved. This is child's play with the Einhell RT-RH 32 hammer drill. After 18 cubic metres of excavation (and a few callouses on the hands), both tanks were laid on a gravel bed in the pit and connected. Before the filling material was laid on top, it was a good idea to check the system for leaks and function.

How it works

The rainwater drains through the downpipe and through a sieve filter into the tanks. These are connected to one another and fill up evenly. If they are full, the excess water is carried through the overflow to a soakaway. The Einhell submersible pump sits in a pump recess in the bottom of the tank at a depth of around one metre and pumps the water through the pump control system, to which the 25 metre long garden hose is attached.

Conclusion after using this for one year

The system has been running for a year now and I am extremely satisfied with it. The GC-DW 900N performs very reliably and above all quietly. Even if the fuel cap is open you can not hear it. With 3.4 bar delivery pressure, I notice at the end of the garden hose no difference to the house water pipe.

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Written by Philipp Weiler
Published on 26.04.2018

From professional to professional: With their expertise in garden care, our garden specialists help you create your perfect green oasis. Philipp Weiler is a freelance blogger and a passionate hobby gardener. Whether it's lawn care, hedge trimming, or irrigation – in his blog posts, you'll find all the essential information about Einhell devices for the garden and terrace.