OFF GRID Rainwater Harvesting System – Part 1 – concrete foundation

This is a continuation of my series on installing a rainwater harvesting system. In this post I’ll show the excavation and pouring of a low retaining wall, or curb if you like, for the foundation of this 500 gallon tank.

Off-Grid Rainwater Harvesting Tank in the garden
Off-Grid Rainwater Harvesting Tank in the garden

In the previous post I showed all the steps I took to install a 1200 gallon tank. This smaller tank sits in our garden and collects water from this timber frame style pavilion I built a few years ago.

This tank fill capture rain from this pavilion.
This tank fill capture rain from this pavilion.

And I’ll be adding an off grid 12 volt solar system and pump to supply the drip irrigation to beds and hanging planters around the pavilion.

Jump to:

Off-Grid Rain Tank Part 1 – Pour the Tank Foundation
Off-Grid Rain Tank Part 2 – Build the Tank Surround
Off-Grid Rain Tank Part 3 – Tank Plumbing and Fittings
Off-Grid Rain Tank Part 4 – Install a Solar Powered Pump

OFF GRID Rainwater Harvesting Tank - poured concrete & gravel foundation
Watch this video on YouTube.

See the Youtube Video Part 1 or Part 2 or Part 3 or Part 4

Off Grid Rainwater Harvesting System – PART 1: a concrete footing and gravel foundation

(this is a transcript from the video)

There will be some similarities in the installation of these two tanks so if you’ve already watched the first series then you may see me repeating a few of the steps. So I’ll try to move quickly here.
In the next few episodes I’ll detail the construction of the cedar and corrugated panels that surround the tank. And then cover all the plumbing and fittings to take rainwater from the pavilion and deliver it to the tank. Then finally I’ll install the solar panel and set up the pump and other off-grid electrical parts in a mini pump house at the back of the tank.

A flat and level spot is excavated behind the pavilion and a concrete curb is poured.

Rainwater tank footing animation

Then filled with pea gravel.

tank sitting on gravel base animation

4x4 posts sit in galvanized saddles that are secured to the curb with anchor bolts.

animation showing the assembly of tank surround

2x4 and 2x6 rails are added between these posts on all sides.

animation showing the assembly of tank surround

Corrugated galvanized panels are attached to these rails to complete the tank surround.

animation showing the assembly of tank surround

Excavating the Site for the Tank

So the real work starts with shovel and wheelbarrows — with the occasional break to pet a cat.

excavating a level place for the rain tank

When this spot is flat and level I then dig a trench for a drain.

levelling a spot in the garden for the tank
OFF-GRID Rainwater Harvesting - digging a drain trough

Water that accumulates inside the curb walls needs to drain away. This trench will move water from under the tank and to a dry well where it will absorb into the ground — more on that later.

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