OFF GRID Rainwater Harvesting – 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.

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.

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

YouTube player

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

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

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

(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.

(Disclaimer: As an Amazon Associate I earn from qualifying purchases. Thank you for helping to support my content this way. )

tank sitting on gravel base animation

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

animation showing the assembly of tank surround

Posts and Rails

2×4 and 2×6 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.

Build the Forms

making the concrete forms from 1x8 lumber

I’ll build the forms from 1×8’s. With the inside form walls made in two pieces.

making the concrete forms from 1x8 lumber

They have a 45 degree cut to make stripping the inside forms easier.

making the concrete forms from 1x8 lumber

A mending board across this cut will hold the form together during the pour.

Building the Outer Form Walls

assembling the concrete forms

Cleats added to these 1×8’s will make attaching stakes easier as well as clamping the forms together on the ends.

assembling the concrete forms

And then I can screw the outside form walls together.

Rainwater Harvesting System - locating the forms off the pavilion

And I’ll line up this wooden box to the pavilion piers.

Secure Form Walls with Stakes

setting concrete forms in place and securing with stakes hammered into the ground

Then pound in stakes and screw them to the form cleats.

OFF GRID Rainwater Harvesting System - levelling forms for concrete

Checking and adjusting for level and square as I go along.

squaring forms with a tape measure corner to corner

Then the inside walls are clamped then screwed together.

assembling the concrete forms

Inner Walls added, Squared, and Levelled

They are levelled and squared and temporary spacers added.

OFF GRID Rainwater Harvesting System - levelling forms for concrete

Some of the stakes were too tall so I trimmed them with a hand saw.

sawing the form spikes down

With the forms in place I then add the pipes to the dry well.

Shopping Cart
Scroll to Top