Building a sand base for a water tank

This month I took delivery of the first of two very large water storage tanks. To save some dollars I decided to mount the tank on a sand pad – as an alternative to concrete. Finding good instruction on the web proved difficult so here I have assembled my  process of laying out a sand pad for a tank diameter of 3.5m.

The pad needs to be at least 1m larger in diameter than the tank itself which will give you a 500mm perimeter edge. The ground should be as level as possible, in my case I chose to build up the low side of my site instead of digging down into rocky soil – with hand tools. A bobcat would make quick work of the whole process, but that only adds more cost. Working with hand tools and accomplishing jobs like this is completely satisfying.

So the tools I used were; Tape measure, Rope, wooden stake, line marking spray paint, hammer, petrol powered edge trimmer, shovel, hoe, rake, 4m length 2×4 pine timber, long spirit level, 100mm plastic garden edging, 15 small stakes.

Using this formula, work out the volume of sand you will need. My tank supplier recommended 100mm sand depth for a steel tank. Volume = Pi x radius squared x height.  Pi is 3.1459.

Also needed is  a quantity of 10mm aggregate for around the bottom of the tank once in place. This is so water that drips off the top of the tank does not pool and cause erosion.

The garden edging length can be worked out with this formula – Circumference = Pi x diameter

  1. Choose your site and hammer the wooden stake in the center of the site. Tie one end of your rope in a loop and place it over the stake letting it drop to ground level. Measure the radius you need and pull the rope taught to the same length. Mark the length on the rope with your spray paint. Keeping rope tight hold spray can at the mark on the rope and slowly walk in a circle spraying a line as you walk around the stake. You should now have a very evenly painted circle.
  2. Using the edge trimmer cut within the circle working from the edge in and remove as much grass as possible down the the bare soil. Rake the cuttings up and use them to mulch the nearest garden bed.
  3. Place the 100mm garden edging on the perimeter and hold in position with small stakes, later to be removed.
  4. Use the length of pine on the top edge of the garden edging and place the spirit level ontop – working between the center of your circle out to the edge – work out if your site is level or not. Construct any retaining walls necessary to create a level pad. I used rock that I had collected and back filled it with the aggregate.
  5. Get the delivery of sand dumped into the center of your circle to make it easier to spread out. Use the 100mm edge as your depth guide and spread as evenly as possible. I used the hoe to tamp down the sand to compress it into place.
  6. Use the length of timber and spirit level to level out the pad. The timber can be used to pull sand around – work backwards so you cover your tracks.
  7. Once level the tank can be put in place and the 10mm aggregate spread around the remaining perimeter. This is so when the rain drips off the top of the tank it prevents the sand from being eroded away it also makes the surface more stable to walk on.

And that’s it! If you found this information helpful show your appreciation and hit LIKE. Thanks

3 responses to “Building a sand base for a water tank

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