Underground rainwater harvesting
Practical Action
Covering the top of the underground tank
1. Using earth bricks mark the inlet and outlets of your tank from both ends of your tank.
2. Lay your wooden poles across your tank spaced at 2m.Ensure that the poles are not
totally fixed for ease removal during maintenance usually during the dry season.
Root zone depth
Picture 2: Preparing to ram the bottom of the
underground tank ©Practical Action/Douglas Gumbo
3. Decide where you can place two openings at the top for collecting and checking water
inside your tank.
4. Lay old plastic or hessian bags onto the poles.
5. Use same mortar as referred above to plaster the roof of your tank.
Picture 3: Tank lining/ Plastering
©Practical Action/Douglas Gumbo
Water conveyance devices
Fittings are usually built into the tank during construction. These include:
one or more outlets for water collection;
a drainage tap (or wash-out) at the bottom of the tank, to be used when cleaning;
an inlet pipe; and
an overflow pipe. This must be screened to prevent insect entry.
Some advantages of using underground rainwater storage tanks
Rainwater is generally much lower in salinity than other water. This is good for plants in
the garden and fields.
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