DIY Water Tank

An inexpensive ferro cement water tank that is simple to make for the home handyman. Construct a 5000 litre tank for a lot less than an equivalent tank

The materials used in the construction of this ferro cement tank are of the type readily available. Requiring two people, preferably three, in the final stages, building a tank like this provides an opportunity to practise neighbourly co-operation.

The project is best carried out in Autumn. The cooler, humid weather makes for longer drying and a stronger job.

Because the tank needs to be filled almost immediately it is completed, building it in Autumn means that precious water supplies will be replenished sooner.

Materials

6 metre light galvanized reinforcing mesh, 2 metre wide, 25 m (1 inch) square mesh birdwire, 1 m wide, roll tie wire, 4 boards, approximate 2.5m x 15 cm x 10 mm (1"x6"x4") (used as boxing for tank base), heavy reinforcing mesh, 2.5 m (1 inch) square, approximate 6 bags of cement and five times this volume of sand, small quantity of medium aggregate (for concrete base), 2 light poles, approx. 2.5 m long (1 inch), 375 g packet of washing soda (1/2 pound), large bucket, 25 mm (1 inch) gate valve, connected to 1 metre of pipe, 2 cement floats, several house bricks, old, soft broom, 15 cm (6 inches) whitewash brush, light stepladder, 200-litre (44 gallon) drum, wheelbarrow, cement mixer.

At a pinch, the cement mixer can be dispensed with, and a 200 litre drum (44 gallon) substituted for the stepladder.For the sake of speed, hire or borrow a mixer if you do not own one.

Level an area 3 m square and fix the boxing firmly to position.
Cement the heavy reinforcing mesh inside the square formed and raise it from the ground with the bricks, placed on their flats.
Make a tank form by shaping the galvanized mesh into a cylinder.
Keep the shape as even as possible - although it is not necessary to have it geometrically perfect.
Join the ends with tiewire, keeping the seams as flat as possible.
Fasten one end of the birdwire to the cylinder with the tiewire, in a different position from the seam in the mesh.
Pass the birdwire around the mesh, ensuring the edges are level.
Cut to length and tie off the end.
Go back and fasten the birdwire to the mesh at 15 cm intervals (6 inches), horizontally and vertically.
If it starts to buckle, undo one end.
It is important that the birdwire lies as flat to the mesh as possible.
Turn the form upside-down and repeat the process.
You will find that the birdwire overlaps in the centre of the form.
When the form stands upright, ensure that this overlap faces upwards.
Attach the wire to the inside of the form, using the same method.
With the surplus birdwire, make 'skirts' on the inside and outside of the form, about 15 cm (6 inches) from the bottom.
These skirts should hang at an angle of about 45 degrees to the form.
They will help 'tie' the tank to the base.
Cut a 25 mm (1 inch) hole in the form, 30 cm (12 inch) from the bottom.
This will take the gate valve at a later stage.
Tie the two light poles to the top of the form in a cross.
This is necessary to hold the form rigid whilst plastering.
Fill the base formwork with a concrete mix: 1 cement, 2 sand, 4 aggregate.
With a shovel, work the concrete vigorously to remove air pockets.
Assisted by a helper, place the tank form in the centre of the base, ensuring that it sits firmly on the reinforcing.
Check to see that you have the hole for the valve at the bottom, and it faces the right way.
Push the skirts well below the concrete.
When the base is 'surface dry', place the gate valve and pipe in position.
Support in place with a brick.
Make a small quantity of cement and sand, 1:4, and cement the pipe and valve in place.
Allow the concrete to dry enough to bear your weight.
Mix the plaster of cement and sand 1:4, dry enough to 'hang' on the form, yet moist enough to work smoothly.
This is where a third person is an asset.
He or she can mix the plaster whilst the other two build the tank.
Place the drum outside the tank and the ladder inside.
Dump enough of the mix inside the tank to enable work to proceed without interruption for as long as possible.
Stand inside the tank, with the other plasterer directly oppostite on the outside.
Working as quickly as possible, use the floats to spread the plaster on the form, working upwards all the time.
If the floats are used in opposition, more pressure can be applied.
The plaster should be no thicker than necessary to completely cover the framework.
Once the sides are completed, plaster the base.
Slope the bottom towards the form for greater strength.
Completely cover all wire. If any is left exposed, it will rust, weakening the tank.
In the large bucket. make up a cement-sand mixture at 1-1/2. Add enough water to enable it to be easily applied with the brush.
Add the washing soda, and mix thoroughly. Paint the tank with this slurry, inside and out. Climb out of the tank.
Using the soft broom dipped in the slurry, smooth off the base.
Within half an hour or so, the tank should be dry enough to fill.
Do this slowly and do not allow the water to play directly on the tank - run in onto an old sheet of iron or a bag.
Leaks can be stopped with a dry cement-sand mix at 1:1, or one of the proprietary fillers, such as Chemcrete.
After two or three days, remove the crosspieces.
Cover any exposed metal with a 1:4 cement-sand mix.
If required, the outside of the tank can be finished with a coat of paint.
Tanks more than 2 metres in diameter, need to be further reinforced with steel rod, placed around the sides.
Ferro-cement tanks should never be allowed to completely dry out.
A roof made with sheets of galvanised iron will keep the tank moist by condensation if the water level gets low.