ISSB Water Tank Consruction Manual 120908 FINAL[1]

INTERLOCKING STABILISED SOIL BLOCKS RAINWATER HARVESTING WATER TANK MANUAL 2,000 - 15,000 Litres

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TABLE OF CONTENTS: 1.Introduction.........................................................................................................................2 2. List of Materials...................................................................................................................3 3. Site Preperation...................................................................................................................4 4. Tank Foundation.................................................................................................................6 5. Wall Construction...............................................................................................................7 6. Inside Plastering and Waterproofing.................................................................................10 7. Fitting Wire Mesh and Outside Plastering........................................................................11 8. Roofing Tank.....................................................................................................................14 9. Veranda and Tap-Pit Area..................................................................................................17 10. Tank Maintanence...........................................................................................................18 11. Determining Tank Capacity & Equations......................................................................19 12. Sample Building of Quantities for 2,000-10,000L Tanks...............................................20

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1

Introduction

One of the main uses of Interlocking Stabilized Soil curved Blocks (ISSB) is to construct rainwater harvesting water tanks. Water tanks made from ISSB prove to be low-cost, more durable, and safely store water without contamination. Water tanks can be constructed both above and below ground from capacities of 2,000 litres to 150,000 litres. This manual covers above ground construction techniques ranging from 2,000 liters to 15,000 liters. Blocks are made from a mixture of subsoil (murram), water and oridinary portland cement (OPC). Depending on the soil type, sand may be added to the mixture. When making ISSBs for a water tank, one should produce around 100 blocks from one 50kg bag of cement. This number provides an estimate, however because soil types can differ greatly, the average number of ISSBs per 50kg of cement may vary between 100 and 120. It is advisable to create ISSBs on site and in an area that is in a near proximity to where the tank will be placed. In addition to the convenience that making ISSbs on site highlights, one of the key benefits of ISSB Technology, is that this feature reduces transport costs. Please refer to the Blockmaking and Machine Operational Manual for complete instructions on how to create blocks and care for the machine.

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2 1 2 2 2 2 2 1

List of Materials

Wheelbarrow Spades Hoes Trowles Spirit Levels Plumb Bobs Measuring Tape

2 2 1 1 10m 1 pair 1 pair varied

Mortaring Pans Wooden floats Metal float Line bar (straight edge) Building line Pliers Wire cutters Water

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Site Preperation A. Prior to building the tank, it is important to carefully select an area that is not only convenient to the users but also a site that allows harvesting the highest possible amount of rainwater from the roof surfaces. The tank should not be located under a tree.

B.

Place a peg at the centre of where the tank will be. Attach building line (string) to the peg and draw a circle, this will form the base of the tank. The length of the building line will be: the radius of the tank (radius is half of the diameter) + 30 cm (the approximate width of 2 blocks). For example: If you have a diameter of 3m, your radius would be 1.5m. So: 1.5m + .3m (30cm) = 1.8m 1.8m = the length of the building line. Sticks, leaves, etc. 4” - 8”

C.

Clear the area of all organic material. Remove the top soil until you reach hard soil, depending on the hardness of the soil, this depth will range from 4inches - 8 inches. Level this area. 4

4

Tank Foundation

A. Mix 2 inch aggregate with cement

and sand in an amount appropriate to the size and litre capacity of the tank. The ratio for this mixture should be 1:4:5 (Cement: Sand: Aggregate).

B.

Transfer this mixture to the where the foundation will be using a wheelbarrow. Each wheelbarrow of mixture that is poured in should be compacted using a bar line (straight edge) in a vertical motion.

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4

Tank Foundation

C. Once the mixture is compacted, use the bar line to level the mixture by sliding

across the surface. The aggregate should not be visible (poking out of the top) and the surface should be smooth. If an area is not level, add more of the mixture to the depressed areas.

D. Allow the foundation to dry for 1 day, which will ensure the concrete is firm enough to build on.

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5

Wall Construction

The section covers building the walls of the tank to the appropriate height. The walls should not be constructed until the foundation has had enough time to solidify and dry. Please read all steps before beginning.

A.

Without using mortar, lay the first course of blocks upsidedown around the edge of the foundation.

B.

Use a nail to mark the inside and outside circle around the ISSBs. This circle will help guide the mason to correctly lay the first course of ISSBs.

C.

Attach first course of blocks with 2 inches of mortar between the foundation and the block. The ratio for mortar is 3:1 (sand:cement). It may be helpful to make a groove in the mortar with a trowel that will allow space for the interlock. Continue for entire course. 7

5

Wall Construction Horizontal interlock

D.

Please note that blocks are placed so the horizontal interlock is facing downward (as seen here). Vertical Interlock

E. It is imperative that a spirit level is used on every block and every course that

is laid to ensure that each block and course is level. The spirit level should be used both parallel to the block (a) and perpendicular to the block (b). After the first course, a plumb-bob should also be used to ensure that each course is vertically aligned/straight (c).

a.

b.

c.

F.

Fill in the vertical (side) interlocks of each block with mortar using a trowel and smooth with a wooden float on all sides (both front and back). The mortar to fill in vertical interlocks should use more water so that it can more easily be put into the interlocks. 8

5

Wall Construction

G.

From the second course onwards only 5mm of mortar should be used in the horizontal interlocks. Make sure that each course staggers with the one below it to form a ‘T’ joint.

5mm

H.

When each course is finished, check that all sides of each block have been mortared and smoothed.

I. Repeat steps D-H until the appropriate amount of courses have been built.

Allow 1 day for wall to dry.

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6

Inside Plastering & Waterproofing

Before you begin plastering, you must first fit the tap and washout pipes. Once these are in place, plastering may begin.

A.

Starting from the inside of the tank, chisel out two holes for the tap and washout pipe. The tap should be located 3 inches above the base and the washout pipe should be located at the same level as the base. The 2 pipes should be located about 6 inches apart.

3 inches

6 inches Stone

B. Fix tap and washout pipe in place using stones to secure it in the holes.

Stone

C. Plaster should be made with a ratio of 1:4:1

(cement: sand: waterproof cement [1kg bag]). Begin plastering the inside walls of the tank using a trowel.

D.

Level the plaster using a bar line. Smooth the plaster by running a wooden float over the plaster in a circular direction. It may be helpful to apply water to the wooden float. 10

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Inside Plastering & Waterproofing

E.

When walls are finished, plaster the floor of the tank. The plaster should create a virango. This means that the sides of the base will taper down to the centre allowing sediment to collect on the bottom of the tank. The sides of the base should begin at the level of the tap opening.

Tap 3 Inches

Virango Washout

Virango

F.

Metal Float

Once completed plastering the inside of the tank, a layer or waterproof cement should be applied using a metal float to smooth the waterproof cement to the surface and the base. The ratio for waterproof cement mixture is 1:21/2:1 (1kg bag of waterproof cement: 2 1/2 heaped wheelbarrows of sand: 1 50 kg bag of cement).

Notes:

1. Always place a wooden beam on top of the tank to facilitate exit after applying waterproof cement. Carefully get out of the tank without damaging the fresh plaster 2. The day after applying waterproof cement, it is important to poor water into the tank to cover the bottom of the tank. This will make sure that the plaster cures properly and does not crack. Temporarily cover the tank top with a polythene sheet or with iron sheets.

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7

Fitting wire mesh & Outside Plastering

A wire mesh that equals the circumference of the tank will be tightened around the outside of the tank using binding wire. Plaster will then be applied to encase the wire mesh and create a smooth finish on the outside of the tank.

A. To join the wire mesh together to form 1 single piece of wire mesh:

1. Use pliers to twist the wires on one end of the mesh sheet to a 180° angle. 2. Hook 2 wire mesh together and hammer the end of one sheet around the other .

B. Cut out the tap vent area (1.5 ft. x .5 ft.) on the wire mesh to line up with where the tap will be on tank. Wire cutters can be used to do this.

1.5 ft x .5 ft

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Fitting wire mesh & Outside Plastering

C. Fix the wire mesh around the

tank placing the tap vent cut out area at the tap location. Fix the 2 sides of wire mesh together by weaving binding wire through each side. Use pliers and pull in the ropes to tighten binding wire if needed.

D.

Once the wire mesh is secure, apply a layer of plaster to the outside of the tank. Once finished, apply a second layer to fully cover the wiremesh.

E.

To level plaster use a bar line. To smoothen, run a wooden float over plaster in a circular direction. It may be helpful to apply water to the wooden float.

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8

Roofing the Tank

The steps of roofing start with putting in place an overflow pipe. After this has been secured, roofing may begin.

A. To fix the overflow pipe, pick an area where water will be able to drain away

properly from the tank. Chisel two inches into the top course of blocks to fit the overflow into. Secure the overflow pipe in chiselled area with mortar. The length of the overflow pipe should protrude at least 6 inches from the side of the wall. The overflow pipe should also have a diameter that is equal to or larger than the pipe carrying in water from the gutters. We recommend a 4 inch PVC pipes. > OR = Diameter of inflowing gutter pipe

2 Inches 6 Inches

Wooden Beam

B.

The roof is secured with 4”x 2” wooden beams using 5” nails. Place a wooden beam at the centre of the tank and another one every 23 feet outwards. Each wooden beam should be long enough to reach from the edge of one side to the other side. Do not nail the beams in place yet.

2ft-3ft

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Roofing the Tank

C.

The roof needs to have a gentle slope towards one side so water does not collect on the roof surface. To create this, the first wooden beam where the top of the slope will start should rest vertically onto the surface of the top course of bricks. The second beam will be placed vertically, however, the area where is rests on the bricks should be chiselled down 1 inch. The next wooden beam and subsequent wooden beams will rest horizontally on the tank. In turn, all the beams will create a gentle slope when iron sheets are laid onto them. Horizontal Vertical

Chiselled 1 Inch

D. Once positioning of the beams has been

figured out and any necessary chiselling made, nail the beams into the bricks using four 5” nails.

E.

Fill area between the last course and top of each beam/roof height with mortar, spare wood, and any extra blocks.

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Roofing the Tank

F. Fix iron sheets onto the wood

beams with roofing nails by laying the iron sheets perpendicular to the wood beams and overlapping two ridges over the other for proper 1 Foot interconnection. There should be a 1 foot overhang around the tank.

G. Using a metal cutter, cut

1 Foot

off the excess iron sheeting shaping it around the tank. Allow for an overhang of 1 foot around the whole tank . You can use either metal cutters or a panga to cut the iron sheets.

H. Apply plaster over the blocks/ wooden pieces that fill in the space between the last course and the roof. This will connect the walls to the roof area. Smooth over with a wooden float.

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9

Veranda & Pit-Tap Area

A. Level the area around the tank

the width of 1 block. Place a row of blocks around base of tank to form a veranda. Plaster that blocks and smooth the area. Apply a layer of waterproof cement to the verandah.

B.

Dig out a pit below the tap that is large enough to place a jerry can and remove it. Line with blocks or block chips.

C.

Plaster the dug out area and the lined blocks. Smooth with the rest of the veranda. Apply a layer of waterproof cement to the dug out area.

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10

Tank Maintenance*

Regular inspection, cleaning, maintenance and occasional repairs of all tank components ensure that the maximum amount of good quality rainwater is collected. The following tasks should be done at least once a year to keep the catchment wellmaintained: 1. Keep the house and tank roof in good condition. Repair any holes in the roofing material to prevent leaking. Seal any nail holes that are leaking. 2. Clean the house roof between rainfalls. Debris and excrement from birds and small animals can be removed by sweeping the roof often. 3. Keep the gutters in good condition. Be sure that they are firmly fixed to the roof and that they are joined to prevent spilling. Repair any holes in the gutter to prevent leaking. Check bamboo or wood gutters once a year for rotting. Replace them if there is any sign of rot. 4. Periodically remove leaves and other debris from the gutters to avoid clogging and water overflow. 5. Wash out the tank using the washout pipe 1 time a year to clean out soil and dust that has settled on the floor of the tank. 6. Regularly inspect taps to ensure that they are not broken or leaking. A leaking tap can quickly lose thousands of litres and drain a surface tank. Any leaks should be fixed immediately. 7. Regularly check tanks for any cracks. Any leaks should be repaired immediately. * Information taken from the Centre for Affordable Water and Sanitation Technology (CAWST), Roof Catchment Systems: 2007.

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Determining Tank Capacity & Equations

Tank Capacity: To determine tank capacity the formula for Volume is used. The volume for formula multiplies the radius squared by pie and height = Volume= (r*r) * pie * h Where: Volume = litre capacity r = radius (half of diameter) pie = 3.14 h= height

Example: 5,000 L Tank: V= (r*r) * pie * h Where: V= ? D= 2m (r= 1) h= 1.6m V= 12 * 3.14 * 1.6 = 5.024 m3 = 5.024 x 1,000 = 5,024L (approx 5,000L)

Circumference: To determine the cirumference of the tank multiply the diameter by pie = circimference =d * pie Meters to feet conversion: To change from meters to feet divide the number of meters by 0.3048 = meters/0.3048

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Sample Building of Quantities 2,000 Litre water tank Diameter: 1.5m Height: 1.2m # of blocks: 200 • 17 blocks per course • 10 courses of blocks Materials

Quantity

Cement

6 bags

Iron Sheet for top of tank Timber for top of tank Tap and washout Aggregate Sand

Notes Includes for blocks

1.5

G32

1

4x2

1 1.75 tonnes 3 tonnes

Overflow pipe

1

Wire mesh

1.5

Roofing nails 5” nails Waterproof cement Binding Wire

1/2 kg 1/2 kg 1 bag

1’ of PVC pipe with 4” diameter G10

1 kg bag

1/2 kg 20

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Sample Building of Quantities 5,000 Litre water tank: Diameter: 2 meters Height: 1.6 meters # of blocks: 330 • 23 blocks per course • 14 courses of blocks

Materials Cement Iron Sheet for top of tank Timber for top of tank Tap and washout Aggregate Sand

Quantity 10 bags

Overflow pipe

1

Wire mesh

3

Roofing nails 5” nails Waterproof cement Binding Wire

1 kg 1 kg

Notes

3

G32

2

4x2

1 1.75 tonnes 3.5 tonnes

4 bags

1’ of PVC pipe with 4” diameter G10

1 kg bags

1 kg

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Sample Building of Quantities 10,000 Litre water tank: Diameter: 2.5 meters Height: 2 meters # of blocks: 510 • 28 blocks per course • 17 courses of blocks

Materials Cement Iron Sheet for top of tank Timber for top of tank Tap and washout Aggregate Sand

Quantity 17 bags

Overflow pipe

1

Wire mesh

4

Roofing nails 5” nails Waterproof cement Binding Wire

1 kg 1 kg

Notes

3

G32

3

4x2

1 3.5 tonnes 7 tonnes

5 bags

1’ of PVC pipe with 4” diameter G10

1 kg bags

1 kg 22

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