How to Install a Water Tank

Bunnings has a wide range of water tanks available.

With much of the continent in drought, having a personal supply of rainwater makes perfect sense.

For our full range of water tanks, please visit your nearest Bunnings Warehouse.

The Concrete Slab

We installed a configuration of three modular units, with a total capacity of 3,000 litres, which equates to about three tonnes. So if you were thinking of sitting your water tank directly on the ground or on a pathway, think again! This and most other water storage tanks require a stable level base. The recommendation for this system is a reinforced concrete slab with a minimum thickness of 100mm.

Estimating the Concrete

Concrete is sold and measured in cubic metres (m3). To estimate the amount of concrete you need, just multiply the length by width by depth. We wanted a slab of 3.7 metres long, 0.65 metres wide and 0.1 metres deep. It's a simple sum: 3.7 x 0.65 x 0.1 = 0.24. So we needed 0.24m3 of concrete.

As this was slightly more than the 0.2m3 increments concrete is sold in, we had two options: reduce the thickness of the slab, or mix our own in a barrow or mixer. We chose the latter option and hired a cement mixer from Kennards.

To make concrete, mix four parts of 10mm aggregate with two parts fine sand and one part grey cement. Add water to the mix until a creamy consistency is achieved.


1	The set-out The overall dimension of each module is 1200mm long and 600mm wide. Adding allowance for space in between, and at the front of the tanks, the overall slab size needs to be 3700 x 650mm. Set pegs and stringlines to these dimensions. HINT: Make allowance for the thickness of the timber form.	2	Excavating Remove grass and excavate to a depth of about 100mm. Pay particular attention to the locations of the damp-proof course and weep holes. The top of the slab must finish below these fixtures.	3	Establishing a level To set the height of the formwork, take a level from just below the damp-proof course. A very slight fall (3-5mm) away from the house is ideal. Don’t exceed this amount as it will cause the tanks to lean forward, creating a large gap between the top of the tanks and the wall.


4	Creating the formwork Make sure that the top of the formwork is level and parallel to the existing wall. Make the formwork from 100 x 75mm timber, which will remain straight during the concrete pouring. You could use 100 x 25mm timber for the formwork, but will need extra pegs to keep it straight.	5	The bond breaker Expansion joint material is attached to the brick wall with a few angled blows from a hammer face. The expansion material acts as a bond breaker, allowing the slab to move independently of the wall.	6	Reinforcement mesh Lay F52 mesh on 50mm bar chairs, with a minimum of 50mm cover (clearance from formwork and wall). Secure the overlapping joints with tie wire.


7	Mixing and pouring Add materials to the mixer in the correct proportions. Add a little water first to prevent the contents sticking to the inside of the mixer. Transfer the concrete to a wheelbarrow and pour carefully into place. Take care not to splash concrete over the existing wall.	8	Finishing the slab Screed off the surface of the slab with an aluminium or timber straightedge, using the top edge of the formwork as a guide. Next, use a wooden float in a circular motion to smooth the surface. Allow the surface to dry a little before dragging a soft broom lightly along the surface of the slab. Use an edging tool to clean up.	9	The socket connections Join the tanks together at the base. Attach a rubber coupling to the socket and tighten the hose clamps securely. Wrap thread tape around the thread of the socket then screw the complete assembly to the deeper recess of the tank.


10	Three tanks in one Apply thread tape to the remaining socket and screw it to the adjoining tank (with the shallow recess). Slide the tanks together, ensuring that the rubber coupling slides over the connector, then tighten the hose clamp securely. Repeat this process for the remaining tanks.		11	Assembling the pump Apply thread tape to threads then connect the PVC riser pipe to the pump fitting. Locate the float cable into the slot in the handle and fasten securely with a cable tie. HINT: It’s essential that the float is positioned 80mm up from the base of the pump.		12	The pump controller Attach pump controller to the PVC pipe, using the supplied union fitting. Then tie the pump cable to the PVC riser using cable ties. Double check that all fittings are tight and attached securely.


13	Power connections Connect the controller socket to the pump socket. HINT: This connection is weatherproof but is not submersible and must stay outside the tank. A standard power outlet must be located nearby.		14	Installing the pump Lower the complete assembly into the tank. Fit the elbow to the controller unit using thread seal tape. Then attach the tap hose securely with the hose clamp. HINT: Do not take the weight of the assembly on the electrical cable!		15	The stormwater Use a length of 90mm stormwater pipe to transfer the level of the tank inlet to your existing downpipe. HINT: This pipe must be totally level for the system to work properly.


16	Preparing the downpipe Measure and mark 350mm up from the base of the inlet position, then 555mm down the mark you’ve made. To make the job easier, remove the downpipe before cutting away the marked section with a hacksaw.		17	Attaching the frogmouth filter As the existing downpipe measured 100 x 75mm and was rectangular, we needed to convert it to fit the 90mm-diameter outlet of the filter. We used a 100 x 75mm to 90mm downpipe converter for the job. Complete instructions for the conversion come with the kit.			Watertight tip Thread seal tape fills the gaps between the threads on a socket to form a watertight connection. It’s essential thread tape is applied in the direction of the thread, otherwise the tape unwinds as the connection is tightened. Which way is right? Always hold the fitting in your left hand and apply the tape forward over the thread so it winds away from you.

Materials & Tools Required

Material	Dimensions	No.
Aquagarden Kit PVC Downpipe PVC Bend Downpipe Converter PVC Pipe Saddles Blue Metal Sand Grey Cement F52 Mesh Bar Chairs Tie Wire	3,000L 3,000 x 90mm 90mm x 45 deg. 100 x 75 x 90mm diameter 90mm 1/4 tonne 1/4 tonne 20kg bags 3,000 x 2400mm 50mm Bundle	1 1 2 2 2 5 0.5 50 pack 50 pack

Tool List
Bolt Cutters Broom Hacksaw Hammer Hardwood Pegs Level	Pick PVC Cement Shovel Stringlines Tape Measure Wooden Float

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How to Install a Water Tank

The Concrete Slab

Estimating the Concrete