RAPID PLAS - Life at Its Best    ---True Blue Hot Deals---

Poly water tank on its way? Be prepared

rainwater tank installation

You’ve taken the plunge and bought a water tank so you’re ready for rain. What needs to happen first? 

Buying a poly water tank to give you a measure of water safety is just the first step. But before it’s delivered to your property, you need to prepare for its arrival. 

How? It isn’t that hard if you follow our easy step-by-step guide. 

Step 1: Choose the site where your poly tank will go 

You need to keep in mind that 1,000 litres of water weighs 1 tonne so the ground needs to be stable. It also needs to be close to a structure like a shed or garage if the poly tank is for your home. 

Step 2: Prepare the base for your water tank 

  • For circular tanks: Tie a ball of string to a tent peg or stick and place the peg in the centre of where you want your tank. Measure off the radius of the base of your tank (we can give you measurements) then add at least 600 mm. Using the string line, draw a circle. 

  • Level the marked area, making sure you clear any rocks, stones or sharp objects. Remember the weight of all that water? Over time, your tank will settle and even small stones could puncture the base of your tank. 

  • When you’ve finished levelling and clearing the base, check your work with a level. 

For slimline tanks, the levelling process is the same, and you need a 600 mm clearance, too. 

Step 3: Create your base 


  • Mark a height of 75 mm. (If you can, use some kind of retainer like old railway sleepers or 2 x 4 timber.) 

  • Fill with fine road base gravel or crusher dust (but not sand, as it’s likely to erode through any rain flowing down the side of your tank).  

  • Spread evenly then check the base is level in all directions. 

  • Water lightly so gravel settles. 

  • Use a compactor or roller to compact the base. 

  • Double-check that the site is level and you have a margin of 600 mm 


Follow the same steps above to level your site and remove sharp stones. If you’re doing the concreting yourself, note that we recommend that you use some kind of mesh to maintain the integrity of the base. Generally we recommend that you engage a concreter.  

Remember the weight: You might need to calculate the concrete slab thickness you need for the size of your tank. 

Need more info on preparing for your rainwater tank? 

Give us a call. It’s what we do so we’re always happy to help. Call us on (02) 6765 0700 and talk to one of our helpful team.