Build a Rainwater Catchment Tank from Recycled Plastic Bottles

Updated at: 17/05/2025

Water scarcity is a growing global concern, impacting communities and ecosystems alike. While large-scale solutions are crucial, individual actions can make a significant difference. One surprisingly effective and sustainable method of water conservation is rainwater harvesting, and it's more accessible than you might think. This simple yet impactful project utilizes readily available materials to create a functional rainwater catchment system, significantly reducing reliance on municipal water supplies. By repurposing readily available plastic bottles, you can contribute to a greener future while simultaneously addressing personal water needs.

This guide provides a detailed, step-by-step process for building your own rainwater catchment tank entirely from recycled plastic bottles. We'll cover everything from selecting appropriate bottles and preparing the construction site to assembling the tank and ensuring its longevity. Let's get started and learn how to turn discarded plastic into a valuable resource, one drop at a time.

Preparation and Safety Guidelines

Tools Needed
  • Recycled plastic bottles
  • River sand
  • Cement
  • Reclaimed bricks and rocks
  • Wiring mesh or sisal
  • Waterproof cement
  • Lime
  • Level
Safety Guidelines
  • Ensure all bottles are thoroughly cleaned and free of any harmful chemicals before use. Residual chemicals can contaminate collected rainwater.
  • Use strong and reliable methods to connect the bottles to prevent leaks and ensure structural integrity. A poorly constructed system can collapse under the weight of water.
  • Position the catchment system to avoid potential contamination sources such as animal droppings, pesticides, or overhanging branches.

Step-by-Step Instructions

  1. Gather Materials

    • Collect similar-sized plastic bottles.
    • Sift river sand to remove silt, rocks, and sticks.
    Sift river sand to remove silt, rocks, and sticks.Sift river sand to remove silt, rocks, and sticks.
    Gather Materials

  2. Plan and Prepare the Site

    • Choose a location and lay out the tank dimensions.
    Choose a location and lay out the tank dimensions.
    Plan and Prepare the Site

  3. Construct the Foundation

    • Build the foundation using reclaimed bricks and rocks, and a 5:1 ratio of river sand to cement.
    Build the foundation using reclaimed bricks and rocks, and a 5:1 ratio of river sand to cement.
    Construct the Foundation

  4. Prepare the Bottles

    • Fill the bottles with dirt or rubbish to strengthen them.
    Fill the bottles with dirt or rubbish to strengthen them.
    Prepare the Bottles

  5. Build the Tank Structure

    • Build the tank using a 10:1 ratio of river sand to cement, maintaining a constant radius and level rows.
    • Reinforce the bottle structure with wiring mesh or sisal in a diamond pattern.
    Reinforce the bottle structure with wiring mesh or sisal in a diamond pattern.Reinforce the bottle structure with wiring mesh or sisal in a diamond pattern.
    Build the Tank Structure

  6. Apply Waterproof Plaster

    • Apply a 1cm thick plaster layer (inside and outside) using a 5:1 sand-to-cement ratio, waterproof cement, and lime.
    Apply a 1cm thick plaster layer (inside and outside) using a 5:1 sand-to-cement ratio, waterproof cement, and lime.
    Apply Waterproof Plaster

Read more: DIY Plastic Gallon Candy Basket: Upcycled & Adorable!

Tips

  • Ensure the foundation is level.
  • Consider spigot placement, silt removal, and distance from buildings to prevent leakage.

Common Mistakes to Avoid

1. Insufficient Bottle Sealing

Reason: Poorly sealed or improperly connected bottles will lead to leaks, reducing water collection efficiency and potentially contaminating the stored water.
Solution: Use strong adhesive sealant on all bottle connections and ensure a tight fit between bottles and the connecting parts.

2. Inadequate Filtration System

Reason: Failing to include a proper filtration system exposes collected water to debris, insects, and potential contaminants.
Solution: Add a layer of gravel, sand, and activated charcoal for filtration at the bottom of the tank before adding water.

FAQs

How much water can I realistically collect with a recycled bottle rainwater tank?
The amount of water collected depends on the size and number of bottles used, the size of your roof catchment area, and the amount of rainfall in your region. A small system might collect enough for watering plants, while a larger system could potentially supplement toilet flushing or laundry needs. Don't expect to replace your main water supply.
What type of plastic bottles are best for this project?
Strong, durable plastic bottles are ideal. Look for large, clear bottles made from PET (polyethylene terephthalate) or HDPE (high-density polyethylene) plastic. Avoid bottles that are cracked, damaged, or have been exposed to harsh chemicals.