DIY Ferrocement Water Tank: A Step-by-Step Guide

Access to clean and reliable water storage is crucial, especially in areas facing water scarcity or unreliable infrastructure. While commercial water tanks can be expensive, building your own ferrocement tank is a cost-effective and durable alternative. Ferrocement, a composite material made of cement, sand, and layers of wire mesh, offers exceptional strength and longevity. This comprehensive guide will walk you through the process of constructing a ferrocement water tank, providing detailed steps and essential considerations.

What is Ferrocement?

Ferrocement is a type of reinforced concrete characterized by a high ratio of surface reinforcement. It consists of closely spaced layers of wire mesh embedded in a cement mortar matrix. This unique composition results in a material with high tensile strength, impact resistance, and crack resistance. Ferrocement structures are relatively lightweight compared to traditional concrete and can be molded into various shapes, making them ideal for water tanks, boats, and other construction projects.

Advantages of Ferrocement Water Tanks

• Cost-Effective: Ferrocement utilizes readily available and relatively inexpensive materials.
• Durability: Ferrocement tanks are highly resistant to cracking, impact, and weathering, ensuring long-term water storage.
• Customizable: The design and size of the tank can be adapted to specific needs and site conditions.
• Easy to Repair: Minor cracks or damages can be easily repaired with cement mortar.
• Potable Water Safe: When properly constructed with suitable materials, ferrocement tanks provide safe storage for potable water.

Planning Your Ferrocement Water Tank

Before embarking on the construction process, careful planning is essential. Consider the following factors:

• Water Storage Capacity: Determine the amount of water you need to store based on your daily consumption and the duration of dry periods.
• Tank Location: Choose a suitable location that is easily accessible, level, and provides adequate support for the tank. Consider proximity to your water source and drainage.
• Tank Shape and Size: Common shapes for ferrocement tanks include cylindrical and rectangular. Select a shape and size that optimizes space utilization and structural integrity. A circular tank is structurally more sound.
• Foundation: A strong and stable foundation is crucial to prevent settling and cracking.
• Materials: Source high-quality cement, sand, and wire mesh to ensure the durability of your tank. Use potable water safe sealant where required.
• Tools and Equipment: Gather the necessary tools and equipment, including shovels, wheelbarrows, mixing tools, wire cutters, pliers, and safety gear.

Materials Required

Here is a list of the materials you’ll need for constructing your ferrocement water tank:

• Cement: Ordinary Portland Cement (OPC) is commonly used. The amount depends on the tank size.
• Sand: Use clean, well-graded sand, free from organic matter.
• Water: Use clean, potable water for mixing the mortar.
• Wire Mesh: Galvanized iron (GI) wire mesh is recommended for its corrosion resistance. Chicken wire or chain-link fencing can be used. Several layers are required.
• Reinforcing Bars (Rebar): Steel reinforcing bars provide additional strength, especially for the base and larger tanks.
• Binding Wire: Used to tie the wire mesh layers together.
• Formwork Material (Optional): Plywood, metal sheets, or other materials can be used to create a temporary mold for shaping the tank.
• Waterproofing Compound (Optional): A waterproofing admixture can be added to the mortar mix to enhance water resistance.
• Curing Compound (Optional): Helps retain moisture during the curing process.
• Inlet/Outlet Fittings: Purchase appropriate fittings for water inflow and outflow.
• Drain Valve: A drain valve at the bottom allows for easy cleaning.

Tools and Equipment

Gather the following tools and equipment before starting construction:

• Shovels and Wheelbarrows: For mixing and transporting materials.
• Mixing Trowel or Concrete Mixer: For thoroughly mixing the mortar. A concrete mixer is highly recommended for larger tanks.
• Wire Cutters and Pliers: For cutting and shaping the wire mesh.
• Measuring Tape and Level: For accurate measurements and ensuring a level foundation.
• Hammer and Nails (if using wooden formwork): For constructing the formwork.
• Float or Trowel: For smoothing the mortar surface.
• Safety Glasses and Gloves: For protecting your eyes and hands.
• Dust Mask: To avoid inhaling cement dust.
• Ladder or Scaffolding (if required): For reaching higher areas of the tank.
• Personal Protective Equipment (PPE): Safety shoes, helmets.

Step-by-Step Construction Process

Follow these steps to build your ferrocement water tank:

Step 1: Site Preparation and Foundation

1. Clear the Site: Remove any vegetation, debris, and topsoil from the tank location.
2. Level the Ground: Ensure the ground is level and compact.
3. Foundation Design: The foundation should be designed to support the weight of the filled tank. For smaller tanks (up to 5,000 liters), a reinforced concrete slab of 4-6 inches thickness is usually sufficient. For larger tanks, consult with a structural engineer.
4. Pour the Foundation: Mix concrete (cement, sand, and gravel) and pour it into the prepared area. Use a level to ensure a flat surface.
5. Cure the Foundation: Keep the concrete moist for at least 7 days to allow it to cure properly. Cover it with wet burlap or plastic sheeting and spray with water regularly.

Step 2: Building the Frame (Optional but Recommended)

While not strictly necessary, building a frame simplifies the process and ensures a uniform shape, especially for cylindrical tanks. This frame acts as the supporting structure onto which the mesh will be attached.

1. Design the Frame: Determine the dimensions of your tank and design a frame accordingly. For a cylindrical tank, you’ll need circular top and bottom rings and vertical supports.
2. Cut the Materials: Cut the wood or metal (if using) to the required lengths.
3. Assemble the Frame: Assemble the frame, ensuring it is sturdy and level. Use screws or welds to join the components.
4. Secure the Frame: Place the frame on the cured foundation and secure it to prevent movement during the mesh application.

Step 3: Creating the Wire Mesh Cage

1. Cut the Wire Mesh: Cut the wire mesh into appropriate sizes to cover the entire surface area of the tank (or frame, if used). Overlap the edges of the mesh sections by at least 4-6 inches.
2. Form the Cage: Wrap the wire mesh around the frame (or the area where the tank will be built). Overlap the edges generously. Use binding wire to tie the mesh layers together at regular intervals (every 4-6 inches).
3. Layer the Mesh: Apply multiple layers of wire mesh, typically 4-6 layers for smaller tanks and more for larger tanks. Each layer should be securely tied to the previous one with binding wire. The number of layers depends on the tank’s size and desired strength. Aim for a dense mesh reinforcement. Stagger the seams of the wire mesh layers for increased strength.
4. Rebar Reinforcement (for larger tanks): For larger tanks, consider adding vertical and horizontal rebar reinforcement. Tie the rebar to the wire mesh cage using binding wire. This provides additional structural support.
5. Inspect the Cage: Once the wire mesh cage is complete, carefully inspect it to ensure that all layers are securely tied together and that there are no loose ends or sharp edges.

Step 4: Applying the Mortar

1. Prepare the Mortar Mix: Mix cement and sand in a ratio of 1:2 or 1:3 (cement:sand) with enough water to create a workable mortar consistency. The mortar should be plastic enough to be pressed through the mesh but stiff enough to stay in place. Consider adding a waterproofing admixture to the mortar mix to enhance water resistance.
2. Apply the First Coat: Apply a thin layer of mortar to the wire mesh cage, pressing it firmly into the mesh openings. Ensure that the mesh is completely covered and that there are no voids or air pockets. This is the most crucial layer for structural integrity. Work from the bottom up to prevent the mortar from sagging.
3. Curing the First Coat: Mist the first coat with water and cover it with plastic for 24 hours to promote proper curing.
4. Apply the Second Coat: After the first coat has cured for 24 hours, apply a second layer of mortar, again pressing it firmly into the mesh. Build up the thickness of the mortar layer gradually, ensuring a smooth and even surface.
5. Curing the Second Coat: Cure the second coat for another 24 hours as you did with the first.
6. Apply Additional Coats (if needed): For larger tanks, you may need to apply additional coats of mortar to achieve the desired thickness and strength. Cure each coat for 24 hours before applying the next. The total mortar thickness should typically be between 1-2 inches.
7. Finishing the Surface: Use a float or trowel to smooth the final mortar surface. Ensure there are no sharp edges or rough spots. A smooth surface will help prevent water leakage and make the tank easier to clean.

Step 5: Curing the Tank

Proper curing is essential for the strength and durability of the ferrocement tank. Curing involves keeping the mortar moist for an extended period to allow the cement to hydrate properly.

1. Keep the Tank Moist: Keep the tank moist for at least 7-14 days after applying the final coat of mortar. This can be done by regularly spraying the tank with water, covering it with wet burlap or plastic sheeting, or using a curing compound.
2. Avoid Direct Sunlight: Protect the tank from direct sunlight during the curing process to prevent the mortar from drying out too quickly.
3. Consistent Moisture: Ensure that the mortar remains consistently moist throughout the curing period. This is crucial for achieving maximum strength and minimizing cracking.

Step 6: Installing Fittings and Fixtures

1. Inlet and Outlet Pipes: Install the inlet and outlet pipes at the desired locations. Ensure that the pipes are properly sealed to prevent leakage. Use a waterproof sealant around the pipe connections.
2. Drain Valve: Install a drain valve at the bottom of the tank to allow for easy cleaning and draining.
3. Overflow Pipe: Install an overflow pipe to prevent the tank from overfilling.
4. Access Hatch: Provide an access hatch on the top for cleaning and inspection. The access hatch should be tightly sealed to prevent contamination of the water.

Step 7: Testing and Sealing

1. Initial Leak Test: After the curing period is complete, fill the tank with water and check for leaks. Mark any leaks that you find.
2. Repair Leaks: Drain the tank and repair any leaks with cement mortar or a waterproof sealant. Allow the repairs to cure properly.
3. Final Leak Test: Refill the tank and check for leaks again. Repeat the repair process until the tank is completely leak-free.
4. Internal Sealing (Optional): Consider applying a food-grade epoxy coating or other potable water safe sealant to the interior of the tank to further enhance water resistance and prevent contamination.

Step 8: Protecting the Tank

1. External Coating (Optional): Apply a protective coating to the exterior of the tank to protect it from weathering and UV damage. This can be a paint or sealant.
2. Shading: Provide shade for the tank to reduce water evaporation and keep the water cooler. This can be done by building a roof over the tank or planting trees nearby.
3. Fencing (Optional): Consider fencing the tank to prevent animals or children from accessing it.

Important Considerations

• Water Quality: Ensure that the water source is clean and free from contaminants. Consider installing a water filter to remove sediment and bacteria.
• Regular Cleaning: Clean the tank regularly to prevent the build-up of sediment and algae. Drain the tank and scrub the interior surfaces with a brush and water.
• Maintenance: Inspect the tank regularly for cracks or leaks. Repair any damage promptly to prevent further deterioration.
• Local Regulations: Check with your local authorities for any building permits or regulations related to water tank construction.
• Professional Advice: If you are unsure about any aspect of the construction process, consult with a structural engineer or experienced builder.

Troubleshooting Common Problems

• Cracking: Cracking can occur due to improper curing, excessive loading, or ground movement. Repair cracks with cement mortar or a waterproof sealant.
• Leaks: Leaks can occur due to poor workmanship, inadequate sealing, or damage to the mortar. Repair leaks promptly to prevent water loss and potential structural damage.
• Algae Growth: Algae growth can occur in tanks that are exposed to sunlight. Prevent algae growth by providing shade for the tank and cleaning it regularly.
• Contamination: Contamination can occur if the water source is not clean or if the tank is not properly sealed. Ensure that the water source is clean and that the tank is properly sealed to prevent contamination.

Conclusion

Building a ferrocement water tank is a rewarding project that can provide a reliable and cost-effective solution for water storage. By following these detailed steps and considering the important factors outlined in this guide, you can construct a durable and long-lasting tank that will serve your needs for years to come. Remember to prioritize safety, use high-quality materials, and seek professional advice when needed. Enjoy the satisfaction of creating your own water storage solution!