How to Build a Water Storage Tank

cement waiting to be mixed by a shovel in wheelbarrow
What You'll Need
Concrete mix
Concrete-form release oil
Power drill
Circular saw
Constant water supply
PVC pipe, 1-inch diameter
Tape measure
Cement sealant

Most modern water-storage tanks for individual homeowners are made of plastic and can be expensive to purchase and ship. For those looking for some savings on a tank, or if you don’t have the money to pay full price, you can build a concrete water-storage tank. These do-it-yourself tanks are not only cheaper, but also they often last longer than their plastic competition.

Step 1 – Digging and Leveling

You will need a concrete base to set your storage tank on. This should be a little larger than however big you plan on building your actual tank. On average, most cold-water storage-tank pads are about 10-by-10 feet.

Start by digging out and leveling the area for your pad. Make sure you dig at least 1 foot down, if not a full 18 inches.

Step 2 – Building Base Forms

Cut your wood with a circular saw and screw it together so that it is perfectly square and level when flat, making sure it fits inside your hole. Take all proper safety precautions when using this tool, as misuse can be dangerous. Then, make certain that the base stands tall enough to raise a couple inches above ground. Check the level and adjust as needed until it is perfectly level.

Step 3 – Creating Grooves for the Base

Before pouring your base, you will need a framework to create grooves in the base for your walls to sit in. Screw a set of boards together in the shape of a square, with each side 8-inches wide and 2-inches tall. The length of each side should be the length of each wall of your tank. Nail two boards parallel across the top of this that are longer than your base form.

Step 4 – Filling Your Base

Grease up the inside of your forms with form-release oil, so that you can remove the wood after it dries. Fill at least the first 5 inches of the bottom with gravel, and make sure that it is level. This will promote water drainage.

Pour your concrete on top of the gravel, filling to the top. Use a scrap piece of lumber long enough to reach clear across the top of your form to slide across and level the top of your pad.

Step 5 – Greasing Your Groove Framework

Grease up your groove framework you created in step three with form-release oil, and immediately after pouring your base, lay it across the top of your base form. The square boards should be on the underside, spaced evenly from the edges of your base form. After your concrete dries and you remove the framework, you will have four even grooves for your walls to sit in.

Make sure to allow several days for your concrete to dry.

Step 6 – Constructing Wall Forms

Construct your wall forms from lumber and plywood. Make sure that it is designed so that the plywood sits on the inside where you will pour the concrete, with 2x4s around the outside to hold it together. Ensure that around the bottom, your 2x4s are exactly 2-inches up from the bottom of your plywood, and measure your plywood so that it sits just inside the grooves in your base. This will create a lip at the bottom to keep the excess concrete from spilling out.

Building Methods

You can build your wall forms either separately and erect them one at a time, or you can build them so that they are all connected, allowing you to pour your concrete for all four walls at once. The latter method is more difficult, but the end result looks better after you pull the boards away. Make sure to leave the bottom open and that you have a way of greasing up the inside with form-release oil before use.

Step 7 – Pouring Your Walls

Set up your walls and begin pouring your concrete. Make sure that you have enough on hand before starting to fill the entire form. As you pour, tap on the outside of your form to get any air bubbles to rise out.

Seat a Board

After you are done pouring, level it off and seat a 2x4 board into the top to be used later for attaching your roof.

Step 8 – Drilling an Access Hole

While your concrete is wet but thickening, drill a hole into the side of one wall and insert your PVC pipe to allow for water access. Let the concrete continue to set around the pipe.

Step 9 – Sealing And Covering

After it has set for a few days, remove your wall forms. Go over any place where concrete meets concrete that has dried at different times, such as where the walls meet the base, with a cement sealant to waterproof it.

Make sure to seal around the PVC pipe.

Step 10 – Constructing a Roof

Using your 2x4s on top of the walls, construct a roof of your choice. Then, attach your plumbing. To turn your tank into a portable water-storage tank, be sure to allow access around the roof for adding cleaning chemicals.