Replacing a leaking plastic water tank may not be necessary, because you can fix it yourself with a fibreglass patch. These patches are simple to apply and go on in a matter of minutes. You will need some basic repair and construction supplies. When repaired properly, a patched plastic water tank can be used just like a brand new one for many years.
Sand down the area where you want to apply the repair patch. The patch should cover the entire hole and some of the surrounding surface.
Cut the fibreglass patch to fit the sanded repair area with scissors. If the damaged area is large, you might not need to trim the patch at all. The fibreglass cloth patch that comes with the kit usually measures 1.8 to 2.4 square metres (6 to 8 square feet).
Place the fibreglass cloth over the hole.
Mix the epoxy hardener with water until you get a spreadable consistency. Use a stick to mix the epoxy. When you lift the stirrer out of the epoxy, it should run thickly off but should leave a film behind on the stirrer.
Apply the epoxy over the entire patch and spread it over the edges onto the plastic tank with a paintbrush.
Let the epoxy cure for at least 20 minutes before filling the tank with water again.
For larger holes, you may need to use more than one patch.
Do not attempt to patch a hole larger than two patches, as the integrity of the tank will be compromised.