Rainwater tanks to supplement your mains supply come in a range of sizes, from 200 litres to upwards of 5,000 litres if you’re planning on indoor use as well. How big a tank you need depends on factors like what you’re using it for, how much rain you get on average, and the size of your roof. Tank providers can help you get the right size for your needs.
Water collected from your roof can contain things like dirt and debris, bird and animal droppings, ash and other residues, so it’s generally not suitable for drinking. In an emergency, though, you can drink it if you boil it first or add chlorine – provided your roof doesn’t contain lead-based paint or uncovered lead flashings etc.
Homeowners can install smaller tanks themselves e.g. for the garden and outdoor use however check with the provider to ensure they are suitable for your needs (Source: Wellington City Council). If you’re planning to connect a tank to your indoor plumbing, you’ll need a qualified plumber to install it.
While you typically won’t need a building consent if you’re installing a tank for outdoor use, you will if you’re connecting it to your home. Depending on your particular situation there may be other instances where a building or resource consent is required – check with your local council first.
Smaller tanks for outside use typically rely on gravity and have a tap. Raising the tank onto a stand provides easier access. You’ll also need a pump for indoor use.