Water: rainwater harvesting

One of the easiest way to obtain water when you’re off the water supply network, is to harvest rainwater. In almost every place on Earth you have some precipitation, if not, you probably won’t be able to live there off  the grid. Water harvesting is so easy I don’t know why it isn’t used everywhere. In cities the rainwater has to be collected and discharged somehow, so IMHO it should be stored and used locally, instead of water from the supply network, to conserve that water. Rainwater harvesting is useful not when you plan to live off the grid!

The basics of rainwater harvesting is the following: take the water from the roof (with the rainpipe), store it in some tank and use it when necessary. In colder climates you can also harvest the water from melting snow and ice, you just need to gather all the snow and ice in one place during the winter and collect the water when it melts in spring.

If you need this water to water your plants, you probably won’t need to do anything with it after it’s collected. You simply pump it from the tank and use it. But for some uses this water would need to be cleaned and filtered. Especially if you want to drink it, but probably also when you want to use it for showers, baths, for your swimming pool, for washing mashine and dishwasher. Of course, the effort required to clean the harvested rainwater to the desired level depends on the local conditions. If you live in a heavily polluted area, where you have a lot of dust and sulphur and nitrogen oxides in the air, you may expect this dust to finish in you rainwater tank — along with sulphuric and nitric acid — so called acid rain. The amount of impurities to be removed from the water is larger when you melt the snow — the snow collects a lot of dust during the weeks it lays on the ground.

As I mentioned above, the rainwater harvesting system (DIY or commercial) consists of the following parts:

• something that collects the water from the roof — typically it’s a system of rainpipes,
• first filter that removes all the leaves and dust particles from the water,
• large tank to hold the stored water,
• a regular filter that cleans the water so it won’t harm the pump,
• a pump to increase the pressure of the water, as almost all of the typical household appliances require pressurized water,
• last filter, to make the water potable, if desired.

This is just the first article in a series about rainwater harvesting.