According to the studies, a typical family in the US consumes an average of 5000 to 10000 gallons of water per month. The average monthly bill ranges from $25 to $70 per month across various locations in the States. Some areas levy a uniform rate regardless of water consumed, while other areas may have block rates in which the rates rise as usage increases or the other way around. Water is bound to become more expensive. In this scenario, it is best to consider rainwater harvesting to offset these expenses. If not for drinking purposes, you can use harvested rainwater for watering the lawn, gardens and can also be used for other domestic purposes. Harvested rainwater could last for a couple of months or even more depending on tank capacity.
Water tanks for storage
Harvested rainwater can be stored in water tanks made of polyethylene, steel, laminated steel or in concrete tanks underground. The water tank used for rain water harvesting is preferably kept separated from the main water supply tank if the house has one. In this case, the tank would require accessories like a water pump, appropriate filters, a feed pipe from the roof and an overflow pipeline.
Tank size depends on amount of water collection area and local average rainfall figures. If the local rainfall is around 20 inches per year and the area of the roof is about 2000 square feet then the average water collected would be about 10000 gallons.
Types of water tanks
There are plenty of choices in the types of water tanks to store harvested rainwater.
- The simplest and perhaps the most affordable is a roto moulded polythene tank with UV protection. The tank can be put on a platform of concrete with some cushioning of sand to even out the pressure.
- Galvanized tanks are also a good option. But one must keep in mind that metal tanks are prone to galvanic corrosion and rusting, especially around the welded points.
- Plain steel tanks made of 1/8 inch thick mild steel or thicker can be used. However, the plain steel tanks, though cheaper, may rust and develop leaks over time.
- Polymer or rubber lined steel tanks are better but, if there is even a pinhole defect in the inner lining, the steel tank could rust and develop leaks.
- An option to save space is to dig the ground and lay out a concrete tank which should usually last for lifetime or more. But this might entail some more expense and effort. But is more reliable than the other methods.
- Round polymer water tanks with corrugated side walls are popular and priced affordably. If made with UV resistant polymers, these tanks have a long life.
- Another option is to use polymer material slimline water tanks that can be erected against one blind wall or can be placed inside the garage. Slimline tanks are also available in polymer coated galvanized steel. This type of tank should have a service life of 20 years. Keep in mind that polymer tanks can be installed above the ground and even underground. But it is not recommended that steel water tanks be put underground because it is more prone to corrosion.
Saving on monthly water bills is just one aspect of rain water harvesting. There are other benefits too. One is that you contribute to conservation of the environment by reducing load on public water distribution system. Stored rainwater can also come into use when such public distribution systems develop a fault. For off the grid housing or remote areas, rainwater stored in tanks is a veritable boon and could meet a major part of their requirements.