The practice of rainwater harvesting is 4,000 years old. In the absence of modern methods for extracting and distributing water to each household, our ancestors had to rely on rainwater harvesting methods, using natural water sources and rain. In broad categories, there are two versions- Land-based and Roof-based rainwater harvesting. The latter is more popular as the collected water can be made available for potable use.
In most of the developing countries, rainwater harvesting has become essential, owing to the sequential and spatial variability of rainfall. In India, the annual and regional distribution of rainfall differs significantly. The complete reliance on groundwater is not an option due to its restrictive availability. Plus, water supply in household and office buildings is chargeable. These factors have made rainwater harvesting a necessary solution. It can help in saving up to 50% of the total household consumption.
The practice of harvesting rain is simple enough to be followed at individual homes and buildings. A community-level rainwater harvesting is now being practiced in almost every newly built housing society, which save even greater amounts of water for gardening and cleaning purposes. The rooftop rainwater harvesting is practiced if a potable amount of water is intended from RWH systems.
Basics of Rooftop Rainwater Harvesting.
It is the technique which harvests rainwater with three basic elements:
- A collection area, which is a roof of the house or a building. The total surface area and the type of material used in roof construction decide the efficiency in collecting rain and the quality of that collection.
- A conveyance system consists of gutter or pipe which transports the rooftop water into cisterns or other storage vessels. The drainpipes and the roof surfaces must be built up of inert materials like wood, plastic, fiberglass or aluminium. This is important to avoid any adverse effects on the quality of the water.
- Storage facilities include storage tanks or cistern, built using only an inert material. Storage facilities can be made as a part of the building while in some designs, they are built as a separate unit, at some distance away from the main building.
Properties of a safe rooftop, for harvesting
Roof is a primary surface for collecting rain in rooftop RWH method hence it is important that it must be made up of a non-toxic material.
Though it is recommended to avoid painted roof surfaces but if done, use the paints which are lead-free, chromium-free and zinc-free.
Any type of overhanging vegetation must not be present on the roof. This will contaminate the caught water and lead to the blockage of gutters and conduit.
Components of a perfect storage unit
There are few minimum requirements for the storage tanks and then, there are some additional accessories to be fixed, for better storage capability and quality.
Each storage tank must have:
- A secure cover built up of solid material.
- A coarse inlet filter
- A pipe to handle overflow
- A manhole to facilitate cleaning
- A system like a tap or pump, to extract stored water. Be careful to use the system which does not contaminate the water.
- To prevent spilling of water and making puddles near the tank, a soakaway must be used.
Additional accessories may be included, as
- a device which can measure the amount of water in the tank.
- A foul flush mechanism like sediment trap or tipping bucket.
- A lock for the tap to prevent accidental opening and wastage of water.
- A second sub-surface tank which can provide water for alternative use, like for drinking by livestock, etc.
Treating the water stored in the tank
As mentioned earlier, the rooftop RWH system is a fairly simple structure which is easy to implement. The biggest concern is to maintain the quality of a large amount of stored water, which is prone to contamination by bacteria, mosquitoes, or solid wastes.
With all the precautions taken to prevent the contamination of water at the rooftop level, there are still chances that harmful particles can make their way into the storage tank. If the main purpose of the rooftop harvesting is to have a potable water for drinking or cooking, then it must be treated well.
Here are few pieces of advice:
- A long dry spell may lead to the collection of dry leaves, birds dropping or other contaminated particles. The foul flush method must be practiced, wherein the first part of every rainfall is diverted away from the storage tank. The rainwater in the first 10 minutes of high-intensity rainfall is generally diverted as it is considered unfit for storing.
- Boiling and thermal microbial deactivation are the traditional methods of procuring safe drinking water.
- Scrub the inner walls and floors of the storage tanks, periodically. Use a chlorine solution followed by a thorough rinsing.
- Treat the water sodium hypochlorite, NaDCC (sodium Dihloroisocyanurate) dosing, chlorine disinfection combined with safe water storage.
- A non-conventional chlorination device can be made. It has a rubber tube, plywood, a 1.2 m piece of PVC tubing, and a hose clip which inserts chlorine tablets in the water.
- Silver impregnated ceramic filters can be used to keep bacteria and virus from getting developed in the water.
- For community catchments, there is a requirement for an extra protection by fencing the paved catchment, to restrict the entry of livestock such as cows, donkeys, goats, pigs, etc.
- Maintenance for the large cracks should be done as soon as possible. These cracks may get developed as a result of soil movement, earthquake or exposure to elements.
Use of Harvested Rainwater
The use of rainwater harvesting system has direct positive implications over the environment. Along with lowering the energy consumption of the premises, the water harvested during long rainy reason can help in intermittent use during dry season.
The rooftop harvesting can also be used to store water in lesser quantity in small containers, for occasional use when there are few “no-rain” days, in otherwise uniform monsoon season.
To lower the consumption of household water usage, harvested water can be used partially for drinking and cooking only, while alternative water supply remains reserved for other domestic chores like cleaning, bathing, laundry, etc.
In the higher rainfall season, the harvested water can fulfil the demand of water for all types of household needs, for the whole year.
Chaitanya & their rooftop rainwater harvesting solutions
The requirement and catchment site differ for every household, hence each needs personalized survey and analysis for installing the RWH system. The superior quality rooftop drainage gutters and filters at Chaitanya, can help in procuring the best quality water, harvested from the system.
Talk to our experts and know how it is worth to invest in rooftop RWH systems.