Converting Rainwater into Potable Drinking Water – Methods and Benefits

The drinking water demand of our earth’s population is generally fulfilled by two sources – groundwater and surface water (river, streams, waterfalls). However, rainfall is a major source of supply for above-mentioned sources. So, isn’t it a great idea to directly use the rainwater for drinking purpose? And moreover, rainwater is considered the purest form of water.

By the purest form of water, it is meant that rainwater has a low mineral composition and acidic content. But that does not mean it is safe to directly drink the rainwater. Even though its natural composition is neutral, the rainwater drops do pick up pollutants and dirt from the atmosphere, especially in the areas of high chemical industries and nuclear explosions. There are more reasons that support the need for purifying rainwater before using it as a potable water.

Why there is a need to purify rainwater before drinking

The rainwater may contain one or more of the following contaminations, that made it unsafe from drinking without running it through purification methods:

  • Firstly, the raindrops while reaching the earth’s surface, collect the dirt, harmful chemicals, smoke, etc. present in the atmosphere.
  • On reaching the earth surface, it gets mixed with animal faeces, algae, sand, twigs, dead insects, etc.
  • The contaminated water becomes the breeding ground for E.coli, microorganisms and other life-threating bacteria.
  • From certain old types of roof, the rainwater can have dissolved asbestos which is a fibrous silica compound and is a carcinogen (a substance that may become a leading cause of cancer).

Filtration methods for harvested rainwater

The best way to use rainwater for drinking purpose is to design the rainwater harvesting systems at home and run this collected water through a filtration system.

There are many methods for rainwater filtration and purification. The choice would depend upon

  • The amount of rainwater available for purification
  • Your expenses budget
  • The available resources in your part of country or state.

Here are few natural and equipment-based filtration methods for converting rainwater into potable drinking water reserves:

  1. Installing flush devices, filters, and screens

The water received on the catchment areas must be passed through first flush devices to block the tangible and large-sized pollutants like leaves, twigs, birds’ excrement and sand etc., before the rainwater enters the conveyance system (distribution pipes).  Along with first flush devices, the gutter screens can also be installed at the edges of the catchment area. This will reduce the blockage in the conveyance system and thus reducing their maintenance cost.

Within the water storage tanks, the filters are needed to keep the pollutants settled down at the bottom of the tank. The filtration systems may include screen filters, paper filters and carbon or charcoal filters.

Filters are measured in microns. One micron is about 1/25,000th of an inch.

  1. Disinfectant Methods

Filters are effective at separating visibly large pollutants from the collected rainwater, but they will not eliminate all substances. For quality drinking water, filtration must be accompanied by disinfectant methods, which lead to the removal of dissolved micro-pollutants.

 Chlorine treatment

Chlorine is being used as the major method of disinfection in most of the public water systems. For this purpose, 2.3 fluid ounces of household bleach must be added per 1,000 gallons of water. However, the dosage rate will vary depending on the quantity of water to be treated, pH and the temperature.

Chlorine is effective in eliminating waterborne diseases such as cholera, typhoid, dysentery, and hepatitis. However, care must be taken as chlorine is highly reactive and can combine with various other naturally occurring organic materials, creating harmful combinations that can be hazardous to health.

Using Ultra Violet (UV) lights

Passing water through ultraviolet lights can disrupt the microorganism cell’s genetic makeup, to make them unable to reproduce. Before treating water under UV lights, it must be passed through the filtration system.

For effective disinfection, replace the bulbs after 9,000 hours, or about every 12 months. The UV units are effective on particulates not more than 50 microns and the water must not contain tannins, sulfur or sulfur-related bacteria. This can be known by testing the water quality in a lab.

Using membrane filtration

Another alternative filtration method is membrane filtration. There are pressure-driven membrane technologies such as microfiltration, ultrafiltration, nanofiltration and reverse osmosis.

Amongst each other, Reverse Osmosis (RO) is the most widely used membrane technology. They are capable of removing particles as fine as .001 microns like radium, natural organics, pesticides, cysts, bacteria, and viruses.

The RO units, however, results in water wastage, as, major amount of the water is flushed out in the process of removing contamination. Even though, the RO systems are compact and most suitable for household use.


This is the simplest method of water purification. The water is boiled which can evaporate the impurities and the condensed purified water is collected in the containers. About 5-10% of the water is lost due to evaporation.

The distillation process is capable of removing almost all substances from the water except for volatile organic chemicals (VOCs). Using carbon filters in a distillation system can help in removing VOCs.

Benefits of using harvested rainwater for drinking

Though it requires a proper arrangement for using rainwater for drinking purposes, it is worth doing.

  • It reduces pressure on naturally occurring water sources (groundwater and water streams) which takes a lot of time for replenishment.
  • The purified rainwater contains alkaline pH, which has detoxifying effects to promote a healthy digestion.
  • The mineral content of rainwater is low which is a good condition to reduce headaches, gastritis and damage to body organs.
  • It promotes healthy skin and hair due to its alkaline pH. It maintains the skin’s natural moisture and promote healthy hair growth.

With little planning and investment, we can harvest the great potential of rainwater and help in maintaining our health, as well as that of our environment.

Rainwater gutter filters and screens at Chaitanya

Chaitanya products are the providers of the most modern and award-winning rainwater harvesting products and services.

There, one can find Vee wire filter screens which are efficient and non-clogging rainwater screens, rainwater drainage gutters for specific use in industries and similar other materials for home and agriculture use of harvested rainwater. There is no compromise at Chaitanya when it comes to quality products and services.

Leave a Reply

Your email address will not be published. Required fields are marked *