How Long Can You Store Rainwater for Drinking

In many areas of the Country, Harvesting Rainwater can be a viable solution to ensuring, water that is needed for cleaning, flowers, and vegetable gardens along with getting your browning lawn through those long water restrictions in the Summer months but also for a viable Potable Water source too. Storing harvested water in a container that is prepared properly can solve some of those problems for a longer holding time. How Long Can You Store Rainwater for Drinking?

  • Rainwater can be stored up to 5 yrs if you prep the drum:
  • Add 2 Cups of 6% Unscented Bleach to a Food Grade High-density Polyethylene Drum
  • Rinse out
  • Use a pre-filter to fill
  • Add an H2O Preserver
  • Seal & date Drum
  • Store off ground in the shade
  • Before Drinking Run H2O through a Gravity Filter using RO & Carbon

Due to Climate Change and Water Scarcity clean-safe  Drinking Water is becoming harder and harder to come by. The sustainable idea that comes to the table, for the most part, can work with just small details that are needed to be worked out. Using Rainwater is will be part of the future of sustainable answers that will be built in the Urban Design

Is Rainwater Safe to Drink


Because Rainwater is a natural result of the earth’s Water Cycle, there has been lots of importance that have been attached to it. It feeds the aquifers, wells, Rivers, and lakes feeding public water systems on the planet besides providing life to crops and forests that create oxygen that needed to purify the air we breathe. It’s fed by evaporation from the ground that goes through a long journey that will never end moving from liquid form to gas than liquid form again.

Rainwater is relatively pure of contaminants mainly because of how it got to where it is through the process of Evaporation which is the natural filtering process of Distillation. Rainwater has a natural Alkaline pH that neutralizes the acids built up acids that we store over time. Natural Alkaline water can be good for your health and Digestive systems. It can have a detoxifying effect on your immune system and because its softer meaning it lacks the minerals that water from down here on earth, it is good for your hair and skin.

Rain is mostly clean and safe to drink but can pick up pollutants, dust molds, and in some cases radioactivity that is in aerosol in the atmosphere on its way down to the earth. If you live in a low populated urban area than yes your water is clean. If you live in a city it is not recommended to drink rainwater or use it for cooking, showering or bathing. This is mainly because rainwater in the city may contain heavy metals and other toxins from air pollution. Use your common sense. What you see in the sky coming from a factory off in the distance will likely end up in your harvested drinking water.

Storing Rain Water

If you are thinking about Harvesting Rainwater and you live in a house with a roof well, you’re in luck your roof is a natural Rain Harvesting machine that is able to collect a huge amount of Rainwater with a minimal amount of equipment and low cost. There are a few ways to go about it.

  • Using Rain Barrels-The easiest and the cheapest way to go. Simply putting a barrel at the downspout of your roof using a Diverter that you cut into the downspout.
  • This way involves a larger container that can take advantage of fewer storms with a larger collection of water, usually a 55-gallon drum or a few in series.
  • A larger tank is located at a distance from the house normally underground at levels that are lower elevation
  • In all cases, Gravity does the work-but a pump can also be added to your system’s plans

Not only will the Rainwater Harvesting save money on water but it can correct flooding and drainage problems that may be happening on your property that eventually may damage your home.  In an earlier article I wrote herein MyWaterEarth & Sky I went over cost and an easy procedure for harvesting rainwater from your roof called What is The Cheapest Way to Collect Rainwater

If you are storing the water for an Emergency: You need to pick up an FDA-grade Food Grade water storage BLUE container that will last indefinitely depending where you store them. Each drum has 2 bung holes at the top that will accept a barrel pump. You can purchase a food-grade plastic pump and a Bung opener for the Drums that are all available and inexpensive. 

These barrels are made of High-density Polyethylene UN-DOT certified plastic can that is made to store liquids safely. Try and keep them inventoried, slightly above the ground, in the shade and out of the sun. 

The drums are pressure tested and leak proof and come in 15-30-or 55 gallon capacity. Cost Approx. .$79.00-$99.00 or recondition used for about $49.00 or half the price of a new one. Blue is coded for drinking water. In the event of an emergency, it won’t be confused with any other kind of liquid. In a survival situation or for disaster preparedness color codes are used in identifying chemicals and liquids that are in store in containers. It’s a good idea even if you are using it now for the garden. Some cities even hand or sell the barrels out to residents for the intention of promoting Rain Harvesting and Green Initiatives. Container size is up to the Harvester and how much water or how elaborate you want the system. These Food-Grade Drums can be found on Amazon some have spigots so you won’t need the use of pumps for the Drums.

Pre-treat Potable Water Drum-If you are using the Barrell or 55-gallon drum for storing and eventually for potable water supply you will need to treat the Drum before filling it. Sanitize the Drum the same way Municipal Authorities sanitize water lines after they are constructed.

  • Super chlorinate the inside of the container 
  • Use a full cup or 2 of 6% Sodium Hypochlorite (it comes in 4 & 6 %) Use Unscented Bleach.
  • Cap the drum and roll it around so as to try and make contact with the walls inside and the Bleach.
  • Run a garden hose through the opening and rinse it out.
  • Add it to the Rainwater system of drums at the downspout of your roof

How To Filter Rainwater From Roof

Before you fill your Barrels to store the Rainwater, there are a few things that need to be thought out. Rainwater that will be used for gardens, plants, and cleaning won’t need much pre-filtered before they are stored but Rainwater sourced from a roof that will be used for Potable water or for drinking will need some preparation. The first flow of the rainwater from your roof or flat surfaces like Solar Panels that are excellent ways to collect large amounts of rainwater carries with it some leaves, dust, insects, and animal droppings. With that, it is best to use a detachable downpipe so you can divert the first flow of the rainwater then pre-filter your remaining drums or containers.

Contaminants in water may include algae, air pollution, bird excrement, and leaves, sand, and dust. Local wells have dealt with these problems for decades. The installation of filtration and purification equipment can remove these contaminants at home as well. The way to handle the water coming from the roof should be to filter large particles that are washed from the roof than to divert the rain gutters into the 55-gallon drum which contains a pre-filter material for the water entering the Drum that will be used as potable water.

Preliminary Flush Drum – You can use a preliminary flush tank that will be used for cleaning the roof and then switch over to other drums. That could be handmade and start from trapping 30 mesh-like leaf catchers then move down in size to smaller sentiments and material ultimately removing material that will be involved with the harvested rainwater. The rule of thumb for water disinfection is that the more inorganic and organic solid material you remove the easier it will become to purify the water yo collect. Since Harvesting Rainwater has become popular

Downspout First Flush Diverter– When it starts to rains, water slowly builds up in the roof gutter system before it exits through the downpipe. The first flush of water from the roof can contain bacteria from decomposed insects, lizards, birds,  and animal droppings and concentrated tannic acid. It may also contain sediments, water borne heavy metals, and chemical residues, all of which are undesirable elements to have in a water storage system. This organic and inorganic material will only contaminate the water in the drum while it stored over a length of time. The Diverter has no mechanical or electrical parts. The Diverter can easily be emptied and reset after a rain event.

Leaf Screens-Leaf screens are simply screens installed over either the gutter or downspout to catch leaves and other large debris from rooftop runoff in gutters. Leaf screens must be regularly
cleaned to be effective; if not maintained, they can get clogged and prevent rainwater from flowing into the storage tanks. Built-up debris can also harbor bacterial growth within gutters or downspouts

Bung Filters- That easily fits inside the bung opening of the drum and can be removed and reinstalled very easily for keeping material out of the water supply. All these stages of pre-treatment work just like physical filters do that will make the filtering process start big and work smaller with each stage keeping them from clogging up.

How to Purify Rainwater

After you fill drums with rainwater store them in a shaded cool place out of sunlight and heat and off the ground. This will make them messy to access when it’s time to empty them.

Some people I see writing articles on the internet are recommending the use of Granular Chlorine or other Swimming Pool Disinfecting chemicals.

  • Don’t use Chlorine products used for swimming pools
  • Use Bleach Don’t try adjusting pH or any other control test. 
  • Liquid Chlorine will raise pH levels in the Drum
  • Use Safe-T-Proof STP-EQS-WPC-04 Multi-Pack Water Preserver Concentrate– this product is good for as much as 5 years. This is a proven product and is premeasured 55 Gallon Water Preserver Concentrate 5 Year Emergency Disaster Preparedness, Survival Kits, Emergency Water Storage, Earthquake, Hurricane, Safety. This product is Made in the USA! Recognized and licensed by the U.S. and state EPA’s.
  • 128oz Purogene Drinking Water Treatment and Water System Sanitizer. Eliminates Bacteria in Water, Sanitizes Water Storage Systems, Provides for Long-Term Storage of Drinking Water  This is Chlorine Dioxide EPA Registered as a safe and proven used by Water Distribution systems and treatment plants around the country. Used for over 50 years for drinking water. This product is long-lasting and effective. You can add dosage to your 55-gallon drum which is approximately 2 tablespoons per dose once a year. I like the premature long term Water Preserver because you can add the Concentrate and seal the Drum without having to open it again. But both ways are will do the job.
  • Inventory your Drums add Date-for the simple reason that you will know what drum comes offline and the date the Water Preserver Concentrate is added!


How to Filter Rainwater for Drinking at Home

Once your Rainwater is stored and now ready to be consumed there is one more step for the Harvested Rainwater. Carbon and Micro-Filtration. The best way for doing this without an elaborate system that is built-in is to use a Gravity Filter that shares both a Carbon Filter along with a Micro Filter. Again we are talking about Potable Drinking water that will be consumed by your family. If you are using the water for outside gardening and a supply that is used for topping off the swimming pool keep this supply separate from drinking water. The non-potable water can be pumped out of barrels with a transfer pump using regular garden hoses.

With Rainwater Drums that will be used as drinking water sources, there should be one last treatment. Activated Carbon & Reverse Osmosis that would ensure complete Biological and Chemical and Heavy Metal removal. This should be done even if the smallest amount of contaminants are in question.

Roofing materials are involved with the first minute the water washes down to the gutters and ends up in the drum that collects the rain. The longer the dry spell is between the rain events the more contaminates and bacteria are collected and leached from the roof and washed down into the Harvest equipment. It works like roadways during summer months when materials that are very similar to ones that make roadways are separated by the heat and lack of precipitation then washed away in the first minutes it starts to rain. This article called Why Do Roads Get Slippery After a Summer Rain from MywaterEarth& Sky shows how the same type of toxic chemicals used on roads are used in construction and roofing material and how they are affected and separated by high heat in the summer. 

Conventional roofing materials like asphalt fiberglass shingle, Galvalume! metal, and concrete tile) and alternative roofing materials were examined for their suitability to harvest rainwater for domestic drinking water use. pH, conductivity, TC, FC, turbidity, TSS, nitrite, nitrate, DOC, metals, VOCs, and SVOCs were measured in harvested rainwater. and found to need more treatment to be safe. Asphalt, bitumen, and tar, their types, and comparisons of their properties are discussed. Asphalt, bitumen, and tar have similar properties generally used for pavement construction. With Micro Filtering and Reversed Osmosis and Activated Carbon, the rainwater can be assured of its purity.

According to EPA- Rainwater harvesting is receiving increased attention worldwide as an alternative source of drinking water. Although federal agencies such as the USEPA acknowledge the existence of rainwater collection systems, the monitoring of this water source is still typically carried out by the individual state or regional health agencies. States such as Texas, Ohio, and Hawaii are developing guidelines for the use and maintenance of these types of systems. It is most likely that this water source will eventually be regulated like other public drinking water sources according to the U.S. Safe Drinking Water Act of 1986. Whenever governmental agencies become involved in regulating systems, there are a number of challenges in complying with their sometimes complex regulations. Under present guidelines, collected rainwater will be characterized as a type of surface water. Existing EPA regulations for surface water sources will be discussed along with steps users can take to understand what will be needed to meet this type of regulatory activity.

Here’s the thing, Most of the world has some kind of water problems such as flooding, drought, water shortage, water pollution, heat island are all related to rainwater. By proper rainwater management, we can reduce the risk of some of the problems we face today. To solve the (SDG) Sustainable Development Goals for drinking water by the process of Rainwater Harvesting, innovations in technical, economic, and social aspects are necessary along with a person’s individual commitment towards global health. With new technology and products to make it easier, Storing Rainwater can be done for numerous years,  on a very large scale built into the biggest city or in your own backyard.

“You just never know when you’ll need some Extra Water Save it for a Rainy Day”






References: IWA- International Water Association

Science Direct- The effect of roofing material on the quality of harvested


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