One of the most important considerations when designing a rainwater harvesting system is what you intend to do with the water. Almost everything follows from this aspect. Tank size, delivery method, water quality, and overall system cost are all affected by this decision. Carefully consider changes that may occur in the future when making this determination. If there is a possibility that rainwater may one day be used for drinking, then the components of the collection and storage facility will need to be approved for this use. It is not a good idea to install a secondary use system and then push it into beverage service. It would be better to add a second discrete system for potable water, in this case. If you intend to use the water indoors, it’s probably best to consider the system potable, even if you never expect to drink the collected water.

Water efficiency experts who tracked data from three water districts over two years concluded that a rainwater harvesting system, used only for irrigation, that substitutes 40% of the water needed for this purpose, will recover its cost in approximately 4 years. Indoor water conservation techniques, including low-flow faucets and showerheads, high-efficiency dual-flush (HET) or ultra-low-flow (ULFT) toilets, water-conserving appliances, and composting toilets, were also tracked. with various results. The bottom line is that embedded systems cost more and take longer to recover. Exclusive outdoor use has the best return on investment, but lacks versatility. You must decide what is important to you.

Irrigation and other external uses

Irrigation is one of the first things that comes to mind for most people when they think of collecting rainwater. It makes a lot of sense not to buy potable water for irrigation. In fact, there is some evidence that chlorinated water damages the biological health of the soil and therefore decreases production. Other external uses of water that work well with rain is washing vehicles, as it is soft and does not leave limescale deposits that damage delicate finishes and fountains and ponds that do not benefit from chlorination.

If your water district enforces outside water use restrictions, they do not apply to collected rainwater. Using rainwater does not incur a sewer charge or overburden aging infrastructure that is reaching capacity in parts of the country and the world. We can all help extend the amount of time our government entities have to deal with this problem by using less tap water for purposes that don’t require it.

Secondary indoor use

Toilet flushing and laundry accounted for about 40% of indoor water use and do not require tap water quality. Again, softness is a plus when it comes to these accessories around the home. Less soap is needed to get the same level of cleanliness, and clothes are not damaged by deposits left behind when using hard water. Toilet valves and traps stay cleaner when soft water is used. The sewer bill is based on consumption, so your water bill is reduced in two ways when rain replaces tap water for indoor secondary use.

potable use

Bathing, cooking, dishwashing, and drinking are considered potable uses in most cities and water districts, and some states restrict the use of collected rain for these uses, especially when the property is connected to a public water supply. Check your local codes and ordinances before attempting to use indoor drinking rain. If your property is not connected to a public supply, then there are several published university studies that verify that rainwater is safe for human consumption if carefully collected and stored. Some 30,000 years of human occupation of the planet supports these studies with historical data. Rainwater quality is a function of air quality, so there are areas where heavy industrial facilities, livestock operations, or volcanic activity could create a problem, but these can be counteracted with proper treatment. If you suspect something like this is happening in your area, have your cistern water tested and corrected, if necessary.

Rainwater is slightly acidic; in most areas averaging around 6.5 pH. This can be buffered by adding a small amount of USP Grade Calcium Carbonate. The less desirable baking soda (baking soda) can be used, but it also adds sodium to the water. If you have an unlined concrete cistern, the calcium present in the concrete will buffer the pH to some degree. Most people don’t bother to add anything to their cistern, and it’s very important not to add disinfectants like chlorine unless an unusual event occurs that contaminates the water with toxic microbes.

Owners have removed drowned raccoons from their cistern without disinfecting the water and have not noticed any problems. There’s a limit to how much of this kind of thing can be tolerated, but a minimally maintained cistern develops a healthy biofilm on the inside that contains a colony of beneficial microbes that control the less desirable ones that come in with every rain or event. of wildlife. However, if rats enter the cistern, they carry a disease-causing microbe in their urine that may need to be countered.

For safety, it is recommended that a stormwater drinking system use some method of disinfection or purification after flushing. This can be as simple as a point-of-use or faucet-mounted device or as elaborate as a whole-house ultrafilter or UV water treatment unit. The most popular option is a UV system with a carbon filter. These units are easy to install and maintain, but it is important to have good water clarity and change the UV bulb once a year to ensure they are effective. Ultrafilters do a different job, they purify water by filtering out microbes instead of deactivating their DNA and leaving them in the water but unable to reproduce like UV rays do. The effect is the same but the difference is significant for some people. Adding chlorine has multiple effects in addition to disinfection, such as reacting with other elements that may be present in the water and leaving by-products that can be harmful. Few owners use chlorine for anything other than cleaning the cistern and pipes before initial use. This ensures that nothing resides in the system that could flourish in untreated water. After that, adding chlorine should be considered a drastic measure reserved for drastic circumstances.

holistic approach

An integrated system that combines potable, secondary, gray and black water recycling is the ultimate in water efficiency and self-sufficiency. Few of these systems exist, but more are coming online every day. The Leadership in Energy and Environmental Design (LEED) and Living Building Challenge movements are prompting more and more people to reevaluate how they choose to live on the planet and how they interact with society. The integration of all aspects of life is being considered, reaching far beyond the needs of survival.