| One of the most important considerations when | | | | attempting to use rain for indoor potable use. If your |
| designing a rainwater harvesting system is what you | | | | property is not connected to a public supply, then |
| intend to do with the water. Almost everything keys | | | | there are several university studies that have been |
| off of this aspect. The size of the tank, the method | | | | published that verify that rainwater is safe for human |
| of delivery, the quality of the water and the overall | | | | consumption if collected and stored carefully. About |
| cost of the system are all affected by this decision. | | | | 30,000 years of human habitation of the planet backs |
| Consider carefully the changes that may come in the | | | | those studies up with historical data. Rainwater quality |
| future when making this determination. If there is a | | | | is a function of air quality, so there are areas where |
| chance that the rainwater could someday be used | | | | heavy industrial facilities, livestock operations or |
| for drinking, then the components of the collection | | | | volcanic activity could create a problem but these can |
| and storage facility will need to be approved for this | | | | be counteracted by proper treatment. If you suspect |
| use. It is not a good idea to install a secondary use | | | | that something like this is going on in your area, have |
| system and then press it into potable service. It | | | | the water in your cistern tested and corrected, if |
| would be better to add a second discrete system | | | | necessary. |
| for drinking water, in this case. If you intend to use | | | | Rainwater is slightly acidic; in most areas averaging |
| any of the water indoors, it is probably best to | | | | about 6.5 pH. This can be buffered by adding a small |
| consider the system to be potable even if you never | | | | amount of a USP grade of calcium carbonate. The |
| expect to drink your harvested water. | | | | less desirable sodium bicarbonate (baking soda) can |
| Water efficiency experts that tracked data from | | | | be used but it also adds sodium to the water. If you |
| three water districts over two years have come to | | | | have an unlined concrete cistern, the calcium present |
| the conclusion that a rain harvesting system, used for | | | | in the concrete will buffer the pH to some degree. |
| irrigation only, that supplants 40% of the water | | | | Most people don't bother to add anything to their |
| needed for this purpose will pay back its cost in | | | | cistern and it is very important not to add |
| about 4 years. Indoor water conservation techniques | | | | disinfectants like chlorine unless an unusual event |
| including low flow faucets and shower heads, high | | | | happens to contaminate the water with toxic |
| efficiency dual-flush (HET) or ultra-low flow toilets | | | | microbes. |
| (ULFT), water conserving appliances and composting | | | | Homeowners have fished drowned raccoons out of |
| toilets were also tracked with varying results. The | | | | their cistern without disinfecting the water and didn't |
| bottom line is that integrated systems cost more and | | | | notice any problem. There is a limit to how much of |
| take longer to pay back. Outside only use has the | | | | this kind of thing can be tolerated but a minimally |
| best return on investment but lacks versatility. You | | | | maintained cistern develops a healthy biofilm on the |
| must decide what is important to you. | | | | inside which contains a colony of beneficial microbes |
| Irrigation and Other Outside Uses | | | | that control the less desirable ones that enter with |
| Irrigation is among the first things that come to most | | | | each rain or wildlife event. If rats enter the cistern, |
| people's minds when thinking about collecting rain. It | | | | however, they carry a disease causing microbe in |
| makes a lot of sense not to buy drinking water to | | | | their urine that may need to be counteracted. |
| irrigate with. In fact, there is some evidence that | | | | For safety's sake, it is recommended that a potable |
| chlorinated water damages the biological health of the | | | | rainwater system use some method of disinfection |
| soil and thus decreases production. Other outside | | | | or purification after the cistern. This can be as simple |
| water uses that work well with rain is vehicle washing | | | | as a point of use or faucet-mounted device or as |
| since it is soft and does not leave scale deposits that | | | | elaborate as a whole-house ultra filter or UV water |
| harm delicate finishes and water features like | | | | treatment unit. The most popular choice is a UV |
| fountains and ponds that don't benefit from | | | | system with a carbon per-filter. These units are easy |
| chlorination. | | | | to install and maintain but it is important to have |
| If your water district enforces outside water use | | | | good water clarity and to change the UV bulb once a |
| restrictions, they do not apply to harvested | | | | year to ensure that they are effective. Ultra filters |
| rainwater. Rainwater use does not incur a sewer | | | | do a different job, they purify the water by filtering |
| charge or strain the aging infrastructure that is | | | | the microbes out rather than deactivating their DNA |
| reaching maximum capacity in parts of the country | | | | and leaving them in the water but unable to |
| and the world. We can all play a part in extending the | | | | reproduce as UV does. The effect is the same but |
| amount of time our government entities have to deal | | | | the difference is significant to some people. Adding |
| with this issue by using less tap water for purposes | | | | chlorine has multiple effects in addition to disinfection |
| that do not require it. | | | | such as reacting with other elements that could be |
| Secondary Indoor Use | | | | present in the water and leaving byproducts that |
| Toilet flushing and clothes washing comprise about | | | | could be harmful. Few homeowners use chlorine for |
| 40% of indoor water use and do not require tap | | | | anything other than cleaning the cistern and pipes |
| water quality. Again, softness is a plus when it comes | | | | before initial use. This ensures that nothing is resident |
| to these fixtures in the home. Less soap is needed | | | | in the system that could flourish in untreated water. |
| to obtain the same level of cleaning and clothes are | | | | After that, adding chlorine should be considered a |
| not damaged by the deposits left behind when hard | | | | dramatic measure reserved for drastic circumstances. |
| water is used. Toilet valves and trap ways are kept | | | | Holistic Approach |
| cleaner when soft water is used. The sewer bill is | | | | An integrated system that combines drinking, |
| based on consumption so your water bill is reduced in | | | | secondary, grey and black water recycling is the |
| two ways when rain replaces tap water for indoor | | | | ultimate in water efficiency and self reliance. Few of |
| secondary use. | | | | these systems exist, but more are coming online |
| Potable Use | | | | every day. The Leadership in Energy and |
| Bathing, cooking, dishwashing and drinking are | | | | Environmental Design (LEED) and the Living Building |
| considered potable use in most cities and water | | | | Challenge movements are driving more and more |
| districts and some states restrict the use of | | | | people to reevaluate the way in which they choose |
| harvested rain for these uses, especially when the | | | | to live on the planet and how they interact with |
| property is connected to a public water supply. | | | | society. Integration of all aspects of life, reaching |
| Check your local codes and ordinances before | | | | way beyond just survival needs is being considered. |