Category Archives: Potable

Potable, Rainwater Catchment

Is Rainwater Clean and Safe to Drink?

clear-water-glass_smRainwater is generally considered clean to begin with, however, water is an excellent medium for growth and transport of disease causing organisms.

The good news is rainwater is relatively easy to filter and disinfect, and disinfected rainwater may significantly improve drinking water supplies.

The clean water act of 1974 and recent amendments have enhanced the protection of drinking water. But, news bulletins throughout the United States of contaminated municipal supplies have spawned an increased interest in rainwater harvesting as a source of drinking water. People are looking toward alternatives to an aging, overwhelmed infrastructure to provide a safe, clean source of drinking water for the household and family.

Water quality problems associated with rainwater harvesting systems most often originate in the catchment area, conveyance system, or storage components caused by:

  • System was poorly maintained
  • Collected water was not properly disinfected
  • Conveyance and storage were poorly designed
  • Simple measures were not taken to ensure the quality of the water

All harvested rainwater that is intended for potable use must be treated effectively to minimize the risk of harming human health. To ensure a RWH system is producing high quality water, proper techniques in design, construction and maintenance along with testing need to be conducted.

Recent plumbing codes set by the American National Standards Institute (ANSI) and American Society of Plumbing Engineers (ASPE) along with the American Rainwater Catchment Systems Association (ARCSA) have been adopted at the national level and must be adhered to by designers and contractors installing rainwater collection systems meant for potable and non potable use. 

Rainwater harvesting can be a safe, reliable source of drinking water if codes and practices are conducted. Ask if your designer and installer are ARCSA Accredited Professionals and are up to date on the latest plumbing codes. 

Infrastructure, Potable

Rainwater is a Safe Source of Drinking Water

gutter-pipe-54531_640We know we can effectively capture, store, and use rainwater as a safe, viable source of potable water (drinking water) in Seattle and the Pacific Northwest.

A temperate climate offers rainfall throughout the year, including a little in most summers. With low intensity and high frequency rainfall, storage volume to use ratio is close to ideal. The autumn rain returns cisterns to high levels after summer usage and winter’s increased rainfall keeps them at optimal levels. As spring arrives, cistern levels continue to be supplied by less rainfall, but enough to allow summer demands to be met. The Pacific Northwest does not witness an extended “hard freeze” in the winter months as other parts of the country, allowing storage to be unaffected by most weather conditions. Marine winds help keep our air quality above average, with limited pollutants affecting quality. The same weather systems that produce snow caps for our municipal summer supplies also comes to us as rain in lower elevations, which can be stored for immediate and future use.

Storage is calculated by annual and monthly amounts, intensity, frequency, return period, and maximum number of dry days along with catchment area and surface runoff coefficients. Use or demands are based on number of occupants, fixtures, evaporation, efficiencies, indoor and outdoor requirements. Supply and demand equilibrium is compared to determine storage capacity, surplus/deficit, and level of storage. The frequency, return period and monthly amounts in Seattle and Puget Sound region can support whole house, year round use of rainwater collection.

An average 2,250 sq ft house in the Seattle area has the potential of collecting more than 53,000 gallons of water from its roof, rather than entering the storm system and accumulating contaminants before discharging in our waterways. Residential and commercial new construction is mandated to disperse roof runoff onsite, which is a good step toward protecting our waterways. But, why not use that water for our needs? Absorption type filtration, ultra violet light disinfection along with proper design, construction, and maintenance will allow homeowners to easily become their own purveyor of their own water source.

While most municipal water supplies are safe in the US, the recent water crises in Michigan and Ohio have brought public concern of quality and safety of our centralized water supplies. Costly repairs and replacement of an aging centralized water system will be required in the next 20 years. Rainwater collection is a viable, safe source of potable water for the homeowner in many counties in Washington State and elsewhere in the US and should be considered by those who don’t.

Rainwater collection helps protect our environment, conserves energy, decreases water contamination, helps prevent flooding, erosion and sewage releases into our waterways.

Tell your local government that you would like to see rainwater collection for single-family home potable use.

Potable, Rainwater Catchment

Does Rainwater Need Treatment for Drinking?

clear-water-glass_smAlthough it is fairly clean at the outset, when it comes in contact with impure surfaces, rainwater may need some treatment before drinking. A rainwater collection system designed with filtration and disinfection will get the job done.

Harmful bacteria, pathogens, and cysts removal is a must in a potable (drinking) rainwater collection disinfection train. This is typically achieved with a class “A” UV light. Flow rates are calculated to achieve the correct amount of contact time with the UV spectrum for proper disinfection. The correct class of UV for a specific application is required. A class “A” UV must be used for water that is not deemed safe to drink. A class “B” is only used for water that has already been safe to drink.

But there are other considerations for water treatment. The raw water must be relatively free of sediments, turbidity, organics and inorganics before entering the UV chamber. The UV spectrum will not be able to penetrate the water column effectively otherwise. Special consideration of environmental constituents should also be addressed for proper treatment.

Environmental concerns can include location of collection area. Where is the house located? Possible hydrocarbons from a nearby freeway would be a concern. Pesticide use from farming or city landscaping maintenance should be considered. Roof material and manufacturing process could pose a health threat and should be addressed – all of which can be corrected with proper filtration, whether it is accomplished with canister elements or back flush devices.

Rainwater is typically acidic, approximately 5.5 to 6.0 ph; nominal being 7.0 ph. The lower ph levels, while not considered harmful to humans, can have a negative effect on plumbing and fixtures. A more nominal ph level can be achieved with proper treatment.

RainBank Rainwater Systems designs and installs custom treatment systems to meet customers’ specific needs.

This Throwback Thursday post was originally published under the title Considerations for Water Treatment