Rainwater Catchment

Key Factors In Planning a Rainwater System

Water. We simply can’t live without it. Safety, cost and convenience are some key factors to consider when planning a rainwater system for commercial or residential use. Will the water be used for irrigation? Toilet or laundry facilities? Or, will you and your family want to drink it?

Here are some key factors to help you decide where to begin designing your system. We originally discussed this in a post from 2014:

Whether you are designing your own rainwater catchment system or having one designed by a professional, success of your rainwater catchment system design is dependent on some key factors.

What do I want to accomplish with my design of a rainwater catchment system?

Irrigation, toilet and or laundry facility, supplementary to well water or city water, whole house usage, and sole source are the main purpose of designs.

How much rainwater can I collect from my roof? Will it be enough to supply my needs?

One inch of rainfall per 1,000 square feet of roof will yield approximately 623 gallons of water. Evaporation, wind, and spillage account for 15 – 20 % of loss. A 2,000 square foot roof with 36″ of annual rainfall may yield 44,856 gallons. With an efficiency of 85%, that equals 38,128 gallons.

One inch of rain is needed for the healthy growth of plants. This equates to .623 gallons per week for 1 square foot of planting, which can add up rather fast, so keeping your irrigation needs small and giving consideration to drought tolerant plants is recommended.

Toilet and laundry facilities account for 49% of household usage. Designing and building a system for this purpose alone can cut your water and sewer bill in half. New construction is the best time to implement this type of system however, retrofitting plumbing in an existing home can be accomplished.

If the collection area is small or available space for storage is restricted, a supplementary system can be achieved with “slim line” style of cisterns or buried tanks. A small roof can still be effective in collection if used for a supplementary source to well water or city water.

Whole house usage, or potable water, can eliminate dependency on city water or well water, where you can still have city or well water as a back up during dry times. With the advanced filtration and UV disinfection offered today, safe, reliable drinking water for whole house usage will exceed the quality of most well and city water.

Now that you are considering what usage of collected rainfall would best suit your needs, we will discuss sizing, configuration, implementation, and maintenance of a designed rainwater catchment system in upcoming posts.

When you are ready to begin, RainBank will come to your site, discuss your needs and prepare a feasibility study – customized to your usage. There is a fee for this, which would be discounted from the cost when you contract with us to design or build your system. Use the form below to request a feasibility study.

Potable, Rainwater Catchment

Poorly Designed Rainwater Harvesting Systems

Poorly designed and maintained rainwater harvesting systems can be more than unpleasant.

As many others did, I built a house in the Puna district of the Big Island of Hawaii in the 1980’s. The inexpensive properties of the subdivisions above Hilo provided an opportunity for home ownership to those who could not otherwise afford to build. The subdivisions were created in the 1960’s and 70’s as agricultural, with little infrastructure, certainly no water source. As everyone else did, I built my own rainwater catchment system, designed based on what everyone else was doing. The county provided “city water” stops along Kamehameha Highway, for drinking water for those on rainwater catchment. All other household water use was provided by the catchment system with little filtering and no real disinfection. UV disinfection was not available for small water systems at that time. 

Many systems were owner built and consisted of a “pool boy” – an above ground swimming pool with a non potable liner. There were some corrugated steel and a few cement or wooden tanks. Many of the roofs were asphalt shingle, causing a bit of a sheen on the water surface during the hot day. A sediment filter prior to the pump was the typical filtration train and, as mentioned, no disinfection. But, no one was drinking it as far as I knew. 

For decades there were no regulations for rainwater catchment systems in Hawaii. Systems were built with not much consideration of public health. Essentially, a large community with no oversight to standards or safe practices. Now, many of these antiquated systems are being contaminated by slugs and snails which have been found to carry “rat lungworm parasite”, a potentially devastating disease. Please see below article.

Water Catchment Systems Need to be Properly Maintained

Rainwater catchment can be a safe, viable alternative to ground water “IF” proper best practices are followed. The industry has grown considerably, along with most states having some type of regulations and permitting.

ARCSA/ASPE/ANSI 63 has been adopted as code by most municipalities that allow rainwater collection for potable use. ARCSA Accredited Professionals are trained and must participate in continuing education in order to keep their accreditation. Designs for permitting are being submitted to Health Departments for plans review. Inspections by county plumbing inspectors during construction of systems is common with bacterial sampling required by some.

It is not the 70s and 80s any longer and rainwater catchment for potable use has hit an all time high here in Washington State. Systems are being designed and installed by professionals that have the training and experience needed for the well-being of their customers. Check with your contractor to be sure they are ARCSA Accredited and know the code requirements. By doing so, you will be assuring that your water source is safe for you and your family.

Potable, Residential Rainwater Collection

Skagit County Water Source

RainBank Rainwater Systems has broken through the barriers that have restricted rainwater collection as an approved water source for single family residences in Skagit County.

With the instream flow rules,  many property owners in the Skagit River Basin were unable to develop their properties. WA State Department of Ecology encouraged Skagit County to adopt the practice as a solution that would benefit the river and salmon habitat, while providing a viable water source. Limited permitting for the affected areas was considered as recently as 2015.

A group of residents from Guemas Island petitioned the county to accept rainwater for potable use for homes that were experiencing salt water intrusion in their wells. RainBank Rainwater Systems, along Tim Pope, ARCSA educator and past president, met with Skagit County in January 2017 to encourage acceptance of potable rainwater collection as a viable alternative source, not only in the instream flow rules affected areas but to those who are experiencing other hardships regarding potable water.

RainBank Rainwater Systems is pleased with the recent design approvals from Skagit County for potable residential RWC systems outside the instream flow rules, allowing for more property owners in Skagit County. We look forward to assisting Skagit County residents with their dreams of developing or purchasing properties with limited water resources.

Rainwater Systems