Category Archives: Rainwater Catchment

How-to, Rainwater Catchment

Is Sole Source Use of Rainwater Collection Legal in King County?

lake-176942_640There has been a great deal of inquiry about sole source use of rainwater collection in King County, causing confusion for the public – as well as for King County public officials. RainBank is currently consulting on four different projects, assisting clients with navigating the system.

A change in Department of Public Health Policy, which is the authority on single source rainwater collection, has been transferred back to the Onsite Sewage System Authority (OSS) of King County Public Health.

There is a section of Title 13 that refers to rainwater collection for single source usage. This authority has jurisdiction over sole source use; any other permitting approval for supplementary source is to be approved by King County Public Health Department’s senior plumbing inspectors. There are plumbing codes that must be met with regard to installation and permitting from KCH plumbing division for any RWC system that is potable or non potable, that is connected to household plumbing.

Below is the section of Title 13 dated November 20, 2013, which refers to sole source usage

D. A rainwater catchment system that serves as the only source of drinking water for a single family residence and that complies with each of the following conditions:

1. The health officer finds that requiring connection of the plumbing system to an approved public water source or to an approved private well would cause undue hardship.

2. Application for a rainwater catchment system source approval shall be submitted for review on forms provided by the health officer. The applicant shall pay to the health officer the rainwater catchment system review fee as specified in the fee schedule, payable after completion of the application review.

3. Application for a rainwater catchment system source approval shall be prepared by any one or more of the following:

a. A professional engineer authorized under a current, valid license to practice in Washington state;

b. An environmental health professional holding a current, valid registration from either the Washington State Environmental Health Association or the National Environmental Health Association;

c. A King County licensed water system designer holding a current, valid license to design water systems in King County; and


d. A rainwater system designer holding a current, valid accreditation from the American Rainwater Catchment System Association.


4. Rainwater catchment system source design shall conform to Part III of Chapter 16 of the Uniform Plumbing Code, 2009 edition, as amended, and shall include, at a minimum, the following information:

a. Estimated daily and weekly and annual demand;


b. Available catchment area and estimated annual rainwater capture;


c. Roofing materials used;

d. Storage capacity of and materials used in the construction of the rainwater catchment system; e. treatment specifications including filtrations and disinfection system specifications; and


f. Operation and maintenance requirements.

5. Composite or shake shingles or other materials determined by the health officer to present a risk of contamination may not be approved or used as roofing materials for a rainwater catchment system source.


6. Before using a rainwater catchment system source, the property owner shall file in the county recorder’s office a notice on title advising that the property is served by a rainwater catchment system and including the following information:

a. The estimated daily, weekly and annual water supply furnished by the rainwater catchment system;

b. That the water supply from the rainwater catchment system may be limited due to variations in rainfall or usage; and

c. That regular maintenance of the treatment system and components is required in order to minimize the risk of consuming contaminated water.

As rainwater collection becomes less of a niche and more mainstream for residential and commercial applications, and with 15 years of design and installation experience, RainBank is the go-to source and your advocate for rainwater collection systems in the Pacific Northwest. Using the form below, contact us today to learn how we can help you with proper system design, installation and consultation through the sometimes confusing permitting requirements for potable, non-potable, sole source and supplementary systems in and around Seattle, Washington state and beyond.

How-to, Rainwater Catchment, Residential Rainwater Collection

The WISY 4 Step Rainwater Collection System

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4 Step Process - RBEarlier this year, we announced that we are a WISY product dealer.

A rainwater system designed with WISY products requires minimal maintenance and never needs replacing. With the WISY 4 Step system, you’ll never clean a filter basket or a tank again.  Ever.

The WISY 4 step system.

Step 1. WISY VORTEX FILTER

Before entering the tank for storage, rainwater should be both filtered and aerated. Filtration removes large particulate matter, which frequently both carries and feeds bacteria. Removal of this particulate matter, along with oxygenation of the water, greatly reduces the amount of harmful bacteria in the tank. WISY pre-tank filters accomplish both of these tasks, protecting the water quality in the tank.

Step 2. WISY SMOOTHING INLET

While filtration removes most of the sediment and bacteria before rainwater enters the tank, a small quantity will settle at the bottom of the tank. This biofilm layer is beneficial for the tank and may remove additional bacteria and metals from the water. The WISY smoothing inlet calms rainwater as it enters the storage tank to prevent the agitation of sediment at the rainwater inlet. The smoothing inlet also helps aerate harvested rainwater by directing water upward and outward, avoiding disruption of the beneficial biofilm layer and preserving water quality in the tank.

Step 3. WISY FLOATING FILTER

Since all harvested rainwater is filtered before entering the tank, the floating filter should never clog but will instead take water from just below the surface. Water at this depth is of the highest quality in the tank, because any particulate that enters the tank either floats on the surface or settles to the bottom. In RainBank designed systems, the floating filter acts more as an uptake point for the pump than a filter; thus, the floating filter should never require maintenance.

The floating filter consists of a polyethylene ball and stainless steel filter and is supplied with a standard 7 foot length of food-grade suction hose. The nozzle connections are available in 1 1/4″ and 2″ sizes.

Step 4. WISY OVERFLOW DEVICE

To prevent backup in the system during heavy rains, the storage tank should always include an overflow protection device. The WISY overflow device has a flapper valve, which allows water to overflow but protects water quality in the cistern with backflow prevention and vermin protection. The overflow device also contains an angled opening to provide skimming of small buoyant debris, such as pollen, on the water surface.

More to come: we will offer an online shopping cart for you to make your purchases. Contact us with questions about the WISY 4 Step System.

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