Category Archives: How-to

Rainwater Collection in Washington State: Where to Begin?

gutter-484684_640We want to keep our families safe, but when we read stories about sustainability, water conservation, saving the environment, aging infrastructure, even poisoned public water systems – how on earth are we supposed to know where to begin when it comes to rainwater collection?

Here are some tips that can help you decide where to begin. 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.

Rainwater Catchment System Key FactorsIf 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 quote.

How to Move Collected Water From Tank

submersible-pumpTo move collected water from a tank for filtration and then use, installing a submersible pump or centrifugal pressure pump is necessary to get the job done. Additionally, if you go with a submersible pump, it will also need a way to manage and regulate movement.

A pressure tank with a pressure switch will tell the pump when to turn on and off by a drop of pressure in the pressure tank. This application is much like well system and is intended for household use. It could be used for irrigation, but keep in mind that the pressure tank will need to be frost protected.

centrifugal pumpThe most common method of conveyance would be a booster pump. These pumps are generally centrifugal pumps and can be placed in the mechanical room or well shed.

A centrifugal booster pump is used without an exterior pressure tank and is considered an “on demand” pump, meaning that when the faucet is opened, the pressure in the pump drops down to low pressure – usually 20 PSI, and the pump will start running and maintain constant pressure while the faucet is open.  Once the faucet is closed, the pump will continue to run until it meets its high pressure cut off.

It is important to remember that either pump system should always be used before filtration and disinfection.

This was first published as Part 7 in the series “How to Build a Rainwater Collection System”.  Click to see parts onetwothreefour,  five and six.

How to Ensure Stored Rainwater is Clean

RainBank Rainwater Systems installs gutter screens and Wisy products to ensure water being collected is as clean as possible before storage. 

Collected rainwater should be free of organic matter before entering the storage tank. This can be achieved with a quality gutter screen and the use of pre screening or filtering to remove debris and aerate the water before storage.

Pine needles, leaves, and other debris can cause collected rainwater to become fouled with decaying organic matter. These contaminants can be a host or food for bacteria, causing your collected water to become septic. Accumulated debris generally piles up in turns in the conveyance lines and can fester over time. Water passing through these pile-ups will pick up odor, discoloration, and bacteria, resulting in fouled water entering your storage tanks.

Care must be taken to ensure that water being stored is as clean as possible. The use of gutter screens will reduce the chore of gutter cleaning, but do require a certain amount of maintenance. Periodic cleaning of screens should be conducted as needed. When pine needles or leaves pile up on gutter screens, they need to be removed. This can be done with a garden hose or a brush and is a lot less work than cleaning the gutters themselves.

Quality of stored water can also be improved by the use of Wisy products. Before entering the storage tank, rainwater should be filtered and aerated. Filtration removes particulate matter, which frequently carry and feed bacteria. Removal, along with aeration, greatly reduces the amount of bacteria in the storage tank.

The video below shows how debris falls to the bottom of the filter, while the desired water is sent through a screen horizontally, and then clean water can be conveyed to storage. The vortex filter requires very little maintenance and is as easy as removing the screen and washing.

Rainwater is relatively clean to begin with; it is what it comes in contact with that needs to be addressed. By gutter screening, filtering, and aerating rainwater before storage, you will be assuring that your stored water is of the quality you desire while helping  filtration and disinfection for end use.

Lopez Tanks

RainBank Rainwater Systems is the leader in designing and installing rainwater collection systems in the Seattle area for more than 15 years, and is preferred by homeowners, architects, and engineering firms for its quality solutions to rainwater harvesting. We offer engineered systems for potable and non-potable systems, commercial and residential.