Rainwater Catchment System Key Factors

Rainwater Catchment System Key FactorsWhether 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.

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How Safe Are Our Water Supplies?

How Safe Are Our Water Supplies?
Algae-infested water from Lake Erie on Monday washed up onshore at Maumee Bay State Park in Oregon, Ohio, near Toledo. Credit Joshua Lott for The New York Times

The recent news about Toledo’s water supply being affected by a toxic algae bloom, disturbing  over one half million customers, has us asking once again – how safe are our water supplies?

It wasn’t too many months ago that the coal spill in the West Virginia river had residents scrambling for an answer.  Aging infrastructure, with its inherent problems of failures causing water boiling advisories, are becoming more common. The use of fertilizers and insecticides are migrating into our water supplies. Industrial urbanization is leaching toxins into our waterways and wetlands, eventually ending up in aquifers, lakes, and reservoirs.

The National Resource Defense Council has asked for the Federal government to step in and find a solution to this problem.  However, the Fertilizer Institute is part of  a coalition of industry and agricultural interests that are opposing Federal efforts to restore some coverage of the Clean Water Act.

Centralized water is being threatened by many facets. A decentralized water system may be the answer to a safe drinking water supply for us all.

How to Offset Costs of Stormwater Regulations for New Construction

How to Offset Costs of Stormwater Regulations for New ConstructionNew stormwater regulations for runoff and green storm water infrastructure are adding to the costs of new residential and commercial construction in Seattle and elsewhere.  Infiltration of runoff from roofs, driveways, and all impervious surfaces are mandated by local and Federal agencies. While infiltration does help reduce storm water runoff, the added costs of implementing infiltration or a rain garden can be considerable, with no return on investment for the home owner or building’s owner.

By directing costs of designing and implementing an infiltration system or rain garden to a rainwater collection system, the builder can mitigate stormwater runoff to a useful purpose. Irrigation,  toilet, laundry facility, and whole house (potable) usage can be supplied by rainwater collection, storage, and use, lowering monthly water and sewer bills.

The Seattle times recently reported on rate increases over the next 5 years for water and sewer, to meet the challenges of expansion and repairs to an aging infrastructure. Approximately 6.2 billion dollars are expected to be needed over the next 20 years for expansion and repairs to the existing infrastructure in the Puget Sound region as a whole.

How to Offset Costs of Stormwater Regulations for New ConstructionHow to Offset Costs of Stormwater Regulations for New ConstructionWhile the average monthly billing increases are not enough to pay for a rainwater catchment system, the costs of designing and implementing an infiltration system or a rain garden are significant enough that if redirected to designing and building a rainwater collection system along with lower water and sewer bills, a homeowner or building owner will recognize a return on investment.

A well designed and implemented rainwater harvesting system for toilet and laundry facility for a single family residence can save 49% of their city water usage with a small amount of storage. Using the available water from roof runoff rather than just infiltrating it into the ground makes a lot more sense and has a return on investment.