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Rainwater Harvesting FAQ's

"How do you harvest rainwater?"

Rainwater is harvested by diverting rainfall from impervious surfaces (such as roofs) to a storage vessel to be utilized for future purposes.  This can be done several different ways.  Rainfall can be captured by methods as simple as a barrel underneath a gutter downspout or as complicated as tanks capable of storing thousands of gallons of water to be filtered and used for drinking inside the home.  The possibilities for collecting rainwater are both exciting and virtually limitless.


"What is the best way to harvest rain?"

The best method primarily depends on your intended use for the reclaimed water. 

Simply allowing run-off to collect in a barrel is ideal for watering small flowerbeds and potted plants.  Although these barrels look large, they hold a relatively small amount of water and would not be suitable for sustaining even a small lawn through a hot summer. 

Small garden patches and native landscapes would best be served by a slightly larger storage vessel, like a 1,500 gallon tank constructed of plastic, fiberglass, or galvanized steel.  The larger the storage vessel utilized, the larger the collection area should be in an effort to maintain water in storage throughout a season.

Larger more complicated systems are not recommended for Do-It-Yourselfers.  Contact an accredited rainwater harvesting professional in your area.  You can find one by visiting  


"Do I need pumps to harvest rain?"

It is not typical to need a pump to harvest rain, however, a pump may be necessary for pressurizing a distribution system, like a whole house water system or irrigating large areas. 

Occasionally a pump may be necessary if the primary storage vessel is placed higher in elevation on the property.  This pump would allow you to collect the rainfall from a lower elevation and pump it into the storage container.

Simple collection systems consisting of barrels or those with a relatively close point of use do not require a pump as they can utilize gravity to dispense the water.


"Can I use soaker hoses or drip irrigation with rainwater?"

Yes.  Soaker hoses and drip irrigation can be used with rainwater although not all hoses and irrigation systems are suitable for all scenarios.  The primary determining factor is whether or not a pump is used within the system.  The incorrect type of irrigation can compromise the effectiveness of your water usage.  Consult your local accredited rainwater harvesting professional for clarification on which irrigation methods will require the use of a pump.


"What can I do with collected rainwater?"

Rainwater can be used anywhere water is typically used.  In order for rainwater to be potable (suitable for human consumption) it should be treated to EPA standards.

To view the EPA codes and standards visit:


"Is water quality an issue RW collection systems?"

Yes.  There are different levels of water quality dependent upon final use intentions. Most rainwater is of adequate quality for use in landscapes and other non-potable uses with minimal filtration or treatment. 

Refer to or or contact your local accredited rainwater harvesting professional.


"Are there differences in roof efficiencies when capturing rain?"

Yes.  Porous roof coverings will absorb the initial rainfall until saturated to the point of reduced surface tension.  The ideal roof covering for collecting rain is metal roof material with appropriate coatings dependent upon use.   Roofs of low slope will absorb more water than roofs of greater slope.


"How much rainwater should I harvest?"

It is recommended to identify intended uses prior to incorporating a rainwater collection system as the size of the system is relative to average local rainfall, roof footprint area, and volume of water needed for intended usage purposes. 

Once the desired amount of water is identified, it is then possible to establish a catchment method that will meet such demands.


"How can I remove algae?"

Green algae, those we see in water storage containers, is the most diverse group of algae with more than 7,000 species growing in a variety of habitats.  By minimizing organic materials prior to storage and eliminating sunlight penetration from your storage vessel, you should not experience algae growth.  If you experience the growth of algae, it is recommended that you identify the source of sunlight penetration, drain and clean tanks, seal penetration locations, and prepare for your next rain event.


"What about mosquitos?"

Rainwater harvesting systems should be constructed with pre-filters and screens on all inlet and overflow devices to prevent the intrusion of insects and vermin such as mosquitos and rodents.


"How much does a Rainwater Harvesting system cost?"

The cost of rainwater harvesting systems is relative to the size of the system and its intended use.  A simple system might start at a few hundred dollars with a complicated, potable water system as much as several thousand dollars.  Each system is unique in it’s location, design, and intent and therefore are not typically available at a flat rate.


"How much water can I realistically collect?"

To calculate the amount of water your location is capable of collecting use this formula:

Building footprint area x inches of precipitation x 0.6 = potential total volume of rainfall in gallons


1000 sq. ft. x 2” of precipitation x .6 = 1,200 gallons

This formula includes approximately 2.5% loss to roof absorption, splashing, and pre-filtration.


"Can I incorporate RW storage into my landscape?"

Yes.  There are a wide variety of storage options to incorporate into any landscape.  Most storage tanks are above ground and are only buried when surface area is at a premium.