Rainwater catchment systems

Choosing the right rainwater harvesting system can be confusing for those not familiar with the process. Most of our residential customers come to us knowing that they want to collect the rain but don't know how or where to use a system. The information on this page will help you to get a better understanding of how rainwater harvesting systems work and familiarize you with the various components. It will also prepare you to know what questions to ask when we come out for our first visit.

Choosing the right size

Are you looking to supplement or replace your main water source? Not sure? This will help you decide:

Watering your lawn requires at least 1″ of water per week. That’s .63 gallons per square foot once a week. Example: 10′ x 10′ area requires only 63 gallons per week, however, 100′ x 100′ requires 6,300 gallons per week. Vegetable gardens and landscaped areas require a bit less.

If you don’t know how many gallons you need from your system, here’s a simple calculator to get an approximate answer.

Square footage of your lawn
Calculate
LAWN 63 gallons

This is how much water you’ll need per week during the drier months (June, July, and August)
756 gallons

This is the total water storage capacity you’ll need to replace your main water supply with rainwater for irrigation
VEGETABLE GARDEN 47 gallons

This is how much water you’ll need per week during the drier months (June, July, and August)
564 gallons

This is the total water storage capacity you’ll need to replace your main water supply with rainwater for irrigation
LANDSCAPE PLANTS 32 gallons

This is how much water you’ll need per week during the drier months (June, July, and August)
384 gallons

This is the total water storage capacity you’ll need to replace your main water supply with rainwater for irrigation
LAWN 63 gallons

This is how much water you’ll need per week during the drier months (June, July, and August)
LAWN 756 gallons

This is the total water storage capacity you’ll need to replace your main water supply with rainwater for irrigation
VEGETABLE GARDEN 47 gallons

This is how much water you’ll need per week during the drier months (June, July, and August)
VEGETABLE GARDEN 564 gallons

This is the total water storage capacity you’ll need to replace your main water supply with rainwater for irrigation
LANDSCAPE PLANTS 32 gallons

This is how much water you’ll need per week during the drier months (June, July, and August)
LANDSCAPE PLANTS 384 gallons

This is the total water storage capacity you’ll need to replace your main water supply with rainwater for irrigation

Figuring out the size of your lawn in square feet can be tricky!

TIP: If you have an odd shaped lawn, split it into smaller sections and add them up for a total square foot size.

Rainwater system components

A rainwater harvesting system can be broken down into the following components. Each component has different variables as well. This information will help you understand what you may need.

Rainwater catchment area

A catchment area will almost always consist of a rooftop. Rooftops made from any material can be used to collect rainwater for non-potable use (anything except for drinking or bathing). The best rooftop material for collecting rainwater for potable use is galvanized steel or aluminum with a factory sealed coating. Copper and raw galvanized steel should not be used for potable due to the release of heavy metals into the water. Clay and concrete are OK for potable but less desirable because they hold dirt and absorb water. Asphalt shingles should not be used for potable systems because they can leach hydrocarbons.

Conveyance system

This part includes the gutters, downspouts, and all piping used for getting the rain from the rooftop to the tank. There are two types of conveyance systems for collecting rain water. One is called a "dry" pipe system and the other is called a "wet" pipe system. The dry pipe system is the simpler of the two and is used when the downspout(s) is/are close in proximity to the tank(s). it is called "dry" because there is never any water in these pipes when it's not raining. The "wet" pipe system is common with collection systems using multiple downspouts at various locations around the roof. The pipes that comprise the wet system usually run straight down from the downspouts below the ground and over to where they fill the storage tank. This allows for one location of water storage instead of one at each downspout location. It is called a "wet" system because the pipes usually keep some water in them between rains.

Storage

While we can provide and install almost every tank option available, the most commonly used tank materials are polyethylene (plastic), fiberglass, and metal water storage tanks. We usually make recommendations for which type of tank to use depending on the amount of water storage needed, space available to put the tank, accessibility to tank pad, and tank height restrictions. Metal tanks are the most aesthetically pleasing but are usually more expensive when used in smaller storage applications (10,000 gallons or less). We are an authorized dealer for "Texas Metal tanks" and "Pioneer Metal Tanks". Both are beautiful tanks and show really well on any property. The tanks we use most for systems requiring less than 6,000 are polyethylene tanks. They come in almost any color and most have 100% opaque (zero light penetration) options. Fiberglass tanks are also a great option when requiring lots of storage capacity. All three tank types are used for both potable and non-potable applications.

Pressure

Many systems can operate with the pressure of gravity utilizing a slope or difference in ground elevation (or grade). This is accomplished by setting the storage tank at a higher elevation than the receiving water. Using stored rainwater with gravity pressure alone is not always possible. When more water pressure is needed, a pump would be installed to deliver water at a higher volume rate comparable to that of the common garden hose spigot on the outside wall of a house. The pumps we most frequently use are called "on-demand" pumps, which means they run only when the water is needed. When the water is not needed, the pumps stay pressurized (with an internal pressure tank) in stand-by mode and are ready to deliver water when needed almost instantaneously. These pumps are small in size and are easy to protect from the elements using a small pump house. We also provide very small polyurethane pump houses for clients that prefer a turnkey system rather than having to build one after the installation is finished.

Filtration and disinfection

Harvested rainwater intended for potable use requires a simple filtration and disinfection process. This usually involves a sediment filter and a charcoal filter (for quality and taste) in combination with a UV light disinfection system (preventing the risk of harmful bacteria and protozoa). The water is already soft and almost never requires any additional treatment.