Rainwater Catchment Systems

Using captured rainwater for watering your garden or lawn is a great way to reduce potable (drinking) water use in your home.
Photo credit: Grand Canyon NPS

While rainwater harvesting systems vary in complexity and sophistication, you can create a pretty simple system by yourself using a rain barrel. Rain barrel prices vary, but you should be able to buy a good one for under $100.

Typically, a simple rain barrel system is used for irrigation purposes. However, rainwater catchment systems can be used for other purposes, such as flushing toilets, and in rare cases, for drinking water.

To set up a rainwater catchment system that uses the water for flushing toilets (or other indoor non-potable uses), you will need a more complex system. You will need to hire an experienced plumber or contractor to install the system.

Rain Barrels

In a simple residential storage methodology for rainwater collection, a 55 or 90 gallon food-grade container or barrel is utilized to collect rainwater from a home's roof via the gutter and downspout system. Rain barrel prices vary, but you should be able to buy a good one for under $100.

The most common (and easily implemented) use for this stored water is for landscape and plant irrigation. The collection container or barrel should be secured and located on a firm, level surface. It should have a lid and fine mesh covering on all openings to prevent mosquitoes and debris from entering. Additionally, the barrel should have an overflow to a safe discharge point.

You can use these steps to collect and filter rainwater from your gutter in a rain barrel. Then, you can use the collected rainwater to water your plants and grass.

Alternatively, you can hire a professional with rainwater catchment system design and implementation experience to set up your rain barrel for you.

Free LEED v4 Green Associate Practice ExamRainwater Harvesting Systems

According to Harvest H2O, here are three main types of technologies found in more complex rainwater harvesting systems:

1) Pressure Tanks: Pressure tanks are a widely available, proven technology. It typically holds about 35 gallons of filtered water. The tank contains a bladder, which provides water pressure. When the pressure in the bladder decreases, the pump turns on and refills it with water. This requires a pressure-sensitive pump to turn off the water when the bladder reaches a certain pressure.

2) Pressure Sensitive Pumps: This pump senses decreased pressure, and then turns on to refill the water line and restore its pressure. This is a newer, more expensive technology, but is easy to install and maintain.

3) Inline Pump Controller: This controller also senses decreased pressure and automatically turns on to refill the water line, and can be used as an alternative to pressure sensitive pumps. They can be installed directly in the existing water pump and line and are cheaper, but are not as commercially available.

Systems vary in price based on the technologies chosen and the labor costs. Harvest H20 estimates that the pressure tank costs about $270, pressure sensitive pumps cost $595, and inline pump controllers cost around $270.

Rainwater Harvesting and LEED

Rainwater harvesting could contribute to the following credits in LEED for New Construction 2009:

Sustainable Sites (SS) Credit 6.2: Stormwater Design - Quantity Control (1 point)
This credit awards one point for managing stormwater runoff so that it reduces the amount of pollutants in the water shed. Rainwater recycling is specifically listed by USGBC as a potential strategy for this credit.

• Water Efficiency (WE) Prerequisite 1: Water Use Reduction (0 points)
This prerequisite requires that the LEED project use 20% less water than the baseline calculation. Since rainwater can be reused, such as for flushing toilets, treatment systems could contribute to this prerequisite.

• WE Credit 1: Water Efficient Landscaping (2-4 points).
This credit awards 2 points for reducing irrigation needs by 50% and 4 points for no potable water use or irrigation. Rainwater harvesting could make up some or all of the site’s water needs for irrigation, so it can contribute to this credit.

• WE Credit 2: Innovative Wastewater Technologies (2 points)
Credit 2 awards 2 points for reducing potable water use for sewage conveyance by 50%, or for treating 50% of of wastewater on-site to tertiary standards. Stormwater may be used for sewage conveyance if it is treated with a natural or mechanical system, so rainwater collection systems may contribute to this credit.

• WE Credit 3: Water Use Reduction (2-4 points)
This credit is the same as WE Prerequisite 1, except the required percentage of water use reduction is higher. Projects can earn 2 points for 30% water reduction, 3 points for 35%, or 4 points for 40%.

Can I Drink Rainwater?

Rainwater must be treated before it is considered potable (or drinkable). Typically, building a rainwater treatment plant on site is too expensive to make it worthwhile. Also, because of the treatment process, treated rainwater usually smells like chlorine, which makes people think it is unsafe to drink. Despite these setbacks, it can and has been done.

A treatment system works by first collecting rainwater above or below ground in a cistern. Then, it is disinfected, either with chemicals, such as chlorine or zone, or light (ultra violet rays).

If treating rainwater to drinking standards on site, it is important to consider the building’s roof. Water that comes off of a metal, ceramic or slater roof is easier to treat than asphalt shingles or roofing membranes, which leak more chemical modules. Additionally, the roof should be sloped, which is better for harvesting rainwater than a flat roof.

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