Finding Unused Water in New Places: Using Condensate for Irrigation
Designing commercial landscape projects in Texas requires expanding and flexible strategies for irrigation. Increasing growth and the lack of a steady supply of water in Texas requires landscape architects and our clients to explore new approaches every day in design. The collection of air conditioner condensate water is one solution to insure a continual supply of irrigation water for Texas’ commercial landscapes.
The basis for much of Texas real estate development is a plentiful supply of potable water. The eastern half of the state’s population of 20 million has been growing abundantly, especially when compared with the drier, less populated western half. While Texas’ population has been growing steadily and quickly, our water supply has not.
Much of the source of municipal water is from man-made reservoirs, adequate river and creek flow, and more frequently, wells. Some cities are almost entirely dependent on the water well capacity from vast aquifer supplies. San Antonio is one such example. The city’s population of 1.4 million consumes 67.4 billion gallons per year of water, which equates to 131 gallons per person per day. This number however, is very competitive compared to other cities in Texas.
Average GPCD (gallons per capita daily) statistics*:
San Antonio: 131 Austin: 124 Dallas: 190 Houston: 147 Corpus Christi: 122 Fort Worth: 140 *The data has been primarily collected through the Texas Water Development Board’s annual survey of water use, 2013.
The problem with San Antonio is the source – it’s predominantly well water from the Edwards Aquifer. When ground water is plentiful (during good rainfall/recharge years) there are no major problems. But in drought years like 2011, water restrictions can greatly cut back on (or eliminate) landscape irrigation. Watering every 2 weeks in Stage 3 or 4 is just not enough to sustain landscapes, or even native trees. In central Texas, the shallow soil depths, high temperatures, and wind can remove soil moisture quickly.
Condensate water captured from building air conditioning systems is one solution our firm used in two apartment projects at La Cantera for USAA Real Estate Company. The first, The Residences at La Cantera, is a 320 unit community, from which approximately 4500 gallons per day is produced from air conditioner systems in summer months. That water is collected and used to irrigate the park adjacent to the complexes.
The first phase project (The Residences) was piped and plumbed internally to collect condensate from individual apartment units, along with the other traditional infrastructure. This system must be developed and designed from the beginning to be cost effective and feasible. Each apartment unit produces about 13 gallons per day in a typical summer day. When multiplied and collected throughout the complex, including common spaces and management offices, the total yield makes the quantities hard to believe. The 4500 gallons of water produced daily have previously been discarded as “waste” since they are a by-product of air conditioning and not useable for any other purpose. But now, this condensate water is collected and stored, and can serve as the building or adjacent site irrigation system supply.
This is important to water customers in San Antonio to understand, since water restrictions can potentially reduce available irrigation drastically. The chart below shows the demand for a typical multi-family project landscape, as well as the condensate supply produced in a typical project. Note: the highest condensate supply coincides with the highest months of irrigation need.
Chart of landscape water need vs. amount per month supplied by condensate.
The graphic illustrates the comparison between the irrigation demand and the flow of water from a combination condensate and rainwater collection system. This type of system was designed for the Phase Two apartment project for La Cantera, with the collaboration of the Architect, MEP, Civil, Landscape Architect, Irrigation, and Water Feature consultant. For this system, all units from the building supply condensate water, and one-third of the roof provides rainwater.
(The above Illustration shows the collection points for condensate)
The result of this combination - ALL the irrigation water for this project can be supplied by this project, regardless of water restriction status in San Antonio. This saves the landscape from highly restrictive schedules and reduced/eliminated irrigation as well as savings on SAWS (San Antonio Water System) water bills. The average cost of irrigation water for a project such as this would be approximately $1,344 per month in the summer. The average savings over a year’s time would equal approximately $10,000.
In summary, this approach will allow building managers to use “free” irrigation water, regardless of the regulatory environment.
This is one of the most sustainable elements that is easily incorporated into building and landscape design for today’s increasingly water efficient landscapes.