by Michael Igo, Affiliate ASLA, PE, LEED AP
Everyone loves fountains. They provide a three-dimensional sensory experience in any urban landscape. However, they are complex architectural elements that generally require a multidisciplinary effort to bring into reality. To achieve the visual and aural benefits they provide to a site, water quantity and quality must be managed for both interactive and non-interactive water features.
We often find that there is reluctance amongst site owners and operators to maintain architectural fountains. Dealing with chemicals, biofilm scrubbing, strainer cleaning, pump control programming, and winterization requires either commitment by on-site staff to be trained and dedicated to these water features or hiring an outside third-party to manage them remotely and provide frequent site visits. Similar to swimming pools, there needs to be a frank conversation with the owner to let them know what they are inheriting for a system. Where allowed by law, often owners will opt for a “pass-through” or “once-through” fountain where municipal domestic water, already chlorinated, passes through the fountain and drains away to a sanitary or storm sewer—saving on the cost of pumping and sanitation of recycling water.
The problem is that pass-through urban architectural fountains and splash decks waste substantial amounts of drinking water. We still see pass-through urban architectural fountains in use in older Northeast cities where no one considered the amount of water waste 50 – 100 years ago.
To put in perspective the amount of water waste, let’s say that a pass-through fountain in a city runs 24 hours per day. In each hour there are 60 minutes, so in 24 hours there are 24 x 60 = 1,440 minutes. For every 1 gallon per minute of flow, 1,440 gallons of water go down the drain EVERY DAY. However, 1 gallon per minute is a relatively small fountain. An example below of a seemingly benign fountain shows just how much flow is needed to achieve the effects desired:
This fountain in Massachusetts at a prominent city square is a pass-through fountain that flows 10 gallons per minute to achieve the desired effect. Every day, this fountain wastes 10 gallons per minute x 1,440 minutes per day = 14,400 gallons per day to the sanitary sewer system! And this one is small—this author has seen pass-through fountains on the order of 50 – 100 gpm (72,000 to 144,000 gallons per day).
Depending on the size of the planted landscape where small architectural fountains are situated, pass-through systems provide an excellent opportunity to capture water for irrigation that would otherwise be wasted. If properly managed, 14,400 gallons per day from the fountain can irrigate up to 100,000 square feet of lawn in the same Massachusetts location in the peak of the summer. These are small fountains in the landscape architecture world and, clearly, this is a substantial amount of water wasted that needs further examination in retrofitted and new landscapes.
You may be thinking: let’s design a recirculating fountain and minimize the waste; why consider a pass-through fountain at all? Any landscape architect that has worked with architectural water fountains and splash pads with a consultant or manufacturer knows that recirculating systems have complicated mechanical systems that require, at least some of the time, for a designated maintenance person to handle caustic chemicals like chlorine and bromine. While there are safer alternatives like ultraviolet (UV) light sterilization and ozone injection, these alternatives do not provide residual sanitation if these dispensation systems stop. In other words, if the UV or ozone systems stop working, the water will immediately begin to foul. With chlorine and bromine, these chemicals continue to sanitize water for a longer period of time in the event these systems go down or travel long distances. Our municipal domestic water supplies carry a small amount of chlorine residual in order to continue to sanitize our water from the treatment plant, through miles of underground pipe, and to our home faucets. Pass-through fountains that use municipal domestic water are already chlorinated and safe for drinking—making them popular for some splash pads, spray decks, and non-interactive water features.
As with any design choice, there are pros and cons with pass-through fountain water capture for irrigation.
- A pass-through fountain eliminates a considerable amount of labor and maintenance versus a recirculating fountain:
- Simplifying controls
- Eliminating the handling of dangerous chemicals
- Eliminating breakdown and repair of complicated mechanical systems
- Providing a simple system that public and private grounds staff may not have the bandwidth or experience to deal with these systems
- Often this equipment is located in confined or restricted areas
- A pass-through fountain can generate a lot of water that can be reused for irrigation.
- Municipal domestic water is already chlorinated with residual disinfection after dispensed from the fountain
- The municipal domestic water will continue to stay residually chlorinated in the fountain and potential recapture tank for reuse in irrigation for up to a day or more depending on initial chlorination levels.
- Irrigation uses domestic water straight from water mains anyway, typically.
- Pass-through fountains with recapture potential can be cost-effective solutions versus recirculating systems
- Additional filtration and UV sterilization could be added to an irrigation system for splash pads and spray decks (limited interactive water features)
- Not all fountains and water features would be candidates for recapture, including:
- Large architectural fountains (generating too much water)
- Water parks and swimming pools
- Pass-through fountain water generation should closely match irrigation demand to be effective
- If a 10 gallon per minute fountain can irrigate 100,000 square feet of lawn, then it may not be a good choice for either a 10,000 square foot or 1,000,000 square foot landscape, for example.
- Requires more irrigation maintenance and technical acumen
- We are trading the potentially hazardous maintenance of recirculating fountains for increased controls and water movement with a harvested water irrigation system
- Local laws may restrict the use of such systems.
Higher-end commercial irrigation systems can control, program, and time solenoid valves for pass-through water features to limit the amount of time they are running in order to balance the capture potential versus the landscape. Instead of running 24 hours a day, a pass-through water feature can be programmed to only run 16 hours per day (cutting the water pass-through by 33%) and allowing for irrigation to take place in the remaining 8-hour period overnight—allowing the recapture tank to empty and start the process anew the next day. Combined with smart irrigation controls that irrigate based on weather and climate data feedback (such as wind and rain sensors to suspend fountain operation), a fully integrated and unified fountain/irrigation system can be achievable.
While not a traditional means of capturing water for irrigation, fountain water waste can be a means of “having our cake and eating it, too.” We can have the beauty and serenity that a water feature provides for a landscape while also irrigating the planted landscape in a responsible way that considers water, costs, and labor resources—a fully sustainable approach.
Michael Igo, Affiliate ASLA, PE, LEED AP, founded Aqueous Consultants, LLC, in 2014 with nearly 25 years of engineering experience in water resources. As a self-proclaimed “right-brained engineer,” his love of science and graphics resonates with clients and other design professionals. His unique education degrees in Aerospace and Civil Engineering lends to design of both mechanical and civil engineering systems found in landscape water projects. Mike has documented hundreds of credits for LEED, created Aqueous’ computer climate model, and has been honored by the ASCE for his sustainability research. He has also presented at the ASLA Conference on Landscape Architecture and is chair of the ASLA Water Conservation Professional Practice Network (PPN).
Mike will be presenting Water or Waste? Adaptive Approaches to Water Resources Management and leading the Water Conservation PPN Meeting with Bryce Carnehl, Affiliate ASLA, at the ASLA 2023 Conference on Landscape Architecture in Minneapolis later this month.