Tennis Technology

The International Tennis Federation (ITF) approved a two-year rule change to test different types of tennis balls for different court surfaces. 

Change in the tennis court construction industry doesn't happen all that often. So when it does it's BIG news. Many people don't realize it, but there's a quiet revolution underfoot with today's soft courts. The last time something this big occurred was when the British company En Tout Cas developed the fast-dry court in 1909. But as dramatic as this change is, most people won't ever see it because it's taking place below the surface of fast-dry courts. What's new is that today's courts are being watered from underneath. This changes a lot of things, not the least of which is the way fast dry courts play.

The concept of watering from below was introduced to tennis in the early 1980's. Today, industry suppliers of fast-dry material estimate that between one third and one half of all new fast-dry courts in the United States are being constructed with subsurface irrigation systems. This trend is expected to continue with hundreds of new subsurface irrigated courts being constructed each year.

A subsurface irrigated tennis court is nothing more than a tennis court which is watered from below the surface of the court rather than from above as with a conventional sprinkler system. Moisture that is introduced into the base material of a court will naturally rise up to the fast-dry material on top as a result of a geotechnical phenomenon know as capillary action. This moisture is what binds the surface of a fast-dry court together and makes it playable. Over time, the moisture evaporates as a result of temperature, humidity and wind.

The major difference between a subsurface irrigated court and an above-ground irrigated court is how the moisture in the surface material is re-charged as it evaporates. With above-ground systems, the court surface must be saturated and the water allowed to seep into the base material. This makes the court unplayable for a period of time. It also means that the court is continuously changing in its moisture content as it dries out, which affects the playing characteristics of the surface. With subsurface systems, the base material can be wetted either continuously through the use of a subsurface reservoir system or intermittently through the use of an electronically controlled timer which turns a water source on and off. This allows the surface moisture content to be maintained easily without having to saturate the playing surface.

Today, there are four major tennis court subsurface irrigation systems that dominate the national market place. They are Cal-Cap by Calico Racquet Courts, Morehead City, North Carolina; Hedrocourt by Lee Tennis Products, ( Charlottesville, Virginia; HydroGrid by HydroGrid Tennis, St. Petersburg, Florida; and AquaGrid by Har-Tru Corp., Hagerstown, Maryland. While each of the systems provide water below the surface of the court, their water conveyance systems and court construction methods are not the same. Indeed, each system uses patented technology.

Despite the differences between the four major systems, they're all dependent upon the capillary action of water as it moves up toward the court surface to maintain moisture in the fast-dry material. Moreover, they all utilize roughly the same amount of water to irrigate a fast-dry court since water consumption is not a function of subsurface irrigation technology, but rather a function of evaporation at the surface due to climatic conditions. In fact, whether a court is surface or subsurface irrigated, the amount of water needed will vary greatly depending upon the geographic location of the court, the local weather conditions and the specific microclimate of the court itself.

What Subsurface Irrigation Can Do for You?

Watering a fast-dry court from below offers some unique advantages to tennis facility owners and managers. First of all, subsurface irrigation can save a significant amount of cost in terms of water usage. Since the water is applied from below at a rate equal to surface evaporation, there is no waste due to overspray, run-off and wind loss associated with conventional above-ground irrigation systems. Water savings of as much as 85% are not unusual in extreme climates.

Maintaining a consistently moist fast-dry surface through subsurface irrigation also preserves a significant amount of surface material typically lost due to wind and storm water erosion. Again, this translates into an annual savings on material costs.

Subsurface irrigation significantly reduces the need for court rolling. While an above-ground irrigated court requires rolling almost daily, subsurface irrigated courts typically require rolling only two or three times a month or less depending on usage. This translates into significantly reduced maintenance costs.

Perhaps most important is the fact that subsurface irrigation eliminates the need for "down time" due to watering and rolling. Since a subsurface irrigated court is ready to use at any time of the day, the revenue potential of a court is substantially increased. If you own a private court, there's the luxury of being able to play virtually on a whim, since there's no need to get the court ready before play.

Initial Start-up Difficulties

Despite the growing industry enthusiasm about subsurface systems, its important to realize that there can be some initial difficulties with these types of courts. These drawbacks are not so much shortcomings of the technology as they are failures to fully understand it or properly use it. For instance, a subsurface irrigated court surface plays differently than a conventional fast-dry court The perceived differences may be due to the fact that subsurface systems often use a coarser fast dry surface material and the surface is "wetter." These two differences can significantly affect ball slide and bounce as well as player footing.

While these differences in no way detract from the game, players are keenly aware of them. In cases where clubs with conventional fast-dry courts have added subsurface irrigated courts, players have complained not so much about one type of court as they have about the fact that there are differences in play between the two types of fast-dry courts, requiring adjustments to their game. The reality is that most players are used to playing on a dried out fast-dry court. Without question, subsurface irrigated courts are a different surface. Owners should understand that they are purchasing a new type of court.

The change over to subsurface irrigated courts is often a difficult learning curve for the court maintainers as well. They have grown comfortable with the idiosyncrasies of conventional fast-dry courts and often have difficulty adjusting to a different situation. While this problem is easily corrected with time and education, unrealistic expectations can make for unsatisfied and impatient customers. Increased and consistent moisture content in the surface can lead to increased algae, fungus or mildew problems on the court surface. This is one of the hazards of subsurface irrigation, but it can be ameliorated by adjusting the surface moisture content or by other herbicidal methods.

Not to be forgotten is the issue of increased construction costs associated with subsurface irrigated courts. A subsurface irrigation system, depending on which system you purchase, can increase court costs on average between $3,000 and $8,000. While they are indeed more expensive, their greater water efficiency, reduced maintenance and increased usability allow for a quick pay-back with a relatively short period of time. Some clubs, for example, have been able to recoup the additional costs within one season simply because of the increased court access. Most facilities will see a pay-back within two to five years, depending upon usage and local market conditions.

What to Look for When Buying a Subsurface System

Before making the decision to construct a subsurface irrigated court, it's important that owners fully understand what it is they are buying. A subsurface court is not a "no maintenance" court. The court may need to be rolled less, but it will still need to be swept, divots will need to be repaired, and if you live in an area where them are freezing conditions, the court will need to be winterized. Furthermore, its critical that owners insist upon some form of service after installation to ensure proper adjustment of the system and proper instruction to maintenance personnel. This may cost more, but it's well worth the extra expense. No matter how well a court is constructed it will only perform as well as it is maintained.

Also, be sure to comparison shop. Since no two systems are exactly alike, speak to owners of the same systems you are considering. Ask the tough questions about water consumption savings, contractor service after the court was completed and if there are any on-going problems. Look at courts that are at least two years old so you can evaluate their performance over multiple seasons. Make sure you feel comfortable with the mechanical systems that are proposed with the court that you may purchase. If possible, schedule a game on the court to get a feel for how it plays.

Finally, don't make your decision based on cost alone. As with any new technology, there's always those contractors who will try to produce a cheap knock-off for a low price. As cliche as it may sound, you get what you pay for. Without question, a properly constructed subsurface irrigated fast-dry tennis court that utilizes a reputable system and is installed by a reputable contractor will save you valuable time and money over the long term. The more important question should be whether or not you are prepared to make the leap into the future.

by Andrew R. Lavallee, ASLA and Sheldon Westervelt, P.E.