Products, Vendors, CAD Files, Spec Sheets and More...
Sign up for LAWeekly newsletter
An effective drainage system is the first step to a safe and healthy playing surface. Proper drainage keeps fields dry and playable on rainy days and cuts down on repair costs linked to turf damage and disease. With that in mind, Turf Talk is taking a look at what goes into installing a successful drainage system for both synthetic and natural surfaces.
In most natural turf situations, it is best to install drainage vertically. A four-inch wide trench is ideal both for performance and ease of installation. It produces little spoil and results in excellent drainage because it takes advantage of the vertical footprint.
For synthetic turf, trenching is not necessary. It is best to install the irrigation system on a flat uniform surface before the field is installed. Collector lines can be positioned horizontally directly on the compacted base, or on top of the geotextile soil separator if one is used.
Crowned or sloped fields: If the surface of the field has a consistent slope (greater than .5%), it is advised that the collector lines be placed such that they intersect the water flow direction. Placing the lines at a 90 degree angle to the flow direction and running toward the end zone is usually not the best policy.
The resulting lines would be too long and, in order to maintain fall, excessively deep. A 45 degree angle running toward the sidelines works well because it allows the lines to maintain grade while also intercepting the direction of surface water flow. The resulting herringbone pattern complements the existing field contour, providing effective drainage as well as an uncomplicated installation.
Flat or irregular fields: If the field is flat, or has less than a .5% slope from the center, then a parallel drainage pattern may be appropriate. Since the water will basically stand on the surface of a flat field, there is no advantage in attempting to place drainage lines in the flow path. Collectors could run toward the sidelines or the center of the field. On flat fields, proper grade needs to be maintained by increasing the depth of the trench.
Synthetic turf fields typically have a consistent center to sideline slope. As above, collector lines should be placed such that they intersect the water flow direction. This drainage pattern should extend all the way to the edge of the synthetic turf so it will include the intensively used sideline area. Transport lines should be located at the edges of the field.
The drainage pattern should extend 10?EUR??,,????'??? to 15?EUR??,,????'??? beyond the field to include the intensively used sideline area. Six-inch irrigation lines are ideal for these on-field collectors. It is also advisable to run 18-inch lines along the sides of the field or all around the field. These lines will collect water that might run toward the field from the outside and provides supplemental drainage to the sidelines.
Placing collector lines 10 feet apart, outlet to outlet on a natural grass field, provides a good reaction time and uniform drainage performance. A field employing 15-foot spacing provides an adequate system, but placing lines 20 feet apart will require a longer waiting period before use after a rainfall.
The coarse sand and rock used in synthetic turf fields is capable of absorbing substantial amounts of water. Consequently, it is acceptable to allow more time for desaturating the base of a synthetic field than a natural turf field and as a result, collectors can be spaced farther apart. Placing collector lines 15 feet apart, outlet to outlet, provides excellent reaction time and uniform drainage performance. Twenty feet apart provides an adequate system. A field employing 25 foot spacings will require significantly longer to drain after a rainfall event. It would be unwise to space them farther apart because allowing water to set on the compacted base for prolonged periods of time will soften the sub-grade and destabilize the base.
The five factors to take into account when determining the line spacing under a synthetic surface:
The three factors to take into account when determining the line spacing under a natural surface: Anticipated schedule Local rainfall events Project budget
Due to strength and flow rate requirements, a smooth wall pipe makes for the best transport system. PVC pipe is commonly used. A standard PVC elbow or T can be slipped over most connectors.
To design a transport system it is necessary to calculate the total drainage system capacity. For an example, let?EUR??,,????'???s assume 40 lines of 6?EUR??,,????'?? pipe are used in an area 210 feet by 400 feet. If the field is crowned and laid out in a herringbone pattern, these lines will empty into the transport system on both sides of the field. So effectively, there are 80 collector lines. If each carried 17 gallons per minute, these 80 lines could deliver 1,360 gallons a minute or 81,600 gallons an hour. Sideline drains could increase that amount. Leaving the site, this would require a minimum of one 12-inch or two 8-inch PVC pipes.
It is common for any surface to step up the size of the transport pipes as they proceed along the perimeter trench. A 4-inch PVC can carry 112 gallons of water a minute (1% slope, no head pressure) so it would be adequate for handling water from the first 6 or 7 collector lines. A 6-inch PVC can carry 327 gallons of water a minute (1% slope, no head pressure) so it would be suitable for carrying the previously collected water plus the water from the next 13 collector lines. An 8-inch PVC can carry 704 gallons of water a minute ( 1% slope, no head pressure) so it could do the job the rest of the way down the field. Clean, very coarse sand acts as an excellent filter, dramatically extending the life expectancy of the system.
Many synthetic turf installers and designers call for a perimeter trench containing a perforated transport pipe. Because of strength and flow rate requirements, a smooth wall pipe makes for the best transport pipe. Like with natural surfaces, when designing an adequate transport system it is necessary to first calculate the total drainage system capacity.
The best systems employ an 18-inch line installed vertically along each side of the field. The 6-inch collector lines connect directly to these 18-inch sideline collectors, which periodically empty into solid PVC transport pipes. Sideline catch basins add additional drainage capacity.
Backfill material may be the single most important factor affecting the longevity of a drainage system of both natural and synthetic surfaces. Sand can function as a filtration device, removing silt and clay particles, while allowing water to pass through. Clay or silt soil excavated from the trenches should be removed from the site. Trenches should then be backfilled with a clean, very coarse sand, nearly to the surface. To eliminate voids in the backfill, trenches can be jetted with water or settled with a vibratory compactor after all connections have been made.
For a synthetic surface, a two-inch band of very coarse sand should be installed covering the top and sides of each collector line. This sand backfill could be eliminated if the select aggregate is free from silt and clay, but this is seldom the case.
Francisco Uviña, University of New Mexico
Hardscape Oasis in Litchfield Park
Ash Nochian, Ph.D. Landscape Architect
November 12th, 2025
Sign up to receive Landscape Architect and Specifier News Magazine, LA Weekly and More...
Invalid Verification Code
Please enter the Verification Code below
You are now subcribed to LASN. You can also search and download CAD files and spec sheets from LADetails.