Overview Specifications Solutions Documentation & Tools ;


Product Features
  • Uniform distribution of air and water even in extra-long lengths
  • Standard profile of 12” (30cm)
  • Can be designed for wall-feed applications as well as center flume, front flume and Leopold Flat Bottom flume
  • Superior air and water distribution for effective backwash giving longer filter runs and lower operating costs
  • Easy handling - snaps together for quick installation

Setting the standard

Underdrains collect filtered water during the filter run, and distribute air and water during the backwash cycle. Providing cleaner filters mean longer filter runs and higher water efficiency, more product water, and less waste. This lowers your operating costs per gallon or liter of filtered water. All Leopold underdrains deliver the superior performance that has made the Leopold underdrain the industry leader.

The Leopold Type S® underdrain is an HDPE underdrain, designed for strength and corrosion resistance. It offers the most design flexibility working with the different combinations of lateral lengths as well as different flume configurations. It is ideal for installations requiring longer laterals.

The dual parallel lateral design and the water recovery channels, both developed by Leopold, give even distribution with less than +/-5% maldistribution and no dead zones.

The Type S underdrain can be specified with Leopold I.M.S.® 1000 or 200 media retainers and factory-installed on the Type S underdrain to save time at installation. The I.M.S. media retainers replace up to 14 inches (36 cm) of gravel media support allowing for the same media depth in less vertical space or longer air/water backwash.

The air flow adjustability allows for more control and saves energy and water. Air scour rate can be adjusted from 2 to 5 scfm/sq.ft. (0.6 to 1.5 m/min), enabling collapse pulse cleaning during concurrent air/water backwash with various media configurations. Air scour provides higher shear forces and cleaner media, with less wastewater generation.

Ideal for existing, older installations

The Leopold Type S underdrain is also equipped with internal baffles that can be installed to a level tolerance of ±1/4 inch. This is ideal for older installations, where construction tolerances aren't as rigid. Installation tolerances that are more forgiving also make for simpler installations and lower filter construction costs.

In addition, the Grout-Tite® Bridge prevents grout from entering the flume, so there's no costly cleanup.



General Information
Type S underdrain
Potable Water, Wastewater, Desalination Pretreatment
Underdrain type
Dual parallel lateral
Types of backwash suitable
Water only, sequential air followed by water, concurrent air/water and sustained air/water
Standards met
NSF 60, British DWI, French
Flume types suitable
Flat Bottom Flume, Front Flume, Center Flume, H-Flume
Construction type
New or existing regardless of current underdrain type
Media retainer compatibility
Gravel, I.M.S 200 media retainer, I.M.S 1000 media retainer
System Components
Type S underdrain
Nominal dimensions
48" long x 11" wide x 12" high (1.2 m long x 0.28 m wide x 0.3 m high)
System components material
High Density Polyethylene (HDPE)
25 pounds (11 kilograms) approximate
Air flow range
2 - 6 scfm/sf (40 -110 m/hr)
Water flow
Up to 30 gpm/sf (75 m/hr)
Maximum lateral length
End feed 48 feet (14.6 m), Center feed 96 feet (29 m)
Water mal-distribution
Less than +/- 5%
Level tolerance
+/- 1/4" (6 mm)
Orifice spacing
2" (50 mm)
Orifice recessed for gravel
Yes, to reduce gravel plugging
Secondary baffles
Water recovery channel
Yes, one in the center
Underdrain block connection
Bell and Spigot
Technical Details
Type S underdrain
Weight (lbs./sq. ft)
Approximatly 6.3
Weight (kg/m2)
Standard block dimensions (in / ft)
11" wide x 6" high x up to 38' long
Standard block dimensions (cm / m)
27cm wide x 15.2cm high x up to 11.58m long
Installed structural capacity (kg/m2)
7000 (Minimum evenly distributed load)
Burst strength (psi)
Burst strength (KPa)
Lateral Length
Type S underdrain
Height (inches)
Height (cm)
Center flume (feet)
Center flume (meters)
Front flume (feet)
Front flume (meters)
Wall feed/H flume (feet)
Wall feed/H flume (meters)
Leopold flat bottom (feet)
Leopold flat bottom (meters)
Blower Casing
Type S underdrain
Extruded High Impact Rigid PVC
Documentation & Tools

Documentation & Tools




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