The following tables indicate the maximum lengths various sizes of troughs can span without additional supports when fully loaded.  Most troughs can carry additional weight such as piping, or equipment suspended from the troughs in addition to the dead weight of the trough plus the weight of water filled to the top of trough. The following calculation is an example of such a condition.

For a printable PDF version click the file below:

 Tensile Strength                                               8,700psi min ASTM D638
 Flexural Strength                                             18,000psi min ASTM D790
 Flexural Modulus                                             1.0 x 106 psi min ASTM D790
 Compressive Strength                                    11,000psi min ASTM D695
 Average Coefficient of Thermal Expansion   10.5 x 10-6 ASTM D696
 Water Absorption % 24 hours                       .10% ASTM D570

Cantilever side wall support for circular clarifier trough. Typical support consists of 18" FRP Beams & 6" x 6" x 1/2" angle knee brace

Flat Bottom Troughs

Rocklin, CA troughs supported on steel beams. 12" wide x 18" deep trough spanning 24'0". Ends not fixed.


Curved Trough with block out for drop out trough. Shows tongue end and integral recess for attachment of drop out trough.

Typical Weir Configurations Launder Troughs

Chalk Bluff, NV trough with blind end and wall saddle mount

Reviewing the above and the table on the next page (and tables on pages 13 to 18) you can see that Glass·Steel® Trough designs have no significant competition.  Yet competitors troughs are specified and sold every day.  This is typically done by “bundling” by the local reps of clarifiers, filters, and other equipment to prevent the use of competitors products.  The only way around this is to specify this design or equal.

The difficulty is finding an equal to this product…….

Physical Properties

Typical Weir & Baffle Configurations for Clarifiers


Curved wall mounted trough, shows groove end of tongue & groove

Note: All connections shown are typical of both round & square bottom troughs.

Other special configurations can also be made

Fiberglass Composite Troughs

Trough Wall Connection Water Stop Integral Anchor

Typical End Wall Connections

Straight Trough

Top trough shows tongue end of tongue & groove, bottom trough shows square end for saddle mount

Section A-A

With Blind End

Separate Saddle Connection Square Bottom Trough Shown


Curved wall mounted trough with drop out box

*Assumes 3/16 inch max deflection allowed.  On spans over 10 to 15 ft, depending on cross section, competitors must support the trough at mid span or provide multiple supports, or use design “stiffeners” applied to the outside of the trough to meet this criteria. Glass-Steel®  troughs do not.  Competitors designs must be limited to certain narrow and deep cross sections to allow use of their design.  Glass-Steel® troughs have no cross section design limitations like our competitors.  Ask our competitors for their published span values that do not require additional stiffeners mounted to the product, what their maxium span is for flat bottom wide troughs, what unsupported spans they are capable of without structural supports,  lateral supports, and without stiffeners?  Can other equipment be supported from their troughs?  Why do they need spreader bars?  Honest answers will lead you to the conclusion: Glass-Steel® Troughs have no competition.
**Round bottom tough both ends fixed.

Typical Tongue & Groove Joint

Height of 1-1/2” wall troughs is limited to 42” inside depth per the following formula.  For deeper troughs we increase the wall thickness to accommodate the depth.  This also increases the physical properties of the trough.

Drop out Trough Integral end mounts

Section B-B

Open End

Hanger saddle support for support from above. Typical support consists of 4" x 4" x 1/2" FRP angle and 8" x 2-3/16" x 1/4" FRP channel

Glass-Steel, Inc. manufactures a proprietary system of composite effluent troughs for water collection in the water/wastewater applications.  Troughs are typically used in clarifiers (both circular and rectangular), grit collectors, sedimentation basins, thickeners, filter systems, etc.  Glass-Steel, Inc.’s composite troughs offer features and benefits not available in pre-cast or cast in place concrete troughs, aluminum troughs, stainless steel troughs, galvanized or painted steel troughs, or conventional fiberglass troughs.

Glass-Steel, Inc. composite toughs utilize a glass reinforced fiberglass skin on the inner and outer surfaces with a polymer concrete core.  Typically our trough walls are 1-1/2” thick with 1/8” fiberglass skins although different thickness can be produced.  Because the entire system is made with Isophthalic polyester resin the composite is impermeable to water absorption, the sandwich type construction acts as a monolithic unit, and all components have the same coefficient of thermal expansion (we can also make vinylester, epoxy, or other resin systems).  

Because of the mass of the composite troughs we do not need any spreader devices or exterior bracing of any kind.  Our mass also creates a moment of inertia that allows us to clear span distances of over 14’ on our shallowest & widest trough to over 40’0” on our narrowest & deepest trough without the need for intermediate supports or lateral stabilizers.  This means that all of our troughs are easily walk able for maintenance purposes and they require less or no additional structural supports.  In the instances as in rectangular clarifiers where troughs can be over 50’ in length we do require an end support and at least one intermediate support.

Glass-Steel, Inc. composite troughs are competitive with all other conventional type troughs on a dollar to dollar per foot cost basis.  They are less than half the cost of stainless, far less than aluminum, less than or equal to most conventional fiberglass troughs.  Also the benefits of longer clear span capability, no internal spreaders, smooth uninterrupted inside & outside surfaces, easier installation, and less maintenance and you have an economically superior system to any other trough system available.

The following are drawings and load tables indication some standard details and attachment methods for some standard sizes and configurations of troughs.  Troughs are furnished in round bottom or square bottom configurations and can be furnished as straight or curved sections.  Glass-Steel, Inc. also furnished custom trough with tapered sides and or bottoms, etc.  Our side mount troughs eliminate the expense of forming and pouring in place concrete extended wall troughs.  Glass-Steel, Inc. also custom builds drop troughs and other accessories.

Integral End Wall Connection Round Bottom Shown Square Bottom Similar

Angle connection to support beam under trough

Typical support consists of 4" x 4" x 1/2" FRP angle and 8" x 2-3/16" x 1/4" FRP channel

Note: All braces occur at trough splices.

           All typical wall connections are considered fixed connections.

           All intermediate connections at supports are considered not fixed except side mount trough, which is fully supported on one side.


Trough Wall Connection Anchor Bolted

Typical Trough Sections

industrial & municipal fiberglass fabrication

Rocklin, CA troughs fixed one end supported by steel beam on other end.

Fiberglass Composite Trough Configurations


Curved wall mounted trough, with hole for drop out box

Glass-Steel, Inc.

Call now: 1.281.572.2211

Curved Trough

Trough shows groove end of tongue & groove


Curved wall mounted trough installed with weirs & baffles

Chalk Bluff, NV troughs anchor bolted to effluent end

GLASS•STEEL® TROUGH DESIGNS:


  •  MEET OR EXCEED ALL AWWA F101-07 DESIGN REQUIREMENTS

  •  SUPERIOR STRUCTURAL PROPERTIES VS ALL OTHER FRP TROUGHS   (see table below and tables at the end of this data)

  •  LATERAL SUPPORTS ARE NEVER REQUIRED

  •  SPREADER BARS ARE NEVER REQUIRED

  •  DESIGNS AVAILABLE TO CLEAR SPAN 50 FT

  •  AVAILABLE IN MULTIPLE CROSS SECTION SHAPES

  •  LOWEST LIFETIME COST VS STEEL, ALUMINUM, STAINLESS

  •  LOWEST INSTALLED LABOR COST

  •  LOWEST MAINTENANCE COST, LONGEST INSTALLED LIFE

  •  STANDARD 5 YEAR WARRANTY, 10 YR AVAIL ON REQUEST.

  •  EACH GLASS·STEEL INC. TROUGH IS CUSTOMER SPECIFIED 

  •  IN MOST INSTALLATIONS GLASS·STEEL® TROUGHS CAN BE USED AS SUPPORT  FOR OTHER EQUIPMENT

  • AFTER INSTALLATION MAINTENANCE PERSONELL CAN WALK IN A   GLASS-STEEL® TROUGH W/O A TRIP HAZARD

  •  POLYMER CONCRETE CORE HAS SUPERIOR STRUCTURAL PROPERTIES AND PERFORMANCE vs. CONCRETE IN WATER AND WWTP ENVIRONS

  •  NSF61 DESIGNS AVAILABLE