Drainage Grates Inlets, Frames and Curb Inlets 
Drainage grates are designed to accept water and can be round, square, or rectangular. It is typically sold with a frame, curb inlet frame, monument box, or bridge drain. Some markets call these slotted covers.
Access Covers, Grates and Frames | INLETS & STORM SEWERS 
Grating Thai produces and offers a variety of cast iron drain bridge scuppers. the bridge scupper street and construction castings to meet ASTM and AASHTO criteria. In addition, our castings meet federal and state DOT specifications; and other county, city or local standards. Customer choices are typically based on shape, size, load rating, material type, pick options, and lock type.
Manhole frames and covers can be round, square or rectangular. They’re typically available as an assembly or set depending on whether assembled together before shipment.
Optional “Dump No Waste! Drains To Waterways” and other custom cast-in lettering is an effective way to support local environmental initiatives. Drainage castings or grates are typically sold with a frame, curb inlet frame, monument box, or bridge drain. Some markets call these slotted covers. Specifying the appropriate drainage solution is an important part of a storm water management plan. The wide array of products includes ditch grates, pipe grates, curb and gutter inlets and catch basins.Grating Thai has the trench drainage solution to fit your application from pedestrian areas to airport loading ramps expandable, and available in numerous widths. Designer trench grates may be standalone architectural enhancements, or can accompany matching tree grate designs.

Bridge Drain Scupper | Storm Drain Inlets offers an excellent drainage solution for bridge applications. The scupper systems collect water from bridge deck surfaces to convey this water to appropriate positions beneath the bridge. The key advantage on our scuppers is its lightweight construction.

A catch basin (storm drain inlet, curb inlet) is an inlet to the storm drain system that typically includes a grate or curb inlet where stormwater enters the catch basin and a sump to capture sediment, debris and associated pollutants. They are also used in combined sewer watersheds to capture floatables and settle some solids. Catch basins act as pretreatment for other treatment practices by capturing large sedime nts. The performance of catch basins at removing sediment and other pollutants depends on the design of the catch basin (e.g., the size of the sump), and routine maintenance to retain the storage available in the sump to capture sediment.
Catch basins are used in drainage systems throughout the United States. However, many catch basins are not designed for sediment and pollutant capture. Ideal application of catch basins is as pretreatment to another stormwater management practice. Retrofitting existing catch basins may help to improve their performance substantially. A simple retrofit option of catch basins is to ensure that all catch basins have a hooded outlet to prevent floatable materials, such as trash and debris, from entering th e storm drain system.
Most curb opening inlets depend heavily upon an adjacent depression in the gutter for effective flow interception. Greater interception rates result in shorter inlet lengths. However, a large gutter depression can be unsafe for traffic flow and bicycle operation near the gutter line. Therefore, a compromise is in order when selecting an appropriate value for the gutter depression. The depth of the gutter depression
Some municipalities in the state prefer to recess curb inlets with significant depression to minimize interference with traffic flow. The inlet is recessed from the line of the curb and gutter such that the depression does not extend beyond the gutter line. This may improve driveability; however, the curb transition may pose a hazard to traffic. Curb opening inlets are useful in sag and on-grade situations because of their self-cleansing abilities and hydraulic efficiency. Additionally, they are often preferred over grate inlets because the inlet is placed outside the travel way and poses less of a risk to motorists and bicycle traffic.
A drawback of curb opening inlets is that the flowline of the opening is fixed and not readily adaptable to changing pavement levels as occur in surface treatment overlays. Successive overlays can gradually reduce or even eliminate the original opening available for water removal, unless the pavement edge is tapered to the original gutter line.

For the most part, grate inlets are used in sag configurations in gutters, adjacent to concrete traffic barriers or rails (where curb inlets would not be practicable), V-shaped gutters with no curb or barrier, and ditches. Grate inlets may also be used at on-grade situations combined with curb inlets. Grate inlets adapt to urban roadway features such as driveways, street intersections, and medians. When grate inlets are specified, the grate configuration and orientation should be compatible with bicycle and wheelchair safety.
Access to the storm drain system through a grate inlet is excellent in that, usually, the grate is removable. On the other hand, maintenance of grate inlets can be a continuing problem during the life of the facility; the propensity to collect debris makes grate inlets a constant object of maintenance attention. As such debris accumulates it obstructs the flow of surface water into the inlet. Grate inlets also present potential interference with bicycles and wheelchairs.

Linear Drains 
Linear drains were designed for the interception of wide spread, low flow situations. Applications include intercepting sheet flow from the roadway when collection at a concentration point is not practical, or providing a generalized inlet for stagnate flow on pavements without slope. Linear drains have the advantage that no depression is necessary for hydraulic efficiency. Linear drains may be useful in problematic areas where curb and grate inlets are ineffective, such as along a median barrier, and at super elevation transitions. Linear drains can also be installed transversely across the roadway. However, linear drains have several drawbacks: Linear drains have a high propensity to collect debris in sag configurations. Regular maintenance is required to clear debris from over the drain inlet. Installation can be difficult. Because the inlet is installed flush with the surface of the pavement, placement is critical.

Slotted Drains 
Slotted drains consist of a corrugated pipe with an extended slot, or throat, at the top (see Figure 10-5). The throat of a slotted drain inlet is ordinarily reinforced for structural integrity. Slotted Drain Inlet. Slotted drains should be installed with sufficient slope to provide a cleaning velocity for the corrugations. If not, regular cleaning and maintenance must be scheduled on the slotted drain. Clean out access boxes are usually needed at the far end of each slotted drain run to facilitate regular maintenance and cleaning.

Trench Drains 
Trench drains may be precast or cast-in-place. Figure 10-6 illustrates the body and grate of an installed precast trench drain. Precast trench drain. Trench drains have the advantage of a shallower embedment depth and an extremely smooth invert that doesn’t retain sediments, but the disadvantage of having a limited volume because of their size. Trench drains on Department roadways are required to have non-removable grates because removable grates may come loose or move which will create a traffic hazard. The grates specified by the Department have a minimum of 60% open space which allows for cleaning with a vacuum truck or water truck without removing the grates.

Combination Inlets 
Combination inlets such as curb and grate can be useful in many configurations, especially sag locations. Because of the inherent debris problem in sags, the combination inlet offers an overflow drain if part of the inlet becomes completely or severely clogged by debris. Maintenance of combination inlets is usually facilitated by the fact that the grate is removable, providing easy access to the inlet and associated storm drain system. Combination inlets used on-grade generally are not cost-effective because of the relatively small additional hydraulic capacity afforded. Authentic data on such combinations are insufficient to establish accurate factors for determining the true capacity of a combination inlet. For a combination curb and grate, assume that the capacity of the combination inlet comprises the sum of the capacity of the grate and the upstream curb opening length. Ignore the capacity of the curb opening that is adjacent to the grate opening.

Inlets in Sag Configurations 
An inlet in a sag configuration is considered the “end of the line” because the water and its debris load have no other place to go. Because of this, failure of an inlet in a sag configuration often represents a threat to the successful operation of a storm drain system. Therefore, the hydraulic designer must consider some additional items such as complex ponded width and complex approach slopes. In a sag configuration, the controlling ponded width can be from one of two origins. The inlet itself may cause a head that translates to a ponded width, and the flow in the curb and gutter from each direction subtends its own ponded width. If the sag is in a vertical curve, the slope at the sag is zero, which would mean that there is no gutter capacity. In reality there is a three-dimensional flow pattern resulting from the drawdown effect of the inlet. As an approximation, one reasonable approach is to assume a longitudinal slope of one half of the tangent grade. Because the water or its debris load can go no other place, an appropriate safety factor should be applied to the inlet size. For grate inlets in sags, the usual safety factor is approximately two; for curb inlets, the factor can be somewhat less. In application, the factor of safety for a grate inlet is applied as a safety reduction factor, or clogging factor. For example, a safety factor of 2 would result in a clogging factor of 50%, which assumes that half the grate is clogged by debris. Where significant ponding can occur such as in an underpass and in a sag-vertical curve, good engineering practice is to place flanking inlets on each side of the sag location inlet to relieve some or most of the flow burden on the inlet in sag. Flanking inlets should be analyzed as inlets on-grade at some specified distance (usually 50 or 100 feet) away from the low point on the sag vertical curve.

Median/Ditch Drains 
Drains or inlets appearing in ditches and medians are usually grate inlets and are also termed “drop inlets.” The operation of the inlet is enhanced by a concrete riprap collar that forms a type of bowl around the inlet. Often, such an inlet is in a sag (sump) configuration created by a ditch block. Department research ( 0-5823-1) indicates that a six inch ditch block may not be adequate to ensure complete capture of flow; a taller ditch block may be necessary. However, the designer must either determine the required depth for complete capture, or account for flow over the ditch block to the next inlet. Care must be taken to ensure that the ditch block slopes meet clear zone standards.

Drainage Chutes 
Drainage chutes, also referred to as over-side drains or curb slots, are commonly used at the ends of bridges to either prevent flow from running onto a bridge deck, or to prevent flow from running off a bridge deck onto the pavement. There may be other locations where a drainage chute or curb cut may be useful in removing flow from the pavement where no storm drainage system is present and where suitable outfall is present behind the curb and gutter section. In most cases, an opening in the curb connects to a scour-resistant channel or chute which prevents erosion of the embankment or slope. In some instances, the channel or chute may be replaced with a pipe placed in the roadway embankment as illustrated in Figure 10-8. This treatment facilitates mowing and other maintenance but also introduces its own maintenance needs to keep it from clogging.

Inlet Locations 
The inlet location may be dictated either by roadway elements, hydraulic requirements, or both. Inlets should be placed upstream of roadway elements such as sags, street intersections, gore islands (see Figure 10-9), super elevation transitions, driveways, cross-walks, and curb ramps (see Bypass Flow Design Approach). Flow across intersections, ramps, and to a lesser extent, driveways, may cause a traffic hazard, while flow across cross-walks and curb ramps may cause a pedestrian hazard. Inlets at these locations should be designed to capture 100% of the flow. Inlets should also be located hydraulically to prevent excessive gutter flow and excessive ponding.

Drain inlets collect water from roads and parking lots and convey it to an underground storm drain system. Drain inlets incorporated into a curb and gutter systems are called curb inlets. Drain inlets have minimal water quality benefit alone; however, in a developed watershed they are often a necessary component of a drainage system that as a whole has a water quality benefit. There are design elements that can be incorporated into a drain inlet to achieve some water quality benefit.
APPLICABILITY Drain inlets are suitable along paved roads, parking lots, paved swales, or rock-lined ditches where permanent storm drain system are currently installed or planned to be.
Drain inlets Advantages Prevents discharge of degraded runoff water from roadside ditches and Reduces discharge velocity from culverts/curbs by dissipating energy.