Flashboard Riser Inlet Structures Our Flashboard Riser Inlet Structures are perfect for larger ponds and impoundment drains where significant water flow must be accommodated. These are also known as dropboard risers, weirs or monks.
Key Features
Heavy-duty welded steel structures: Resists twisting and bending.
Precision laser cut and formed parts: Accurate fit up with accessories
Designed For HDPE Pipe: Designed to work with double-wall corrugated high density polyethylene drain tiles from 8” to 30” in diameter.
Corrosion Resistant: Powder coated for long-lasting corrosion resistance.
Standard Lumber Flashboards: Designed to accept standard “2 by” dimensional lumber as flashboards.
Debris Guards: We offer optional trash guards to keep floating debris and beavers out of the inlet box.
Support Frames: We offer optional support frames to prevent floating, slipping and leaning.
Fabricated in the USA
Important Considerations
Safety Large pipes and taller inlet structures can present safety risks. High head pressure combined with large water flow can create significant suction forces that could pull people or animals into the drain. Use appropriate fencing and safety grates to prevent accidental access.
Floating, Leaning and Sliding are important design factors that are often overlooked when installing single-sided flashboard riser structures.
Floating Single-sided box-type flashboard inlet structures want to “float” when the water is blocked and the inlet box is dry.
Leaning and Sliding The weight of soil behind tall structures can push on the back causing the structure to lean forward and slide away from the bank. These factors are magnified in loose and soggy soil conditions where the soil slumps excessively.
Water Pressure can generate surprisingly large forces on the lower flashboards and the structure in general. These forces multiply with the width and height of the structure. Lower flashboards in a tall structure will experience higher pressure and can be difficult to remove on wide or tall structures.
See more explanation of these Forces here
See comments on Corrosion here
Wooden Flashboards made from ordinary lumber do not provide a perfect seal. They will leak a little bit when first installed. They will naturally swell and seal up with mud, algae and debris in a short time. The small amount of leakage is not a problem when ample water flow is available. If necessary, an immediate watertight seal can be achieved by using the widest possible flashboards and placing sealing material between the flashboards.
Installation is Straightforward Our standard units are designed to be installed with simple tools. A drill or impact driver with a 5/16 socket is required. A 9/16- inch socket is required to attach options. No concrete or welding are required.
Prepare the area in front of the drain tile to receive the bottom section. The soil should be packed firmly to minimize settling.
Bolt the optional support frame and/or debris screen to the corresponding anchor points on the box using the hardware supplied
Slip the skirt on the bottom section of the box into the inside of the plastic drain tile. Check the fitment of the tile to the base and adjust as required. Do not force or deflect the drain tile to force the connection.
Ensure the box is upright and level in both directions. If the optional support frame is used, adjust the length of the struts if required.
If desired, drive rebar earth anchors through the base to secure the unit.
Install the pipe following the instructions below.
Place the flashboards into the box
Backfill as desired ensuring that large rocks or clumps of earth do not damage the pipe, box or support frame.
Mounting the Pipe is Simple. The nipple on the back of the riser is formed to provide a slip-fit for the designated pipe diameter.
Slide the pipe over the nipple and position the supplied cleat on the side as shown. Using a powered screwdriver or drill with a 5/16 socket, drive the supplied self-drilling screws through the pipe and into the nipple as shown in the video. We recommend starting with the center two screws then the outer screws. Repeat on the opposite side using the second cleat.
These cleats provide a robust connection that will not easily rip out or tear the pipe. The cleats can optionally be mounted by bolts extended from the inside of the nipple if you prefer not to have the points of the self-drilling screws extending into the pipe. Simple drill holes and place bolts from the inside and fasten the cleats with nuts.
The bell-end of the pipe will be very loose on the nipple. Simply cut the bell off just before the first rib for a nice fit.
Flashboard Brackets and Puller
We provide optional Flashboard Brackets and a T-Handle Puller to make flashboard extraction easier, and safer.
The brackets bolt to any 2-X lumber and are powder coated for durability.
The T-handle has extensions that facilitate different lengths and the angle of the handle relative to the business end can be controlled.
Works with the debris guard in place.
Sealing Large Diameter HDPE Pipe Connections
Our in-line units are provided with sealed couplings. Even with properly sized couplings, achieving a truly watertight seal is difficult with corrugated pipe couplings. The seal is not critical on the outlet side because the coupling is not under pressure. Leaking can be a problem on the inlet side of an in-line structure if the seal is not watertight. The problem is magnified on taller structures with more head pressure. An optional step involves applying an adhesive between the pipe and the inlet sleeve on our in-line unit. Few adhesives adhere well to polyethylene. We recommend a liberal coating of Dupont (formally Dow) U-418HV, U-428HV or U-438HV urethane adhesive on the inlet sleeve prior to final installation of the pipe. These single-part adhesives cure into a tough but pliable urethane rubber. The glue does not truly bond to the HDPE pipe but it makes a great form-fitted gasket. Use caution because these adhesives are tenacious and are hazardous. They make a mess of everything they inadvertently touch. They do not wash off. Wear disposable gloves and protective clothing. Follow the manufacturer’s instructions and wear the appropriate PPE.
Ditch Dam Flashboard Structure
Our "ditch dam" flashboard risers are flow-through channels designed to be installed in a ditch. They are perfect for providing a couple feet of adjustment for pond levels or diverting water between ditches. They are also useful as a "check dam" to slow water flow in a ditch and catch sediments. Check dams are commonly used in desert areas to increase the rate of water absorption into the soil by slowing the water flow and allowing it to soak in. Our ditch dams do not attach to a pipe. The units are made from heavy-gage powder coated steel and come in a range of widths and heights. Installation is simple. Just place them in the ditch, tamp them down and backfill along the sides.