Flo-Well Detention Systems: Underground Water Management

 When surface water or roof runoff is captured by a drainage system, it has to go somewhere. But what happens if a property is completely flat, or the surrounding yards sit at a higher elevation? If the water cannot naturally flow away using gravity, it must be managed on-site. Flo-Well detention systems act as a massive subterranean holding tank, engineered to capture, hold, and safely dissipate several gallons of water deep underground. 

 A Flo-Well (or dry well) is a high-capacity, heavy-duty underground chamber. Unlike a solid tank that simply stores water, the sides and bottom of a Flo-Well are entirely open or perforated.

Think of it as a massive, underground sponge. Instead of forcing heavy stormwater to flood the surface of a yard, the system provides a hollow, structural void deep in the earth where bulk water can safely park while it slowly percolates back into the surrounding soil.

 Underground detention operates on a simple cycle of collection, storage, and dissipation.

• Collection: Water from an underground pipe network (fed by downspouts, catch basins, or channel drains) is routed directly into the top or side of the buried Flo-Well unit.
• Detention: During a heavy storm, the ground often cannot absorb water as fast as it falls. The Flo-Well acts as a buffer, filling up and safely holding massive volumes of water inside its hollow chamber.
• Dissipation (Leaching): Long after the storm passes, the trapped water slowly and naturally leaches out through the perforated sides and open bottom, sinking into the deep subsoil completely out of sight.

 An underground detention system is required if a property presents any of the following challenges:

• No Natural Exit Point: The yard is totally flat or sits at the bottom of a hill, meaning gravity cannot be used to push the water to a street or woodland area.
• Municipal Regulations: Many local city codes and HOA rules strictly prohibit discharging storm water onto the street, sidewalks, or into neighboring properties.
• Heavy Surface Clay: The top layer of soil is so dense and compacted that water pools on the surface. A Flo-Well bypasses this hardpan layer, delivering the water to the looser, more absorbent soil layers deeper underground.
• Massive Roof Runoff: The home's gutters output too much water for a standard pop-up emitter to handle without turning the lawn into a swamp.

 Digging a hole and burying a plastic bucket will fail within a year. A true detention system requires massive excavation and exact engineering.

Here is the Go Away Drains premium standard for underground water management:

• Massive Excavation & Capacity: We don't just dig a standard hole; we excavate a massive 5-to-6-foot deep by 5-to-6-foot wide subterranean pit. We place professional-grade NDS Flo-Well units at the center of this void. This massive footprint is engineered for one specific purpose: to hold and manage massive amounts of bulk water. If a property requires extreme water management, we will link multiple units together in a series to multiply the holding capacity.
• The River Rock Difference: A Flo-Well needs space around it to work. General contractors will often backfill a pit with the dirt they just dug out—which instantly turns into mud and permanently clogs the system. We exclusively backfill the massive void around our units with clean, washed 1.5” River Rock. This creates a highly porous environment that drastically increases the total water-holding capacity of the entire 5x6 pit.
• Total Soil Protection: We wrap the entire Flo-Well and river rock system in a heavy-duty, non-woven geotextile filter fabric. This acts as an impenetrable shield, allowing water to leach out while physically preventing the surrounding mud from washing in and clogging the system.
• Strategic Relief Valves: If a system is engineered to take on multiple heavy runoff discharges at once (such as routing several downspouts and a driveway drain into a single pit), we install a surface-level pop-up emitter to act as an overflow valve. In the event of a 100-year mega-storm, this safety relief guarantees that if the massive underground system ever reaches absolute maximum capacity, the excess water will safely bubble to the surface rather than backing up the pipes toward the house.

 Because these systems require heavy excavation, massive amounts of river rock delivery, and dirt haul-away, pricing is directly tied to the engineered size of the pit.

For a professionally installed Go Away Drains detention system—including the heavy-duty units, excavation, premium river rock backfill, and complete fabric wrapping—clients typically invest between $1,500 and $3,500+ per detention zone.

Because guessing leads to hidden costs, we offer our comprehensive $65 Drainage Evaluation. We will come to your property, calculate the exact volume of water coming off your roof or driveway, engineer the precise size and depth of the pit required, and hand you a fixed, line-by-line blueprint. You’ll know exactly what the permanent solution will cost, with zero surprises.

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