Quick verdict
A modular plastic dry well from NDS that assembles from three side panels and a cover into a 50 gallon underground chamber, taking a 4 inch drain pipe from a downspout, a French drain or a sump pump and letting the water soak slowly into the surrounding soil. It replaces the traditional hole full of gravel with a hollow chamber that holds far more water for its size, needs only a little gravel at the base, and stacks or links for larger storms. It bears a lawn tractor once buried.
Strengths
- Fifty gallons of storage from a chamber the size of a trash can
- Takes 4 inch S&D and Schedule 40 pipe at twelve knockouts
- Needs little gravel compared with a stone-filled soakaway
- Stacks to 8 feet deep and links side by side
- Supports pedestrian and lawn tractor loads buried
Weaknesses
- Only as good as the soil it drains into; clay stays wet
- Needs a fabric wrap to keep silt out
- Digging the hole is the real work
The overall YardToolLab Score is out of 100. Section scores are out of 10.
Where the Downspout Water Goes
A downspout that ends at the foundation soaks the basement; one that ends on the lawn makes a swamp. A dry well takes that water underground and lets the soil absorb it slowly. NDS’s Flo-Well is a 50 gallon plastic chamber that assembles from three panels and a cover, takes 4 inch pipe at any of twelve knockouts and replaces the traditional hole of gravel with a hollow that holds far more water.
This review is based on the maker’s specifications and on how modular dry wells are installed and perform generally. We have not installed this unit ourselves.
The Gravel Problem
A traditional soakaway is a pit filled with stone, and stone is mostly stone; only the gaps hold water. A hollow chamber holds water in all of its volume, which is why NDS claims two and a half times the storage of a gravel pit the same size. It also means a few bags of gravel for the base and the sides rather than a truckload.
Installing It
Dig a hole a foot wider than the chamber and deep enough that the cover sits well below grade. Put a few inches of gravel in the base. Snap the three panels together, fit the cover, wrap the assembly in filter fabric so silt stays out, and run the inlet pipe through a knockout at the slope the line needs. Backfill around the sides with gravel, then soil over the top. The chamber carries a lawn tractor once buried.
Sizing
One chamber suits one downspout from a modest roof in soil that drains. A large roof, a sump pump or heavy storms want two or three linked side by side or stacked. The test is a hole filled with water: if it drains in hours, the soil will take it; if it sits for a day, clay is the problem and the well needs company or an overflow.
What It Takes
Downspouts, French drain outlets, sump pump discharge, driveway drains. Anything that arrives in 4 inch pipe.
Honest Limits
A dry well is only a storage tank between the storm and the soil. In clay, the soil is the bottleneck and no chamber fixes that alone. Dig the test hole first.
Who Should Buy It
- Homeowners with downspouts ending at the foundation.
- Anyone finishing a French drain with nowhere to send the water.
- Sump pump owners tired of a wet lawn.
Common Owner Complaints
Slow drainage in clay. Test the soil; add chambers.
Alternatives to Consider
A second Flo-Well linked for capacity. A gravel soakaway where stone is cheap and the hole is easy. A rain garden where the water can stay on the surface.
Verdict
For a downspout or a drain with nowhere to go, this chamber is the clean way to send water into the ground, and it is the standard for a reason. Dig the test hole, wrap it in fabric and link two if the roof is large.
Full specifications
NDS FWAS24 Flo-Well 50 Gallon Stormwater Dry Well System Kit with 3 Side Panels and Cover FAQs
It takes water from a downspout or drain line, holds it underground and lets it seep into the soil over hours, instead of dumping it on the lawn or at the foundation.
Dig a hole a foot wider than the chamber and a few inches deeper, lay gravel in the base, assemble the chamber, wrap it in filter fabric, connect the inlet pipe through a knockout, backfill with gravel around the sides and soil on top.
Slowly. Dig a test hole, fill it with water and see how fast it drains. If a foot of water takes more than a day, add a second chamber or an overflow.
One chamber suits a single downspout from a modest roof in soil that drains. Link two or three for a large roof or heavy storms.
