Crew ran a French drain from a soggy side yard: 4-inch perforated pipe, holes up, laid in a level trench with pea gravel dumped straight on the clay, then ran it 40 feet into a 'dry well' they dug 2 feet deep in the same clay.

Three fundamental errors, any one of which kills the system:

1. Holes up. Perforated pipe goes holes down (4 & 8 o’clock). Holes up lets water in only after the trench floods to the pipe crown. IRC R405.1 requires pipe to be "laid on a bed of gravel" with holes down to intercept water at the trench bottom.
2. No separation fabric. Pea gravel dumped directly on clay silts up in one season. You need non-woven geotextile (4–6 oz) lining the entire trench—bottom, sides, and wrapped over the top—before stone goes in. This keeps clay fines out of the void space.
3. “Dry well” in clay with a high water table. A 2-ft hole in impermeable clay 18 in. below seasonal water table is a sump, not a dry well. It fills instantly and stays full. Water has nowhere to go.

Fix:

• Re-trench with positive slope (min. 0.5% / 1/8" per ft) to daylight or a pumped basin.
• Line trench with fabric. Lay 4" SDR-35 or Schedule 40 perf pipe holes down on 2" of washed ¾" stone (not pea gravel—round stone won't lock).
• Backfill with same washed stone to 6" above pipe. Fold fabric over. Top with native soil/sod.
• If no daylight exists, install a sealed sump basin with a 1/3 HP effluent pump and discharge to storm sewer or curb (check local ordinance). A passive pit in clay does not work.

Bottom line: You built a clay-lined bathtub with a clogged drain. Dig it up and do it right.

The yard remains wet because the French drain and dry well are fundamentally flawed for your conditions—this design won’t work in clay with a high water table.

Key failures:

1. Holes up? Perforated pipe must have holes down (typically at 4 or 8 o’clock) to let water enter from the surrounding soil. Holes up means water can’t enter the pipe—it just sits in the gravel, defeating the purpose.

1. Level trench? French drains need minimum 1% slope (1/8" per foot) toward the discharge point. A level trench means no gravity flow—water pools in the pipe.

1. Dry well in clay? A 2-foot-deep dry well in clay is useless. Clay has permeability of ~0.0001 ft/day—water won’t percolate. At 18" water table, the dry well is likely below the seasonal water table, so it’s just filling with groundwater, not absorbing it. It’s now a sump, not a dry well.

1. No filter fabric? Pea gravel dumped straight on clay allows fines to migrate into the gravel, clogging it over time. Geotextile fabric between soil and gravel is essential.

1. Insufficient depth? With water table at 18", the drain should be below that—ideally 24–30" deep—to intercept groundwater before it reaches the surface. Yours is likely too shallow.

Fix:

• Re-dig trench with 1% slope to a proper discharge (daylight, storm drain, or sump pump).
• Use 4" perforated pipe, holes down.
• Wrap pipe in geotextile fabric, then surround with ¾" clean crushed stone (not pea gravel—too fine).
• Extend trench below water table (min 24" deep).
• Abandon the clay dry well—it won’t work. Instead, daylight the drain to a lower area or install a sump pump with discharge to storm sewer (check local codes—often requires permit).
• Consider a curtain drain (interceptor) uphill of the soggy area to divert groundwater before it arrives.

Code reference: IPC Section 1101.3 (subsoil drains) requires proper slope, filter media, and discharge. IRC R405.1 covers foundation drains—similar principles apply.

Unlicensed work? If this involves altering drainage patterns or connecting to municipal systems, a licensed contractor or engineer may be required. Do not guess—consult a civil engineer or licensed drainage contractor for a site-specific solution. Clay and high water tables demand professional design.