Diagnose standing water
Timebox: one hour, best spent during or just after rain. Output: a verdict — swale, pipe, regrade, gutter repair, or “this puddle is doing its job.” The check is three numbers plus one walk. Buying a fix before this walk is how French drains end up in yards that needed gutters.
Checked 2026-09-10 · procedure re-verified against sources below
The walk
Stand at the puddle. Find where its water comes from — the roof, the neighbor, the hill, the soil itself — and where it goes, if anywhere. Walk both paths. The puddle's watershed is rarely where the puddle is; the catchment is usually upslope or up-pipe.
The three numbers
- Grade — along the path the water should take. Under 1% and the ground itself is the dam.
- Perk rate — at the puddle's bottom, presoaked. Under 0.5 in/hr and the soil is the dam.
- Catchment — the area feeding the puddle. Big roof, small yard: the roof is the dam, wearing gutters.
The verdict table
| You measured | Verdict | Fix |
|---|---|---|
| Grade < 1%, soil fine | Flat ground | Swale with a real outlet, or regrade toward one |
| Perk < 0.5 in/hr | Tight soil | Conveyance: French drain to daylight or basin with outlet — not infiltration |
| Huge roof catchment | The roof | Gutters and downspouts first — the downspout math |
| All three fine | Working detention | The puddle drains within 72 h and holds a storm by design. Leave it — see the 72-hour rule |
| Water seeps up, not down | High water table | No passive fix at the surface. Engineer or accept — see dry well gates |
Where people stop
- Diagnosing in dry weather. A dry yard hides its sources. The storm is the survey; schedule the walk for the next real rain.
- Fixing the puddle, not its supply. Regrading the low spot while the downspout keeps pouring into it is bailing with the tap open.
- Buying first, measuring never. Every product on the market will happily be sold for the wrong disease.
Where to go next
- Measure grade — number one, 30 minutes.
- Perk test — number two, one day.
- Calculate catchment — number three, 30 minutes.
Sources
- Minnesota Stormwater Manual — Infiltration — supports how infiltration practices behave when the soil will not take water.
- USGS Water Science School — Infiltration and the water cycle — supports what infiltration does and does not do underground.
- US EPA — Stormwater discharges from municipal sources — supports municipal requirements triggered by standing water.