Reference Data
Every number on this page is either a published standard — FAA AC 150/5370-10 grade tolerances, IPC 2021 Table 704.1 minimum pipe slopes, typical DOT compaction requirements — or a verifiable Gradelog product fact. No survey estimates, no invented benchmarks. The governing project specification always controls in the field.
FAA grade tolerance — paved areas
±0.04 ft
Maximum allowable deviation
Source: FAA AC 150/5370-10
FAA grade tolerance — unpaved areas
±0.10 ft
Maximum allowable deviation
Source: FAA AC 150/5370-10
DOT subgrade compaction minimum
95% Proctor
Typical state DOT requirement; project spec controls
Source: AASHTO T 99 / T 180, state DOT specs
IPC min slope — 3" drainage pipe
1.04% (1/8"/ft)
Horizontal drainage pipe
Source: IPC 2021, Table 704.1
IPC min slope — 4" drainage pipe
1.00% (1/8"/ft)
Horizontal drainage pipe
Source: IPC 2021, Table 704.1
IPC min slope — 6" drainage pipe
0.52% (1/16"/ft)
Horizontal drainage pipe
Source: IPC 2021, Table 704.1
International Plumbing Code 2021, Table 704.1 — Horizontal Drainage Pipe Slope
| Pipe Diameter | Minimum Slope | Grade % | Min Velocity |
|---|---|---|---|
| 2½" and smaller | 1/4" per foot | 2.08% | 2.0 fps |
| 3" | 1/8" per foot | 1.04% | 2.0 fps |
| 4" | 1/8" per foot | 1.00% | 2.0 fps |
| 6" | 1/16" per foot | 0.52% | 2.0 fps |
| 8" and larger | see code | 0.22%+ | 2.0 fps |
Source: IPC 2021, Table 704.1. Local amendments can be stricter — the governing code for your jurisdiction controls. Check slope instantly with the free pipe grade calculator.
83
free construction calculators
No account required — slope, pipe grade, cut/fill, compaction, and more
7
report types from field data
Grade verification, sewer/utility as-builts, pad certification, compaction, daily reports, FAA and UFC formats
12
free spreadsheet templates
Daily reports, compaction logs, invert logs, and more — downloadable XLSX
4
instrument brands with CSV import
Topcon MAGNET Field, Trimble Access, Leica Captivate, Spectra Precision
$0
to start
Real free plan (not a trial); paid plans from $29/month, cancel anytime, data never deleted
100%
offline-capable field capture
Log shots, reports, and tickets with no signal; everything syncs when coverage returns
Every fact above is checkable on this site — follow the card links. We publish no usage statistics, testimonials, or survey data.
Gradelog checks every grade shot against design tolerance and generates inspector-ready reports from field data. Free plan available.