Plumbing Tools
Pipe volume and drain slope, done in your head-time.
Pipe Volume
How much water a run holds — flushing, purging, chlorination.
Water volume
65.28 gal
π r² × length
Drain Slope / Fall
Total fall across a run at your chosen grade.
Total fall1' 0.5"
Total fall (inches)12.5"
Common minimums: ¼″/ft on 2½″ and smaller; ⅛″/ft on 3″+ — confirm your local plumbing code.
Plumbing Quick Reference
- 1 ft³ = 7.48 gallons. Pipe volume = π × (radius ft)² × length ft × 7.48.
- Slope: total fall = run(ft) × slope(in/ft). ¼″/ft over 50 ft = 12½″ of drop.
- Water weight: ~8.34 lb/gal; a gallon ≈ 231 in³.
- Full-bore flow: keep drains at 1–2 ft/s to stay self-scouring — too flat clogs, too steep leaves solids.
