Drain Slope Calculator

Calculate the proper slope for drain pipes per plumbing code. Enter your pipe run length and diameter to find the total drop needed, trench depth at each interval, and compare trenching costs.

Pipe Diameter

Pipe Run Length (ft)

Starting Elevation (in)

Trenching Costs (edit to match local rates)

Hand Dig ($/ft)

Machine Dig ($/ft)

Excavator Rental ($/day)

Drain Slope Profile

Total Drop Needed

12.50"

Over 50 ft run

Ending Elevation

11.50"

From 24" start

Slope

2.08%

Ratio 1:48

Pipe Diameter	Total Drop & Slope	Code Requirement
1-1/2" Pipe	12.50" drop (2.08%)	1/4"/ft
2" Pipe	12.50" drop (2.08%)	1/4"/ft
3" PipeBest value	12.50" drop (2.08%)	1/4"/ft
4" Pipe	6.25" drop (1.04%)	1/8"/ft

Trench Depth Profile

Distance (ft)	Elevation (in)	Drop from Start (in)
0	24.00	0.00
10	21.50	2.50
20	19.00	5.00
30	16.50	7.50
40	14.00	10.00
50	11.50	12.50

Cheapest Trenching: Hand Dig — $750.00For a 50 ft pipe run with 3" Pipe, you need a total drop of 12.50 inches (1/4" per foot per code). The most cost-effective trenching method is hand dig at $750.00.

Slope requirements are based on the International Plumbing Code (IPC). Local codes may differ. Always verify requirements with your local building department and hire a licensed plumber for permitted work.