How much a drain or sewer pipe must fall over its length, and if the flow will self-clean.
How this works
Drop = length / gradient, so 10 m at 1:40 falls 250 mm. Typical gradients: 100 mm pipe 1:40 to 1:80, 150 mm pipe 1:60 to 1:150. Half-full speed (Manning, n = 0.009 for PVC) should be at least 0.75 m/s so solids are carried away.
Questions people ask
How do I use the Drain Pipe Slope tool?
Fill in the fields, starting with “Pipe length”, “Pipe size” and “Gradient”, and change any other options that match your home. The answer, a drawing and practical tips update as you type, and the Copy link button saves your numbers in a link you can share.
Is the Drain Pipe Slope tool free?
Yes. The Drain Pipe Slope tool is free, with no sign-up, and works on phones, tablets and computers. The results are estimates to help you plan, so check with a qualified professional before structural, electrical, gas or plumbing work.