Rainwater Harvesting for Drylands and Beyond by Brad Lancaster

How to Get Slope Right on Gravity-Fed Greywater Distribution Plumbing

Gravity-fed greywater distribution plumbing should maintain a minimum 2% slope (1/4-inch drop per linear foot or 2-cm drop per linear meter). My favorite tool for measuring pipe slope is an Empire 12-inch magnetic tool box level, with Vari-Pitch vials that read slope in 1/8th-inch increments.

The vials can be turned to change the direction from which their markings can be read. All the following images use this tool.

Note that the following is meant as a supplement to the greywater-harvesting chapter in my book Rainwater Harvesting for Drylands and Beyond, Volume 2 and Art Ludwig’s Create an Oasis with Greywater. Read those books, as they have key additional info not included here!

Empire 12-inch magnetic tool box level with its magnet up and grooved side down, so slope measurements can be read from the side of the level. Here it measures a ¼-inch per linear foot drop/slope on 2-inch diameter ABS plastic greywater pipe.
See next slides for close ups and different orientations

 

The level reading level. Note how bubble in vial on left is between the lines, while right edge of bubble on right touches and reads 0 — both signify level.

The level reading a 1/8th-inch drop per linear foot drop/slope. Note how bubble in vial on left has crossed over the right line, while right edge of bubble on right touches and reads 1/8th-inch.

The level reading 1/4-inch drop per linear foot drop/slope. Note how bubble in vial on left has completely crossed over the right line, while right edge of bubble on right touches and reads 1/4-inch.

 

Empire 12-inch magnetic tool box level with its grooved side up and its magnetic side down. Vari-Pitch vial has been turned so slope measurements can be read from above via the slots in the grooved side of the level.
See next slides for close ups

The level reads level. Note how edge of bubble in vial touches and reads “0”

 

The level reads 1/8th-inch drop per linear foot drop/slope. Note how bubble in vial touches and reads 1/8th-inch.

 

The level reads ¼-inch drop per linear foot drop/slope. Note how bubble in vial touches and reads 1/4-inch

Over excavate the trench for your pipe, then place pipe on mounds of dirt within the trench spaced every three feet or so.
This makes it a lot easier to raise or lower the pipe as you check its levels. Much easier than having to remove the pipe and dig the trench deeper.

 

Pipe removed from trench, so you can see the pipe’s indentations on the temporary mounds. Placing the pipe on those mounds in the trench make it easier to get the pipe’s slope correct before filling in the trench.

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Umbrella Newsletter

The Umbrella: Summer 2020

THE UMBRELLA: A catch-all of resources, events, media, and more from Brad Lancaster In this time of Covid-19 and spending more time at home to be safe, I’ve been grateful for the solace, inspiration, and bountiful sustenance my water-harvesting gardens, landscape, and neighborhood forest has provided me, my family, friends, and neighbors. Record summer heat […]

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