Rainwater Harvesting for Drylands and Beyond by Brad Lancaster

Plumbing for Homeowners Guide

Greywater-collection plumbing consists of all the drain pipe in a house that is connected to the greywater pipe that exits your house and connects to the greywater-distribution plumbing/irrigation line (outside your home) in your landscape.

A great free drain-pipe guide is Plumbing for Home Owners by Klickitat County (updated 12-11-2017).

While this guide does not specifically cover greywater plumbing, it does cover key plumbing relationships such as the critical distance between a drain and a P-trap (otherwise called the horizontal length of trap arms), the elevation relationship between a P-trap weir and the fitting that connects it to a vent, correct venting of drain pipes and their P-traps, and required pipe diameters based on drain-water source.

Remember that a three-way valve (enabling you to direct drain water either to the sewer/septic line, or to the landscape) should installed downstream of the drain’s P-trap and vent.

A greywater line should also always be upstream of any blackwater flow, e.g., the water from a toilet. This is because if any blackwater mixes with greywater, then all the water becomes blackwater, which is far dirtier and more difficult to manage than greywater.

Blackwater drain pipe from toilets is usually 3 inches (75 mm) in diameter, while drain pipe from greywater sources, such as bathroom sinks or showers, is usually 1.5 inches or 2 inches in diameter.

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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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