Graywater Systems


For several very simple graywater applications, see Water Conservation Methods page under shower, laundry and dishwashing headings.

Greywater systems designed for homes with conventional plumbing are well-covered in the references noted at the bottom of this page, so here I'll just describe a couple systems I've designed that aren't featured there.

Casa Juliana Kitchen Graywater System

Graywater from the kitchen sink is typically the most problematic residential graywater to use because it is relatively high in organic solids, oils, grease and soap which over time tend to seal up soil pores, preventing water from infiltrating the soil. Eventually the graywater becomes black, anaerobic and smelly. This can be mitigated by installing an interceptor (grease trap) that traps both grease and solids.

The system described here was an attempt to evenly distribute the kitchen graywater exiting the interceptor. A distribution hub made from a 5 gallon bucket, cement and 1/2" PVC pipe distributed graywater to 6 small infiltration chambers, irrigating papayas and bananas. The plants produced prolifically during our years at Casa Juliana.

Graywater first passes through an interceptor...

 

and is then evenly distributed through 6 pipes...

 

via a distribution hub.

 

Detail of infiltration chambers that eventually succeeded the wire ones pictured above.

Note mulch around chambers.

 

The oasis of papayas and bananas that is irrigated from this kitchen graywater system.

Again note the mulch filling the basin and covering the pipes and infiltration chambers so that no graywater surfaces.

 

The distribution system proved somewhat problematic, as the small 1/2" pipes occasionally clogged up. If I were to redesign this system, I'd retain the interceptor and mulch basin but would replace the distribution system with commercially available infiltration chambers of the type shown below.

Simple Graywater System in Oregon

This is a low-maintenance graywater system I designed for a family of four in Oregon's Willamette Valley. It handles all the graywater from the lavatory sink, bathtub/shower and washing machine. Since it does not receive kitchen sink graywater, it does not incorporate an interceptor. A basin was excavated in native soil and the excavated soil was used to construct a berm around the basin high enough to contain the graywater even during times of heavy rainfall. A row of connected infiltration chambers was placed in the center of the basin which was then backfilled with mulch, in this case wood chips, to a level above the chambers. The infiltration chambers are not subject to blockage by roots. They are available at larger plumbing supply outlets. This system irrigates a copse including a large willow tree, blackberry bushes and plums. The only maintenance required is to add mulch occasionally.

 

A graywater system of infiltration chambers in a basin that was subsequently backfilled with mulch.

 

Note that in both of these systems, mulch surrounds the graywater infiltration area. Compost also works well. Our experience is that these mediums help to prevent soil plugging due to their organic content and large particle size.

Recommended reading:

Guides by Art Ludwig:
Create an Oasis with Greywater
Branched Drain Greywater Systems
Building Professional's Greywater Guide

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