En EspaŅol
Share

Ask Mr. Smarty Plants

Mr. Smarty Plants - Effects of greywater on plants and soil

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.

Need help with plant identification, visit the plant identification page.
 
rate this answer
611 ratings

Friday - July 25, 2008

From: Nagpur, India
Region: Other
Topic: Watering
Title: Effects of greywater on plants and soil
Answered by: Nan Hampton

QUESTION:

What are the biochemical effects of greywater in plants and soil, because both are related. The effects can be harmful and as well as beneficial, can you give me the details of that?

ANSWER:

Greywater (or grey water) is slightly used household water—any water other than that from toilet flushing (called black water). This would include water from the dishwasher and kitchen drains, the clothes washer, showers, tubs, and lavatories. Kitchen water is sometimes put into the black water category because it contains a high percentage of oils, fats and food particles. Swimming pool drainage water is not recommended for greywater use because of its high salt concentration and stabilized chlorine or bromine which would be detrimental to most plants.

Greywater is used mainly for irrigation of plants but it can also be used for flushing toilets. Both uses contribute to the conservation of drinkable water that would otherwise be used for these purposes.

Storing greywater is not recommended unless it treated for bacterial growth; thus, greywater must be used when it is created. The water is an obvious benefit to plants, but it must be applied judiciously since oversaturation of the soil would not be beneficial to the roots of most plants. Other potential problems for plants depends on the level of the various chemicals included in the greywater. For instance, some plants will be more tolerant of greywater with substantial salinity; whereas, others may be sensitive. The chemical makeup of greywater varies from household to household depending on the personal habits of the members of the household and their choice in soaps and other cleaning solutions. Lanfax Laboratories in Australia has an excellent paper, Domestic Greywater, from their Laundry Products Research that gives data for the pH, the salinity, the sodium content, and the phosphorous content of greywater containing various clothes washing products. In general, greywater is alkaline because of the cleaning products it contains and, as such, should not be used on acid-loving plants (e.g., Rhododendrons). Unless greywater is treated, it is recommended that it not be used to water plants with edible roots and only surface watering should be used to protect edible leaves or fruits from possible bacterial exposure.

Several studies have investigated the effect of greywater on soil composition. A study by M. Travis, N. Weisbrod and A. Gross ("Accumulation of oil and grease in soils irrigated with greywater and their potential role in soil water repellency". Science of the Total Environment 394 (2008) pp. 68-74) suggests that oil and grease from greywater can accumulate in soils and affect the ability of the soil to absorb water—essentially making it water repellent. Another study by A. Gross et al. ("Environmental impact and health risks associated with greywater irrigation: a case study" Water Science & Technology Vol 52, no. 8 pp. 161-169) found evidence that: "Long term irrigation of arid loess soil with greywater may result in accumulation of salts, surfactants and boron in the soil, causing changes in soil properties and toxicity to plants."

For more technical articles, you could visit a university library and search their bibliographic databases. Also, there is a great deal of information available on the internet about greywater and its uses. Here are a few links:

Safe Use of Household Grey Water from New Mexico State University.

Greywater: what it is...how to treat it...how to use it from Greywater.com.

Grey Water Central on the Oasis Design page.

Introduction to Greywater Management from EcoSanRes.

 

More Watering Questions

Powdery mildew hits Rock Rose in Round Rock Texas
May 05, 2011 - My beautiful Rock Roses have gotten spots of white fuzzy "fur" on their leaves in the past month. This is not something they have ever had before and I'm worried its some kind of disease. Is it so...
view the full question and answer

Gregg's Mistflower stressed in Fredericksburg TX
August 07, 2013 - My Gregg's Mist Flower plants are very stressed. The blooms have turned brown and the leaves are drooping. Plants are receiving moderate sun, partial shade. Do they need daily watering this time o...
view the full question and answer

Grouping plants according to water needs
February 05, 2010 - Explain how appropriate design/grouping of plants of the same water needs would make irrigation scheduling easier?
view the full question and answer

Wind and erosion tolerant plants from Austin
August 05, 2013 - I recently cleared a fire break by removing cedar from around my home in West Austin. I'd like to plant the exposed NW facing slope with native shrubs and trees. Looking for selections that can wit...
view the full question and answer

Shriveling and dying of non-native impatiens
July 14, 2008 - Several years now many of my impatiens after a month or so seem to shrivel up and eventually die. They are planted in a row and not all are affected. I am not noticing any slug evidence which I would...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center