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Drain-water Heat Recovery Greywater Recycling Basics

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What Is Greywater?
Greywater is any household wastewater with the exception of wastewater
from toilets, which is known as blackwater. Typically, 50-80% of household
wastewater is greywater from kitchen sinks, dishwashers, bathroom sinks,
tubs and showers. Of course, if you use a composting toilet, 100% of your
household wastewater is greywater.
Water Fact:
As water filters through the
biological surface layer of Freshly generated greywater is not as nasty as blackwater, but if it's not
soil, it is purified by handled properly it can soon become so. Greywater decomposes at a much
microorganisms and plant faster rate than blackwater and if stored for as little as 24 hours, the
roots.
bacteria in it use up all the oxygen and the greywater becomes anaerobic
and turns septic. After this point it is more like blackwater - stinky and a
Let's Go Green Inc. health hazard. In fact, many jurisdictions have strict regulations about
911 Ranchview Cres NW
disposal of greywater, some even require it to be treated as blackwater.
Calgary, Alberta
Canada T3G 1A4
1-888-248-9754 Not all greywater is equally "grey". Kitchen sink water laden with food solids
and laundry water that has been used to wash diapers are more heavily
contaminated than greywater from showers and bathroom sinks. Although
greywater from these sources contains less pathogens than blackwater,
many regulatory bodies consider it as blackwater.

The safest way to handle greywater is to introduce it directly to the

biologically active topsoil layer, where soil bacteria can quickly break it
down, rendering the nutrients available to plants. This biological water
purification is much more effective than any engineered treatment, thus
protecting the quality of groundwater and surface waters.

Benefits of Greywater Recycling For Irrigation

Reduce fresh water use - When the weather is warm, about half of
the water consumed by the average household in North America is for
outdoor use. Capturing the indoor greywater for use outdoors can cut
water usage in half.

Reduce strain on septic system or treatment plant - Greywater

makes up the majority of the household wastewater stream, so
diverting it from the septic system extends the life and capacity of the
system. For municipal systems, decreased input means more effective
treatment coupled with cost savings.

Develop otherwise unsuitable real estate - A greywater recycling

system, along with the use of composting toilets, can enable the
development of property that is unsuitable for a septic system.

Groundwater Recharge - Greywater recycling for irrigation

replenishes groundwater, helping the natural hydrologic cycle to keep
functioning.

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Plant growth - Greywater can support plant growth in areas that

might otherwise not have enough water.

Maintain soil fertility - The nutrients in the greywater are broken

down by bacteria in the soil and made available to plants. This helps
to maintain soil fertility.

Enhance water quality - The quality of groundwater and surface

waters are much better preserved by the natural purification processes
the greywater undergoes in the top layers of the soil than by any
engineered water treatment.

Satisfaction - The greywater user gets the satisfaction of direct

participation in the responsible management of global nutrient and
water cycles.

Greywater Irrigation May Not Be A Good Choice

If:
Soil is not suitable - If your soil is either too permeable or not
permeable enough, you may not be able to recycle your greywater, or
you may need a system with some modifications.

Area too small - You need enough soil to process the greywater and
enough plants to use it.

Climate unsuitable - If it's too wet to benefit from irrigating with

greywater, there may be a better way to dispose of it. If it's too cold,
you will only be able to recycle in the warmer months. In cold
climates, the heat in greywater may be more valuable than the water
itself. See Drain-water Heat Recovery.

Permit hassles - Many jurisdictions in North America have no clear

guidelines regarding greywater processing. With water shortages
looming in the near future for many regions, this may change sooner
than later. Health concerns are often cited as the reason for not
allowing greywater recycling, although there has never been a
documented case of somebody becoming sick as a result of exposure
to greywater.

Low cost/benefit ratio - Where legal requirements dictate a complex

system and there is only a small flow of water, greywater recycling is
not economically feasible.

Inconvenience - If the greywater system you are considering is

more expensive and requires more maintenance than a properly
functioning septic or sewer system.

To recycle greywater safely, users must understand the nature of the grey
water itself as well as the natural cycles and processes involved in the
purification of it. Each set of circumstances requires its own unique recycling
system for optimum results.

For most residential purposes, low-tech, home made grey water systems
tend to outperform and outlast expensive pre-made systems.

Greywater Recycling Health Concerns

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Health risks are often cited by regulators as reasons for requiring high-tech
expensive systems although there are no recorded instances of greywater–
transmitted illness in the US. However, greywater may contain infectious
organisms. Bear this in mind when designing and using a system. A poorly
designed system could become a pathway for infecting people.

Two main principles for safety:

Greywater must pass slowly through healthy topsoil for natural

purification to occur

Design your greywater system so no greywater-to-human contact

occurs before purification (ie: passing through the soil or mulch basin)

Precautions

Prevent contact or consumption - Avoid accidental connections

between freshwater and greywater plumbing

- Label greywater plumbing, including garden hoses

- Use gloves when cleaning greywater filters

- Wash your hands after contact with greywater

Microorganisms on plants - Don’t apply untreated greywater onto

lawns, or fruits and vegetables that are eaten raw (eg. strawberries,
lettuce, carrots)

Breathing of microorganisms - Don’t recycle untreated greywater

with sprinklers. Droplets can evaporate leaving harmful
microorganisms in the air where they can be breathed in

Use only greywater that is fairly clean to start with - Greywater

containing water used to launder diapers or generated by anyone with
an infectious disease should be diverted to a sewer or septic system

Don’t store greywater - Use it within 24 hours before bacteria

multiply. After 24 hours it is well on its way to becoming blackwater

Don’t overload your system - If you’re having company and your

system is designed for 2 people, divert the greywater to the sewer or
septic system for the evening

Chemical contamination - Don’t buy household cleaning products

you wouldn’t want in your greywater system. Divert greywater
containing harmful chemicals to the sewer or septic system

Prevent contamination of surface water - Discharge greywater

underground or into a mulch filled basin

- Don’t apply greywater to saturated soils

- Apply greywater intermittently so it has a chance to soak in and the

soil can aerate between waterings

- Confine greywater to subsurface or mulch basins at least 15m from

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a surface waterway

Elements Of A Greywater Irrigation System

Greywater source(s) - Washing machine, shower, bathtub and/or

sinks

Collection plumbing - Pipes that transport greywater from inside the

house to just outside the house

Surge Tank, filter and pump - Optional elements that add

complexity and cost but make the distribution plumbing's job easier

Distribution plumbing - Pipes that transport greywater from just

outside the house to locations throughout the receiving landscape

Receiving landscape - Soil, roots, plants, and mulch basins that

contain, cover, purify, and use the greywater

People - Those who design, make and maintain the system, generate
the greywater, tend the garden and eat the food it produces. People
are a critical but often overlooked component of the system

Types of Greywater Irrigation Systems

Drain To Mulch Basin

Features

no filter

no pump

no surge tank

uses very little pipe

little or no
maintenance

low economic cost

low ecological cost

anyone can build it

failure rate is low

lasts forever

Branched Drain

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Features

same as drain to
mulch basin

higher economic &

ecological costs are
offset by capacity
to handle higher
volumes of
greywater

uses multiple mulch

basins

contains & covers

greywater in the
landscape

automatically
disperses greywater
to several locations

Constructed Wetland

Features

ideal for wet climates

good where soil perk is low and space is restricted

good for treating larger volumes before reuse

poor choice in dry climates

reduced reuse efficiency due to uptake by wetland plants

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efficiently treats blackwater as well as greywater

Solar Greywater Greenhouse

Features

highest ecological net gain for cold

climates

allows year-round treatment of

greywater

solar greenhouse helps heat the

house

food production

conserves the heat in the

greywater

Other Suggestions For Cold Climate Greywater Irrigation

continuous downhill slope in all plumbing

no standing water so there's nothing to freeze

heat in the greywater may keep pipes in the distribution plumbing

clear into the frost season if there is sufficient insulation (mulch,
leaves etc.)

minimum 6 inches fall at discharge outlets to prevent ice buildup

clogging outlet

ground should slope sharply away from the outlet at first, then may
gradually flatten

apply the greywater in a warmer microclimate, eg. the south and west
side of a house with a windbreak to the north will be significantly less
frosty and may extend your irrigation season

Greywater As A Heat Source

in cold climates, the heat in the greywater may be its most valuable
aspect

Drain-water heat recovery extracts heat from shower drain water and
use it to preheat water entering the hot water heater. Click here for
more information on drain-water heat recovery.

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Choose The Right System For You

Greywater systems are very context-dependent. There is no universally ideal

system. Choose your system based on:

site

greywater sources

irrigation needs

soil percolation rate

climate

water availability

Before You Start: Get Clear On Your Goals

What is your overall environment? Upscale neighbourhood or a

country cabin?

What other lifestyle changes are you willing to make regarding water
conservation?

What is your standard of perfection?

Are you trying to use or dispose of your greywater?

How important is it to increase reuse efficiency?

Expected economic payback time

Landscape goals

Other goals

Common Greywater Errors

Assuming it's simple - Failure to realize that a greywater irrigation

system that achieves your goals is a site-specific and user-specific
design issue almost any other green home technology

Out of context design - Constructed wetland in the desert or

irrigation of a swamp

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Overly complex, delicate, or expensive system - A typical

residential greywater system saves $5 to $20 worth of freshwater per
month. If the system costs more than a few $1,000 the owner and
the earth are probably better off wasting the water than the pumps,
valves, fittings, piping, filters, and electricity

Exceptions

- During drought, or where water is otherwise unavailable

- Where there are acute water disposal problems

- Where a high volume of greywater co-exists with a high need for

irrigation

Mansion with a greywater system - The value of the greywater is

negligible compared to the other waste. Trying to capture the
greywater just adds more waste in the form of hundreds of feet of
extra plumbing

Pump zeal - Pumps won't work without filtration and filters clog
quickly due to the high solids content in greywater. Pumps shorten
the life of your system, and you may be substituting electricity waste
for water waste

Storage of greywater - Bacteria multiply to blackwater levels very

quickly

In Conclusion

Conserve Water First - Before implementing any greywater system, be

sure you have taken all possible measures to conserve water, for example:

low flow shower heads

low flush/composting toilets and "If it's yellow let it mellow" policy

aerators on faucets

efficient front loading washing machine

natural landscaping

rainwater harvesting

Follow Ecological Design Principals - The greatest efficiency (and quality)

is achieved when the power of the tool is well matched to the task at hand.
Choose the simplest design that meets your needs and build it as well as
you can. Consider the ecological cost of the system components.

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The information on this page is used with the kind permission of Art Ludwig.
Art is an ecological systems designer who has done extensive work with
greywater systems. For more information, please visit his website
www.oasisdesign.net where you'll find more than 300 pages of information
about greywater as well as the leading books on greywater.

© 2005-2009 Let's Go Green Inc. ~ All Rights Reserved ~ Learn About Greywater Recycling

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