View list of forum discussions about the water crisis.

UPDATE: The sodium in many soaps is bad for clay soils. Not as salt (NaCl), but in other forms. Apparently, it binds chemically to clay particles in preference to nutrients, which allows nutrients to leach out of the soil. This can be reversed with calcium and organic matter. Stay tuned for more info on this. I have heard one account of a person damaging the soil in a small veggie patch by putting all of their washing up liquid on it. It reduced the water holding capacity of the soil. In the meantime, try to only use shower water and look for sodium free soap.

There is a water shortage in most capital cities, however this is mainly because we waste so much. We flush our toilets and wash our clothes in drinking water that has been sanitised at huge cost. We send a lot of water down the drain to mix with sewage when it can be used on the garden. People often get put off because they assume you have to spend hundreds or thousands of dollars on greywater systems or tanks. This is not the case and twenty dollars should get you a long way, if your house is raised. I divert shower water onto the garden and fruit trees and have not had any problems with soap. I have not bothered to get environmentally friendly soap. I also divert a lot of the roof runoff straight onto the ground without storage. It used to be illegal to use greywater, just as it used to be illegal to have a rainwater tank. But the drought has forced our politicians to quietly remove all these obstacles to avoid embarrassment.

Do’s and dont’s:

If you are using untreated greywater, do not put it all in the same spot. It is not allowed to pool or become smelly. Move the hose after each shower. Do not use kitchen sink water – I think the fats and oils are bad. Unless you use special laundry detergent, do not use the first batch of laundry water, but the rinse cycle water should be OK. Laundry water has the advantage that it is pumped out by the washing machine and may be a good option for low houses on flat ground.

garden hose fitted to S bend below shower, click for a larger image How you go about setting it up depends on the fittings you already have. What you should look for is a simple way to connect a garden hose to the water drainpipe and let gravity do the rest. Your shower needs to be well above ground level for this to work. My bathtub has an S-bend with a drain plug at the bottom. I unscrewed this and screwed in about $5 worth of fittings and now the garden hose clips directly on. This is by far the safest and easiest option. If the hose gets blocked the water just diverts down the drain into the sewage system. Make sure you use thread tape on the fittings (ask at the hardware store if you are not familiar with this). If you have an elbow with a plug instead, you will need to get a ‘water saver.’ This is a floppy black rubber funnel (see photos) that is inserted into the pipe. The wide part of the funnel expands and seals against the inside of the pipe to divert all the water. You connect your garden hose to the thin end of the funnel. Depending on the size of your pipes, you may need to trim the funnel. This is relatively easy and can be done with a pair of scissors. There are flat sections on the outside of the funnel which correspond to the internal diameter of standard pipes. You simply trim the excess rubber from above the flat section, until you get down to the correct size. If neither of these two options are open to you, you can always cut the PVC pipe and install a T-junction with an inbuilt diverter that allows you to easily switch between sending the water down to the sewer or into your garden hose.

Rubber funnel photo, click for a larger image Note that the floppy rubber funnels will slow down the water draining process. This means that a sink full of water will drain noticeably slower, and you may end up standing in an inch or two of water at the end of your shower. This prevents the shower and sink from self cleaning effectively, so you may want to go with an option like a T-junction that does not prevent excess water from draining the usual way. Alternatively, if you are using one of the other options, you may want to restrict the water flow at the plug so that as little as possible is wasted. I have done this with an old plastic peanut butter jar lid with an 8mm hole drilled in it. The lid is simply placed over the plug hole as is needed to restrict the water flow.

Inserted rubber funnel photo, click for a larger image Be careful with the hose – it needs to slope downhill most or all of the way or it will get blocked by air pockets. How much attention you need to pay to this depends on how much of a drop you have to work with and how long the hose needs to be. Note that it is OK for the last section of hose to rise upwards as the air can then escape from the free end. A 'V' shape, with one low point, works best. If you have more hose than is necessary for a particular location, it is probably better for the hose to go down to a lower point then rise back up, rather than trying to snake it back and forth over flat ground. A 'W' shape, with two low points (or more) will allow air to get caught in the middle 'rise' and stop the water from flowing.

Use thick (3/4 inch) garden hose or pipe rather than standard half inch garden hose, or something even thicker. The standard size garden hose will not let the water flow through fast enough.


Greywater, sometimes spelled graywater, grey water or gray water and also known as sullage, is non-industrial wastewater generated from domestic processes such as washing dishes, laundry and bathing. Greywater comprises 50-80% of residential wastewater. Greywater is distinct from blackwater in the amount and composition of its chemical and biological contaminants (from feces or toxic chemicals). Greywater gets its name from its cloudy appearance and from its status as being neither fresh (white water from groundwater or potable water), nor heavily polluted (blackwater). According to this definition greywater may exclude wastewater containing significant food residues or high concentrations of toxic chemicals from household cleaners etc.

In recent years concerns over dwindling reserves of groundwater and overloaded or costly sewage treatment plants has generated much interest in the reuse or recycling of greywater, both domestically and for use in commercial irrigation. However, concerns over potential health and environmental risks means that many jurisdictions demand such intensive treatment systems for greywater that the commercial cost is higher than for fresh water. Despite these obstacles, greywater is often reused for irrigation, illegally or not, in drought zones or areas hit by hose pipe bans, typically by manual bucketting. In the third world, reuse of greywater is often unregulated and is common. At present, the recycling of greywater is poorly understood compared with elimination.

Elimination of greywater

Domestic wastewater plumbing is usually combined at the sewer, so that grey and black waters are removed together using a shared sewerage system. Sewage water can then be treated to limit pollution and health risks, before being returned to the environment at large. The majority of greywater ends up as effluent in rivers and oceans in this way.

Recycling of greywater

Most greywaters are much easier to treat and recycle than blackwaters, due to their lower levels of contamination. However, entirely untreated greywater is still considered to be a potential health and pollution hazard.

If collected using a separate plumbing system to blackwater, domestic greywater can be recycled directly within the home and garden. Recycled greywater of this kind is never clean enough to drink, but a number of stages of filtration and microbial digestion can be used to provide water for washing or flushing toilets; relatively clean greywater may be applied directly from the sink to the garden, as it receives high level treatment from soil and plant roots. Given that greywater may contain nutrients (e.g. from food), pathogens (e.g. from your skin), and is often discharged warm, it is very important not to store it before using it for irrigation purposes, unless it is treated first.

There are numerous "soft" processes based on natural biological principles such as using reedbed filter systems, the wetpark systems or the living wall that can be used to clean up greywater.

There are also "hard", direct processes, such as distillation (evaporation) which need not necessarily be as energy intensive as they might initially appear. There seem to be no commercially available "hard" greywater recovery devices suitable for on-site use in the individual household, even though a number of such technologies exist..

Some municipal sewerage systems recycle a certain amount of grey and black waters using a high standard of treatment, thus providing reclaimed water for irrigation and other uses.

Application of recycled greywater

Greywater typically breaks down faster than blackwater and has much less nitrogen and phosphorus. However, all greywater must be assumed to have some blackwater-type components, including pathogens of various sorts. Greywater should be applied below the soil surface where possible (e.g. in mulch filled trenches) and not sprayed, as there is a danger of inhaling the water as an aerosol.

However, long term research on greywater use on soil has not yet been done and it is possible that there may be negative impacts on soil productivity. If you are concerned about this, avoid using laundry powders; these often contain high levels of salt as a bulking agent, and this has the same effect on your soil as a drought.

Domestic use
Recycled greywater from showers and bathtubs can be used for flushing toilets, which saves great amounts of water. Many attempts at this have been made in Germany. However, untreated greywater cannot be used as flush-water as it will start to smell and discolour the flush toilet fixture if left for a day or more.

The level of treatment required in this case requires the water to have low or nil biochemical oxygen demand (BOD), but it is not necessary for it to be treated to the same standards as potable water. Greywater recycling for toilet flushing is currently considered to be uneconomical or environmentally unfriendly at most domestic levels. However, a Quebec company, Brac Systems, has recently patented a cost-effective system that uses a chlorine treatment, and is selling the system in the Americas, Europe, and Australia.

Extreme living conditions
Greywater use promotes the ability to build in areas unsuitable for conventional treatment, or where conventional treatment is costly. The Mars Desert Research Station utilises greywater recycling for this use, and might be used on trips to Mars to reduce water consumption and increase oxygen generation.

Heat reclamation
Devices are being developed which capture heat from residential and industrial greywater, through a process called "Drainwater Heat Recovery" or "Greywater Heat Recovery." Rather than flowing directly into a water heating device, incoming cold water is first pumped through a heat exchange in which it is pre-warmed by heat from greywater flowing out from such activities as dishwashing, or showering.

Greywater and the environment

The potential ecological benefits of greywater recycling include:

  • Lower fresh water extraction from rivers and aquifers

  • Less impact from septic tank and treatment plant infrastructure

  • Topsoil nutrification

  • Reduced energy use and chemical pollution from treatment

  • Groundwater recharge

  • Plant growth

  • Reclamation of otherwise misdirected nutrients

Move towards Ecologically Sustainable Development

Because greywater use, especially domestically, reduces demand on conventional water supplies and pressure on sewage treatment systems, its use is very beneficial. In times of drought, especially in urban areas, greywater use on gardens or in toilet systems helps to achieve Ecologically Sustainable Development by helping to meet its principles.

Dangers associated with Greywater use

When treated properly, greywater is of sufficient quality to use on gardens and landscapes but it is important to remember that greywater contains impurites and microorganisms that are capable of causing disease and illness.

A recent study carried out by the Queensland Department of Natural Resources, Mines and Energy covering the quality of domestic greywater found that greywater has organic strength and harmful organisms equal to and in some instances greater than toilet waste.

Many substances used for cleaning and washing are designed to be treated in a sewage treatment plant. The term "biodegradable" means the product is able to be degrade in a wastewater treatment plant where the established bacterial community will quickly metabolise these compounds. However, such substances will still degrade elsewhere, but the timeframe may be longer. Laundry wastewater can contain harmful organisms such as E.coli and diseases such as Hepatitis, which can remain in the correct ground conditions for extended periods of time. In general, it is difficult for human pathogens to remain viable for long periods in the soil, owing to the existing competitive bacterial community.

Uncontrolled release of greywater, with its associated nutrient load, could find its way into storm water drainage systems and streams causing algal blooms and disruption of ecosystems.

Importantly, sensible precautions can mitigate almost entirely the risk associated with greywater use. In order for disease transmission, people have to contact (by aerosol or directly) the greywater. If the greywater is applied by dripper systems or by subsurface delivery, this cannot occur. Avoiding greywater use, particularly by spraying, on vegetables eaten raw is recommended.

Tips on how to minimise health risks associated with greywater

  • Wash your hands after contacting greywater.

  • Install signage around greywater irrigation systems or areas.

  • Do not drink or play with greywater.

  • Do not allow anything that may be eaten to come into contact with greywater.

  • Do not allow greywater to pond or run off the property.

  • Do not wash domestic pets in greywater or allow pets to drink greywater.

  • Do not use greywater in public places such as children's play areas or playgrounds, BBQ areas or recreation facilities.