What is Greywater? – FAQs

What the hell is greywater?

Greywater is technically household wastewater from the laundry (including the washing machine and tubs) and the bathroom (including showers, baths and basins). Toilet water and kitchen wastewater are regarded as blackwater and are not suitable for reuse in domestic gardens, due to the potentially high levels of bacteria, fats and solids contained in this wastewater.

“The diversion of greywater from the house and into the garden has become an extremely popular way of irrigating our precious green spaces in these times of low rainfall and water restrictions When done correctly, it is an excellent way of saving water and money. It is amazing to think that one average household (2.5 people) expels 124 100 litres of greywater a year! (from www.westernwater.vic.gov.au) That’s more water than most established gardens need in the same period. And, unlike rainwater, greywater is available all year round, regardless of the weather!” (Courtesy of www.envirofriendly.com)

Greywater is great… an awesome resource that, when used correctly and cleverly, can prevent our precious drinking water from being dumped into garden beds.

Is grey water reuse safe?

Yes. There are eight million greywater systems in the US with 22 million users. In 60 years, there has been one billion system user-years of exposure, yet there has not been one documented case of greywater transmitted illness. Source www.oasisdesign.net

The benefits of grey water recycling (in detail)

  • Lower fresh water use

Grey water can replace fresh water in many instances, saving money and increasing the effective water supply in regions where irrigation is needed. Residential water use is almost evenly split between indoor and outdoor. All except toilet water could be recycled outdoors, achieving the same result with significantly less water diverted from nature.

  • Less strain on septic tank or treatment plant

Grey water use greatly extends the useful life and capacity of septic systems. For municipal treatment systems, decreased wastewater flow means higher treatment effectiveness and lower costs.

  • Highly effective purification

Grey water is purified to a spectacularly high degree in the upper, most biologically active region of the soil. This protects the quality of natural surface and ground waters.

  • Site unsuitable for a septic tank

For sites with slow soil percolation or other problems, a grey water system can be a partial or complete substitute for a very costly, over-engineered system.

  • Less energy and chemical use

Less energy and chemicals are used due to the reduced amount of both freshwater and wastewater that needs pumping and treatment. For those providing their own water or electricity, the advantage of a reduced burden on the infrastructure is felt directly. Also, treating your wastewater in the soil under your own fruit trees definitely encourages you to dump fewer toxic chemicals down the drain.

  • Groundwater recharge

Grey water application in excess of plant needs recharges groundwater.

  • Plant growth

Grey water enables a landscape to flourish where water may not otherwise be available to support much plant growth.

  • Reclamation of otherwise wasted nutrients

Loss of nutrients through wastewater disposal in rivers or oceans is a subtle, but highly significant form of erosion. Reclaiming nutrients in grey water helps to maintain the fertility of the land.

  • Increased awareness of and sensitivity to natural cycles

Grey water use yields the satisfaction of taking responsibility for the wise husbandry of an important resource.

But I’ve heard greywater use is bad for plants… is that true?

Rresearch regarding the long-term impacts of greywater on plant and soil health is lacking, so the affects of usage are, at this stage, a bit of an unknown quantity. If you are irrigating sensitive plants, consider feeding rainwater into the system, which will dilute any potentially harmful effect. Monitor plants and if you notice leaves discolouring, move the dripper line further from the stem allowing the soil to filter any contaminents before absorption.
Remember, the quality and performance of greywater irrigation can vary dramatically, dependant on a number of factors. These include -

  • the type of greywater used (eg: washing machine vs. bathwater)the types of chemicals included in greywater (eg: soaps and washing powders)
  • the irrigation method
  • the type of plants being watered
  • the length and duration of watering
  • the soil structure and type
  • the presence of soil organic matter and so on.
  • That said, there are some straight forward ‘do’s, don’ts’ and ‘no-you-didn’t’ regarding greywater and these have been popped together in an easy to use reference chart.

Talking Phosphorus

With that in mind, it is always preferable to choose a detergent that contains low or no phosphorus if you are irrigating with greywater. This will avoid any detrimental affects to soil health and plant health, both in your backyard and beyond the back fence Phosphorus sensitivity is a particular issue with members of the Protea family (Proteaceae) which includes Banksia, Grevillea, Hakea and Isopogon. However, phosphorus sensitivity varies and it should not be assumed that all native plants will not tolerate phosphorus.

Low phosphorus detergents must be used in any long-term application of grey water from laundry sources, regardless of the phosphorous sensitivities of plants or not. Excessive phosphorus is unable to be taken up by plants, and has the potential to damage soil structure, as well as leaching into our groundwater, and polluting our rivers.

What do I do with all this water?

The biggest issue faced by gardeners irrigating with untreated greywater is not necessarily the quality of the water, but the amount of it and frequency at which it is being applied. Put simply, people are watering more than they ever did and are literally drowning their plants and their soil. Please, check your soil moisture before irrigating. If the soil is damp, direct your greywater to the sewer, rather than to the garden! Greywater cannot be stored for longer than 24hours, so, if you don’t need it, divert it!

Give your soil time to recover

All soils under greywater irrigation should be allowed freshwater and the best time for this is through winter, when less water is required and Port Elizabeth historically receives highest monthly rainfall between May and September! Having said this, your systems must be able to divert the greywater away from the tank, not through it!

What about the water from my bathroom?

On average, a two to three person household generates 185 litres of greywater per day from the hand basin, shower and bath. The chemical constituents of bathroom greywater include soap, shampoo, hair dyes, toothpaste and cleaning chemicals. Greywater from hand basins is more polluted than bath or shower greywater, but is much lower in volume. If hair dyes and cleaning chemicals are being utilised, divert the greywater to the wastewater rather than the garden.
I get asked quite often how the use of soaps and shampoos will impact the quality of greywater used for garden irrigation. Generally speaking, the amount of soap and shampoo used in the shower is quite minimal, and pretty well diluted by the time it gets out to the garden. Most of it is biodegradable, and is unlikely to have any significant long-term impact on the plants and soil.
Never take water from the kitchen – kitchen’s use toxic detergents and it is always good to have an outlet directly to sewer so that if you do need to use toxic detergents, you can pour them down the kitchen sink and divert them away from your garden

Do’s and don’ts of greywater?

  • Do consider a professionally installed, fail safe greywater treatment system – saves you time, stress and effort.
  • Do monitor your soil – check pH, smell, “life forms” eg worms, bugs etc.
  • Do monitor your irrigation needs – if it doesn’t need water, don’t water it!!!!!
  • Do disperse the water subsurface – either on top of soil and under mulch, or trenched into soil – it’s better for your plants!.
  • Do allow your garden a rest from greywater – turn it off in times of high rainfall or winter months when irrigation isn’t needed!
  • Do think carefully about the products you use inside the house, and what affect that will have outside eg: disinfectants, hair dye, bleach, cleaners
  • Do restrict greywater use to your garden – untreated greywater is not suitable for washing cars, hosing down paths, washing windows etc.
  • Do filter out as many solids as you can.
  • Don’t store untreated greywater for over 24hours.
  • Don’t water just because the greywater is there – you’ll drown your plants and your soil, so switch off during periods of high moisture.
  • Don’t water your vegie patch with greywater!
  • Don’t shandy greywater with rainwater in a storage tank or similar (for more than 24 hours) – you still can’t store it, and you run a serious risk of harbouring bacteria
  • Don’t allow pets or people to play in pooled greywater.
  • Don’t allow atomizing of greywater use sprinkler systems that operate under low pressure but – preferably disperse your greywater directly to soil or under mulch – greywater sprinklers are illegal in many countries!
  • Don’t use kitchen water or toilet water – this is pretty obvious
  • Don’t let greywater wash into your neighbours yard or neighbouring properties – nothing says neighbourhood dispute like your waste water in the yard next door

Relating to greywater systems

How much space do I need, am I going to have an unsightly tank in my garden?

The Water Wizard system is needs less than 1M² of space and is installed underground. Depending on the system, all you see is the top of the filter and the top of the tank, both of which can be easily concealed.

What about the waste pipes?

The answer to this question is site specific and depends on location of pipes, distance to tank etc, but generally they will not be any more unsightly than you current piping. However, in new houses, pipes can easily be concealed.

What about the irrigation pipes?

Supply pipes to your sprinklers or to your dripper system can generally be placed under ground, but as a rule of thumb, the system will be no more visible than a conventional main supply irrigation system.

What about my existing irrigation system?

Your greywater system cannot be connected to your conventional system for 2 reasons:

  1. Greywater must never be allowed to atomise – this, quite simply, is unhealthy.
  2. Conventional systems will block in a matter of days if used for greywater.

Go-green suggests that you leave your existing system in place – just switch it off. Greywater gardens need brief periods of respite from greywater so they can ‘de-tox’ and in times of plentiful supply, your existing system can be activated for 2 or 3 weeks to fulfill this function.
Go-Green will provide a complete new system for your greywater.

Can I supplement greywater with rain water?

Yes you can, Go-green will discuss this with you on site – but remember you are supplementing grey water so you still cannot store it.

Is the greywater filtered?

  • In all instances, it is essential to have a primary filter that removes hair, lint and any solid that may damage the pump.
  • In basic sprinkler systems, no further filtering is required, although you may request a filter in the line for added protection and water cleanliness, but this is not necessary.
  • In dripper systems, a secondary, 130micron filter is fitted in the line to ensure that drippers never block.

Does the grey water give off an odour?

This depends on the system being used.  Grey water does produce an odour while irrigating if using the sprinkler system, but the odour disappears within seconds after irrigating. However, if using the Water Wizard Dripper system, the odour can only be smelt if you put your nose within 500mm of the drippers and then only when they are dripping.

How many bathrooms can I connect to the system?

The more the merrier, however if more than four or if you have a busy laundry (guesthouses), then it may be better to fit 2 systems and direct them to entirely different areas of your garden – remember, over watering is as dangerous as no watering!

Where does Go-green’s installation start and end – do I need to employ other contractors for different aspects of the installation?

Go-green will complete the entire installation from the point of water collection to water delivery, no other input is needed.

How long does the Water Wizard take to install?

This is dependant on the system purchased, generally in a day, but never more than 2 days

How much does the Water Wizard grey water system cost?

Prices are dependant on system chosen and subject to site specifics. You will be given a quote, but as a rule of thumb, the cost of a fully installed system costs between R6,500 and R10,000.

My fresh water system requires absolutely no work – does this apply to the Water Wizard system?

This is a complex question to answer.

  • Firstly, the Water Wizard primary filter, because of its self cleaning properties only requires 10 minutes every 2 weeks. This filter, unlike most others, doesn’t not need to be removed and cleaned by hand and you don’t have to worry about disposing of the accumulated hair.
  • Secondly, if you choose the sprinkler system, the sprinklers will need to be moved on a daily basis. If you choose the dripper system, this only requires 10 minutes every 3-4 weeks, to rinse the line filter and back-wash the lines ensuring that they stay open.