Grey and black water


Water Saving: Grey & Black water – There has been a lot of publicity around Grey water systems in recent weeks, we will cover the main points.

The average suburban garden accounts for about 46% of domestic water consumption. Some municipalities charge you for the water you use and then charge 70% of the water as sewerage – whether it goes into sewerage or not. So if we can reuse some of our water we get a double saving.

There are 2 types of reusable water in the domestic environment namely Grey and Black. Black water being from toilets & urinals and Grey from all other sources, some pundits even further classify grey into bad grey water and good grey water. Good being from Baths, showers and washing machines and bad from sinks and dishwashers. Black is best left to go through the sewerage system; although there are systems to reuse black water; mostly on fruit trees.

Grey water systems can be as simple as leaving your bathwater in the bath and using to flush toilets and water the garden; or, you can catch your shower water in a bucket and do the same. Grey water systems can be DIY valve installations to divert water; right up to sophisticated systems with pumps, filters, storage and solar powered.

Grey water, if untreated, should not be used for drinking or cooking, unless it has passed through a purification system that has been certified and is regularly maintained and checked, it’s better left for other domestic purposes, such as flushing toilets and watering the garden. Do not use grey water in your swimming pool or ponds.

Grey water systems generally do not store the water; they tend to use the water immediately on the garden. It is not recommended to use water that has been in the greywater filtration system for more than 24 hours or bacteria builds up, affecting the water that is being reused. Most of the concerns about grey water are to do with the hygiene aspect and odours of the water, but both these aspects are eliminated if the water is re-used as soon as possible and bacteria has not been given the time to reproduce.

A household of 4 will use between 150 and-300 litres of reusable water daily. At low usage levels (less than 50l per day) a sophisticated grey water system will not be economical; but, you can still use if doing the right thing is important to you.

Be careful of using your kitchen water as this can be damaging to plant life because of the fat content; wipe fat off or better yet let your dog’s remove it. Dishwasher water containing salt and “Sun” should never be used in a greywater system. Hair conditioner can clog the system if heavily used.

It is advisable to use biodegradable products where possible. The residues and soaps etc in the water in diluted quantities can provide useful sulphates and nitrates; that are commonly found in garden fertilizers. Some experts say grey water is more beneficial to the garden than clean tap water; it boils down to the type of plants you have and their tolerance of the substances found in your particular grey water

In any grey water system, it is important to avoid toxic materials such as bleaches, bath salts, artificial dyes, chlorine-based cleaners, strong acid/alkali, solvents and products containing boron, which is toxic to plants at high levels. Most cleaning agents contain sodium salts, which can cause excessive soil alkalinity, inhibit seed germination, and destroy the structure of soils by dispersing clay. Soils watered with greywater systems can be amended with gypsum (calcium sulfate) to reduce ph.

Cleaning products containing ammonia are safe to use, as plants can use it to obtain nitrogen. A 2010 study of greywater irrigation found no major health effects on plants, and suggests sodium buildup is largely dependent on the degree to which greywater migrates vertically through the soil. Rather investigate the use of cleaners such as Bicarb, vinegar and lemon juice.

It is recommended that you move the hose around to spread the grey water across the garden. Irrigating with potable water, if available and allowed, occasionally, is recommended. If you wish to use through your sprinkler system talk to a professional first, not all irrigation systems are compatible. Keep in mind that you may not have enough to water the whole garden – in particular your grass. Plan ahead as to what parts you can save and what is best left to cope by itself.

Recycled grey water can be used on your vegetable garden, but is not recommended two weeks before harvesting.The water left over after you’ve washed your car is also considered grey water. Recycling car wash water is probably the easiest way to recycle water because all you have to do is slosh it over your lawn.

Be patient as right now the professional installers are very busy.

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