Greywater helps save a valuable resource

According to long-term weather forecasts, Greece is in for an early hot spring and a very long, hot and dry summer. Most water consumption (over 80 percent) – and waste – in Greece is in agriculture, but proper water management strategies emphasize limiting the amount of water wasted everywhere, and reducing demand. When water access is easy and cheap, people tend to use more than they actually need. In the US, average personal water use is nearly 600 liters per day, compared to about 50 liters per day in India. When droughts are at their worst, it almost seems criminal to pour good tap water into the soil. Gardeners in the Mediterranean have found ways to conserve water by preferring native plants adapted to drought conditions, but there are some days when even these need some water. One way is to save household water from showers, wash basins and washing clothes for use in the garden. This «greywater» is only mildly polluted, and it gets purified by the top layer of soil. Its use is restricted under current single-drain plumbing systems, but it is being made easier as more experience is gained and new techniques developed. Provisions for greywater drains need to be taken into consideration when a house is built; and it is therefore more appropriate for independent houses outside the city, where household water usually flows into a simple cesspit that has to be emptied every so often by expensive waste removal tanker trucks. It involves directing water from showers, wash basins and washing machines (that is, everything except the the toilet and the kitchen sink) to flow straight into the soil, which purifies it, and saves tap water for the house. Tests carried out by the British Consumers’ Association magazine have shown that fuchsias and runner beans performed equally well with both tap water and greywater. One group was watered twice a week with simulated greywater (shower, washing-up, washing machine and dishwasher water) and another with tap water. Advocates of greywater say its use restricts wastage of drinking water when plants can thrive just as well on used water. The upper, most biologically active layer of the soil purifies greywater to a great extent so that ground water is not polluted but recharged with any purified greywater that filters down into it. The greywater must pass slowly into the soil if it is to be purified. It should never be allowed to flow into saturated soil or in the vicinity of a well or spring. Plumbing methods for diverting the flow of greywater from the house are specific to each site. If the washing machine, for example, is in an outhouse, water outflow can be directed straight into the soil. However, you should be careful that no kinks develop in the hose, forcing the water back into the machine and burning out the pump, and that the water is not hot. Some experts recommend using a small drum to temporarily hold water that surges too rapidly for the hose, or is too hot; but greywater should not be stored more than a few hours or it will quickly turn into malodorous «black» water. (Remember what happens when water stays in the washing machine too long!) If a small intermediary tank is used, it should be designed to empty completely, not leaving even the smallest amount of water to get left behind and pollute subsequent flow. If you are planning to construct a greywater drainage system, it is wise to get expert advice for the particular site. There are several books on the subject (see box), but a few points that should be borne in mind can be mentioned here. Greywater hoses should be marked to differentiate them from tap water sources. They should not be used in sprinkler systems as the droplets can evaporate, leaving harmful microorganisms suspended in the air. Nor is it suitable for drip irrigation systems, as it would clog the drip holes. Greywater should not fall on foliage, including lawns, again because of the risk of human contact with bacteria. For the same reason, it is not suitable for vegetables that are eaten raw, such as tomatoes, lettuce, or other leafy vegetables. However fruit trees can be irrigated with greywater as long as it goes straight to their roots. In fact, some sources say the best way to use greywater is in a heavily mulched bed around trees. Good drainage and a downhill slope appear to be the most important factor. Greywater expert Art Ludwig says it is critical that the slope be at least one quarter inch per foot. Water used by anyone with an infectious disease should not go into the greywater system. Nor should one use harsh detergents such as chlorine to clean bathroom sinks and showers, but rather a milder detergent. Bill Mollison, the founder of Permaculture, suggests another use for shower and bathroom sink water; diverting it to the flush tank of toilets. However, his suggestion of getting the water into the cistern is somewhat impractical in most homes, as it would involve raising the shower and handbasin a few steps above floor level and using a low-level cistern. Guides to building the systems – «Create an Oasis with Greywater, Your Complete Guide to Choosing, Building and Using Greywater Systems,» Oasis Design Books. – «Branched Drain Greywater Systems, Reliable Sanitary, Low Maintenance Distribution of Household Greywater to Downhill Plants without Filtration or Pumping,» by Art Ludwig, Oasis Design Books. – Also by Art Ludwig, «The Builder’s Greywater Guide, Installation of Greywater Systems in New Construction and Remodeling.»

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