Cisterns and Grey Water

Catch tanks reduce the watershed that currently overloads our municipal sewers and storm-water drainage

The so-called "green" harvesting of roof-shed rainwater or Grey Water with above-ground rain barrels or underground catch tanks reduces the watershed that currently overloads some of our municipal sewer and storm-water drainage systems. Still, could we do the same thing by installing underground cisterns similar to those used during the 1800's and early 1900's?


Description of the earlier cisterns

Many older homes and estates today still have the remnants of their early underground rainwater cisterns. These fairly large, round, water-tight, root-free, 500-to-5000-gallon cisterns were made from brick, stone, rock, plaster, concrete, or combinations of these materials. They were each capped with an above-ground manhole-type of opening large enough to take a big bucket. This opening allowed the cistern to be periodically cleaned-out and repaired by the owner or by a third-party service.

The tin or zinc-plated guttering used on the house eaves then, which carried the rainwater down to the cisterns, were open and not covered. So, quite a bit of wind-blown tree leaves and seeds, and other debris could make their into the cisterns. For that reason, the suction end of the iron plumbing was located above the cistern floor, where the debris would eventually settle.

This relatively clean, soft, outside water supply was plumbed directly to the long-handle hand-pumps installed at the kitchen and bathroom sinks and the bathtub in the main house. It was also plumbed to the hand-pump in a small building behind the house that served as a summer kitchen and a place to wash laundry, to can garden produce, and to butcher chickens and hogs. This water supply remained relatively cool and unfrozen the year around. Generally, it was used for cooking, washing dishes, cleaning, canning, butchering, and bathing. But it could be drunk, too, after boiling it.

Modern cisterns

Modern cisterns operate much like the ones described above. However, instead of being built into the ground from scratch, they are buried prefabricated ones instead. That is, these cisterns could be prefabricated concrete receptacles, or they could be large prefabricated heavy-duty plastic tanks capped with fairly large screw-on tops, similar to the ones seen on certain lawn-treatment trucks.

Also, today's aluminum, steel, plastic, or copper eave gutters will have porous or solid coverings. Thus, the amount of debris entering the cisterns from the rooftops will be minimal. Yet, the fine sand-like material shed by asphalt or composite shingles will need to be filtered out early during the harvesting process; or else, it will eventually have to be removed from the buried cistern. The plumbing for the modern cistern will be heavy plastic pipe. Of course, the pump itself will probably be an electric one, its size and accessories will depend on how the harvested water is used.

More-than-likely, because most of us already have reliable purified municipal indoor drinking and bathing water supplies, this cistern water will be used for outdoor purposes, like, for the sprinkling of lawns and gardens, for filling fish ponds and small treated swimming pools, for watering trees and animals, and for washing vehicles, driveways, patios, decks, and houses. The following three advantages of the modern buried cistern system suggest this technology will work well today: 1) they are hidden from view and out-of-the-way by being underground, 2) they do not foster the production of algae or mosquitoes in the summer time, and 3) they help conserve the municipal storm-drainage systems and drinking water supplies.

Grey Water

Most of the world’s aquifers are being pumped faster than replenished, and all reservoirs are slowly diminishing in capacity as they fill with sediment. At the same time, natural surface waters and ground waters are being degraded by the wastewater continually dumped into them. Grey water reuse enables you personally to do more with the same amount of water and to increase your water security. At the same time, your grey water reuse reduces the problems of supply and pollution for everyone.

Any grey water system will realize some benefits, but obtaining all the potential benefits is trickier than it seems.

What Is Grey Water?

  • Grey water is laundry, shower, sink, and dishwater. It may be reused for other purposes, especially landscape irrigation.
  • Save freshwater by irrigating with household wash water
  • Relieve strain on your septic tank
  • Purify wastewater better without energy or chemicals

Any wastewater generated in the home, except water from toilets, is called grey water. Dish, shower, sink, and laundry grey water comprise 50–80% of residential “wastewater.” Grey water may be reused for other purposes, especially landscape irrigation.

Toilet-flush water is called Blackwater .

Wastewater without added solids, such as warm-up water from the hot water faucet, reverse-osmosis purifier drain water, or refrigerator compressor drip, is called clear water.

Reclaimed water is highly treated mixed municipal grey water and black water, usually piped to large-volume users such as golf courses via a separate distribution system.

What Can You Do with Grey Water?

Conventional plumbing systems dispose of grey water via septic tanks or sewers. The many drawbacks of this practice include overloading treatment systems, contaminating natural waters with poorly treated effluent, and high ecological/economic cost.

Instead, you can reuse this water. The most common reuse of grey water is for irrigation. It can also be cascaded to toilet flushing or laundry. Even a grey water disposal system has less negative impact than septic/sewer disposal.

Why Use Grey Water?

It is said that there is no such thing as “waste,” just misplaced resources. Grey water systems turn “wastewater” and its nutrients into useful resources. Why irrigate with drinking water when most plants thrive on used water containing small bits of compost?

Unlike many ecological stopgap measures, grey water use is part of the fundamental solution to many ecological problems. It will probably remain an essentially unchanged feature of ecological houses in the distant future. The benefits of grey water recycling include:

  • Reduced use of freshwater—Grey water can replace freshwater for some uses. This saves money and increases the effective water supply, especially in regions where irrigation is needed. Residential water use, on average, is almost evenly split between indoors and outdoors. Most water used indoors can be reused outdoors for irrigation, achieving the same result with less water diverted from nature.
  • Less strain on septic tanks or treatment plants—Grey water, which comprises the majority of the wastewater stream, contains vastly fewer pathogens than black water and 90% less nitrogen (a nutrient that is a problematic water pollutant). Reducing a septic system's flow by getting grey water out greatly extends its service life and capacity. For municipal treatment systems, decreased flow means higher treatment effectiveness and lower costs.
  • More 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. Topsoil is a purification engine many times more powerful than engineered treatment plants, or even in septic systems, which discharge wastewater deeper into the subsoil.3
  • Feasibility for sites unsuitable for a septic tank—For sites with slow soil percolation or other problems, a grey water system can partially or completely substitute for a costly, over-engineered septic system. (In extreme cases this can enable otherwise undevelopable lots to be built on—a double-edged sword environmentally.)
  • Reduced use of energy and chemicals—Due to the reduced amount of freshwater and wastewater that needs pumping and treatment. If you provide your own water or electricity, you’ll benefit directly from lessening this burden. Also, processing wastewater in the soil under your fruit trees definitely encourages you to dump fewer toxins down the drain.
  • Groundwater recharge—Grey water application in excess of plant needs recharges the natural store of water in the ground. Abundant groundwater keeps springs flowing and trees growing in intervals between rains.
  • Plant growth—Grey water can support a flourishing landscape where irrigation water might otherwise not be available.
  • Reclamation of nutrients—Loss of nutrients through wastewater disposal in rivers or oceans is a subtle but highly significant form of erosion. Reclaiming otherwise wasted nutrients in grey water helps to maintain the land’s fertility.
  • Increased awareness of, and sensitivity, to natural cycles—The grey water user, by having a reason to pay more attention to the annual progression of the seasons, the circulation of water between the Earth and the sky, and the needs of plants, benefits intangibly but greatly by participating directly in the wise husbandry of vital global nutrient and water cycles.
  • Just because Grey water is relatively harmless and great fun to experiment with. Moreover, life with alternative waste treatment is less expensive and more interesting...


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