Get ready to save water by prepping for a grey water system this winter. Regardless if you want to save water or not, use grey water to help your garden thrive-be more productive.
The "dirt" in grey water (GW) is also its nutrients. In reality, filtering GW for a drip-irrigation system is counterproductive. Unfiltered GW can increase the yields of plants up to 20%.
|Here is a greywater system hidden in the home's crawl space. It captures the water from the bathroom sink, shower and bathtub. (Not the laundry.) This is an illegal system in California (but it's way out on the woods - however, just using laundry water is legal in California without a permit). It feeds the drip irrigation system rather nicely. The white valve allows you to shut the tank off and divert the greywater to the septic tank or sewer. The upper black pipe is the overflow if too much water comes into the tank at once.
In a study in South Africa, studies of carrots, "beetroot," spinach, and peppers grown with GW, nutrient solution, and tap water always showed a considerable increase in the yields with GW when compared to tap water. The nutrient solution plants always had the greatest yields, but the GW plants had "...yields similar to that obtained when using chemical fertilizers." Furthermore: "Grey water-irrigated produce is likely to be safe for human consumption [based on microbiological analyses.]." Notice that two of the crops analyzed were root crops.
(Greywater Use for Agricultural Irrigation in Urban and Peri-Urban Areas,
Lumka Salukazana, S. Jackson, N. Rodda, M. Smith, T. Gounden, N. Macleod
University of KwaZulu-Natal; eThekwini Municipality, South Africa.)
Another study, at Texas A & M University, surveyed the yields of vegetables (tomatoes, bell peppers, and jalapeño peppers.) and cotton irrigated with GW compared to those irrigated with brackish water. The quantity of vegetables produced increased by 20%. Cotton that was mulched and then irrigated with GW produced 70% more cotton fiber (lint), when compared to conventional plantings with no mulch and irrigated with brackish water. In the end, they found that: "Cotton plants irrigated with graywater grow better than those irrigated with freshwater."
(Use of Graywater and Brackish Water for Cotton and Vegetable Production, ZhupingSheng, Ph.D., P.E., 2010)
Still, the prudent person will avoid using GW with annual ornamental bedding plants or vegetables that touch, or grow in, the soil, especially those that require working the soil several times per season. The safest use of GW is in a well-designed landscape planted with perennial shrubs and trees that will not be moved or be replanted, or with fruit trees, being sure that you don't eat any fallen fruit.