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This refers to any used water with a low level of contamination, and no exposure to feces, fats, or oils. This is the easiest and safest type of water to recycle. Common sources of grey water include:  Showers and baths Bathroom sinks (but never kitchen sinks) Laundry (but see below) Most laundry detergent contains high concentrations of sodium and chloride compounds. These make the water dangerous to plants. Switch to biodegradable detergent if you plan to recycle this water for your garden. Similarly, avoid using any cleaners that contain boron, bleach, or sodium in an area that leads to grey water collection. Ammonia cleaners are a safe substitute. Do not use liquid softener in the laundry, or detergent that advertise a softening effect. Switch to fabric softener sheets in the dryer instead. Grey water that comes from laundry machines can be contaminated with small microfibers that break off from the fabrics you wash. Microfibers are non-biodegradable and they're often coated with chemicals, so it's important that you filter them out of your grey water before you use it in your garden. You can also use a microfiber laundry ball to collect loose microfibers in your laundry machine. Do not wash anything in your shower, bathroom sink, or laundry that came into contact with gasoline, paint, mothballs, or other harsh chemicals. Also avoid washing oil or fat into these systems, as grease can clog soil and fail to drain. Water from laundry that includes diapers or blood-soiled clothing should never be recycled without professional treatment. This is "black water," or water that contains biohazards or other major health risks. This is the easiest way to get started recycling water. Just put down a bucket in the shower, or disconnect a bathroom sink trap and place a bucket under the opening. Although no serious health consequences have been traced back to grey water handling, health organizations recommend these precautions:  Never store untreated grey water for more than 24 hours, or bacteria can multiply to unsafe levels. Since an odor can develop within a few hours (especially with shower water), you may want to limit this to even shorter storage lengths. Avoid skin contact with grey water. Wear gloves while carrying the buckets. Pour the grey water directly into the toilet bowl to flush. Never pour grey water into the toilet tank, as this can backflow into the clean water supply, or clog the flushing mechanism. This pipe diverts grey water from your washing machine directly to 1 inch (2.5 cm) backyard tubing. This directs the water to several mulch-filled basins around your yard. This is not the most efficient way to irrigate, but it is one of the cheapest and easiest to set up.  Read the garden instructions below before you set this up. Install a filter in this system and clean it regularly. Instead of hauling buckets to your garden, you may alter your plumbing to automatically divert grey water to another purpose, usually a drip irrigation system in your garden. Here's a basic overview:  Check your local, state, and country laws. California in particular has strict permit requirements.  Keep grey water pipes clearly labeled and completely separate from clean water plumbing. Excess should drain into the sewage system, with a valve preventing backflow. To reduce the chance of clogs, use pipes with diameter 1½ to 2 inches (4-5 cm) and avoid U-bends. If you want to store your grey water for more than 24 hours, you'll need to have a plumber install a grey water treatment device. Due to expense, these are mainly used by businesses, but they are available for households. "Dark water" generally refers to waste water that's more difficult to recycle than grey water, but not outright unusable (that's "black water"). If you're in an area with a severely limited water supply, you may want to take advantage of this as well:  The kitchen is the most common source of dark water, containing grease, food contaminants, and powerful detergents from the dishwasher. At minimum, you will need to install a grease trap and filter before using this water in the garden. You may also need a treatment device to remove other contaminants. While the bathroom sink creates grey water, hooking it up to the dark water system can help flush through the particle-heavy water.
Identify grey water. Check your detergent and cleaning compounds. Install a microfiber filter if you want to use grey water from a laundry machine. Ban dangerous and greasy materials from your grey water. Gather grey water in buckets. Pour grey water into the toilet bowl. Consider a "laundry to landscape" pipe. Install an automatic grey water collection system. Consider a dark water treatment system.