Gray water (or graywater, grey water, sullage) is water that has been used for some non-sewage purpose, such as a shower or washing dishes. It may contain contaminates like food particles, soap, dirt, and grease. It has very limited further use and needs to be stored until it can be disposed of. It is not as contaminated as black water and is not considered sewage, but it may contain pathogens from human waste if, for example, the water was used to wash the anal area or used for laundering underwear.
Gray water can be held two ways:
- A holding tank for later dumping at a dump station. This is more common in commercially-built motorhomes, travel trailers, etc., where pipes run directly from the sink(s) and shower to an undermount tank.
- In portable water containers for later dumping in a residential or commercial toilet, dump station, or other appropriate location. This is more common in self-built conversions, where a sink drains into a container directly under the sink.
If using portable water containers to store your gray water, the most common receptacles are 5-to-7-gallon fresh water jugs. Don't mix up your fresh and gray water! Fresh water containers are typically blue, just as gasoline jugs are red and diesel jugs yellow. A jug with an upward-facing mouth may be easier to route water into. You'll likely want to use an RV sink trap and/or a fine-mesh sink strainer to keep food particulates out of your gray water to reduces unpleasant smells.
Gray water cannot generally be improved enough via water filtration and water purification for reuse as non-potable water, but systems are available for certain uses, like a recirculating shower which filters and cleans used shower water for reuse. If you have a flush toilet, gray water can usually be used as a flushing aid rather than fresh water.
Gray water tanks can be smelly! In some cases worse than a black tank. Putting a bit of mouthwash or bleach into your tank periodically will help control odors.[1]
Dispersed dumping
Some nomads will dump gray water over grassy areas, storm drains, or on roads. This practice, sometimes known as "stealth draining", is somewhat controversial, but with care it can be done in an environmentally acceptable way. Dispersed dumping is most acceptable if:
- Your gray water contains low amounts of biodegradable particulates, and no non-biodegradable matter.
- You do not dump a large amount of gray water in one place.
- You do not dump where others have recently dumped.
- You dump away from food sources, waterways, and other sensitive areas.
- If dumping on the ground, the wet spot will dry up before someone else walks through the area.
- If dumping where nuisance wildlife are attracted by food smells (such as bears), being sure to dump far away from campgrounds and other human-use areas.
- You are careful to comply with local dumping laws and any posted signage.
Straining your sink water (with a sink trap or mesh strainer) is particularly important if stealth draining to avoid unsightliness, reduce visible evidence, and avoid attracting flies and bears.
To increase stealth, when planning your build, put the tank drain where you can easily and stealthily release into grass (near back bumper, etc). Drain only at night to reduce the chance of being spotted and to give damp ground a chance to dry up by morning.
Some nomads have added an electric drain valve to their undermount holding tank which can be remotely opened while driving. This allows a small stream of gray water to flow out of the tank which is then spread across a long stretch of road. This method allows your water to have the least impact due to the large dispersal area, and low likelihood of bothering others.
In the United States, draining wash water on public BLM land is allowed in some areas but not others: "Although the Code of Federal Regulations (CFR) found at 8365.1-1 (3) generally excludes 'wash water' from BLM’s prohibition against draining or dumping, it can be specifically prohibited by Supplemental Rules issued for a specific area. This applies equally to RVers and tent campers."[2]
Resources
| Wikipedia: Gray water |
Some content on this page was originally sourced from RVWiki.
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