Managing Gray Water

Gray water is the water from the sinks and showers in an RV or the water from dishpans and wash basins when tent camping.   Gray water is usually just soapy water, but dishwater can often be quite greasy and contain quite a bit of food residue.  The question of dumping gray water on the ground comes up frequently.   Tent campers often just toss their dishwater or wash water out in the bushes or dump it on the grass.   This really isn't a good idea since soap and other contaminates can damage the environment and sometimes spread disease.  Never use this method if it is prohibited in the campground.  When you are allowed to use this method, such as when boondocking in a remote location, don't dump it all in one place.   Spread it out so it can filter through the soil before entering any aquafiers in the ground.   I've seen people camping in RVs in the desert run a garden hose 25-50 feet from their RV and let the gray water drain out onto the ground or into a gopher hole or snake hole.  Neither of these is a good idea and is often illegal.   Allowing it to flow out onto the ground will usually result it soapy residue after the water evaporates and soaks into the ground.  Running into a hole may flood some animal's home.  That might force dangerous animals like poisonous snakes out into your camp site!   All that being said, the technique is useful for extending your stay in a remote location -- IF  you can do it discreetly and legally.  If you feel you MUST drain gray water out into the desert, be sure to run the hose away from the camp so it doesn't flow back toward any occupied areas or create any muddy "traps" where campers might walk or vehicles might sink in -- and always make sure it isn't prohibited by local regulations to prevent damage to the environment and avoid costly fines.

The general rule, is only dump holding tanks (both gray and black) into approved dump stations.  In many jurisdictions it is illegal to dump ANY holding tank waste onto the ground.  Even in remote locations, like the desert camping described above, it is unwise to dump gray water onto or into the ground.  At the least you will likely be leaving residue that will create an unpleasant or offensive smell near your camp site.  Another camper may end up parking or setting up a tent on top of your discharge.  Next time you visit the area it might even be you!  Some campgrounds have special places called sumps for tent campers to dump their waste water.  They are often partially submerged perforated 55 gallon drums beneath a gravel covered dumping basin with sand and gravel in the bottom so the waste is contained and filtered before entering the eco-system.  These are adequate for small amounts of water like a dishpan or wash basin full of soapy water but should NOT be used to empty RV gray water holding tanks, which would overwhelm the capacity of the sump and probably overflow onto the surrounding ground.

The best way to limit how quickly your holding tanks fill up is to limit your water usage, which also helps your fresh water last longer.  Be stingy in your water usage.  Don't let it run to rinse dishes. Wipe them off with a paper towel or wad of old newspaper.  When you take a shower, catch the water you run while adjusting the temperature into a dishpan and use that for rinsing dishes and other routine cleanups around camp.  When washing your hands and face, brushing your teeth, or showering, turn off the water when you aren't actually using it to wet or rinse your body.   If your RV shower doesn't have a shut off at the shower head one can usually be added fairly easily and inexpensively.  Sometimes you can drain off little grey water into a bucket and use it to drown the campfire to reduce filling the holding tank.  The heat of the campfire plus the filtering effect of the ashes helps purify the water before it enters the ground.  Don't run a hose from your dump valve and drain your whole tank onto the fire.   It will probably quickly overrun the fire pit and contaminate your campsite.  If do run a hose to drown the campfire, make sure you have a shutoff valve or have someone monitoring the dump valve to shut if off as soon as the fire is out so you don't flood the area around the campfire with potentially smelly water.

Gray water tanks may develop foul odors if not properly maintained but usually proper flushing is all that is needed to keep them fresh and clean.   Chemicals can be added to further reduce odors if necessary.  There are chemical treatments especially designed for gray water tanks but, in an emergency, you could use a reduced amount of the same chemicals you use in your black water tank. Since you have no access to use a wand to flush gray water tanks, you either have to run sufficient water down the drains to refill and rinse the thanks, use a back-flush system on your dump hose, or use an "EZ-Flush".   The EZ-Flush is by far the easiest to use and the most effective.  It consists of a permanently installed nozzle on one of the walls of the holding tank that is connected to an external female hose fitting like your city water connection on the side of your RV.  You simple hook up a garden hose, turn on the faucet, and flush the tank until the water from the dump hose runs clear. Water from the gray water tank will usually be, well, gray or cloudy until it has been thoroughly flushed.  Being careful what you put into your gray water tanks is another way to avoid odors.   Avoid odor-causing deposits by NOT rinsing excess food from dirty dishes down your sink drain.  Use paper towels or old newspaper to wipe the garbage off instead of rinsing them in the sink.   Most soapy water, like from doing dishes, bathing, or washing your hands and brushing your teeth won't be a problem.  In fact, the soapy water will actually help clean the holding tank and the dump hose after dumping the black water tank.  Be cautious changing diapers and cleaning baby bottoms. You don't want fecal matter in your gray water tank!  It is surprising how little it takes to foster a bad smell.  Odors are more likely to develop in warm weather than cool so you might be more likely to need gray water odor treatments during hot summer camping trips.

You might get odors from your holding tanks while driving.   This is usually caused by a partial vacuum inside the coach generated by an open window.  It may also be caused by a clogged vent (birds and other pests sometimes build nests inside the vent caps on the roof).   If the odors are strongest inside a kitchen cabinet the problem may be a faulty vacuum breaker.  This is a device in the gray water plumbing that prevents the water seal in the P-traps being siphoned out when the tanks are dumped.   Sometimes tapping the device lightly will release a stuck valve, but don't hit it too hard. It is made of plastic and if you break it you'll have far worse problems than bad odors.  Speaking of P-traps, every sink and shower should  have one.  Its purpose is to trap water in order to prevent fumes and odors from the holding tank from coming back up and out of the drains into the living space.  If your RV hasn't been used in a while, the P-traps may have dried up.  Sometimes the water in the trap is sloshed out when driving on rough or twisty roads.  If you detect odors coming up from a drain, dump a cup of water down the drain to refill the P-trap.

Annual gray water tank cleaning.  Spring cleaning, when you de-winterize your RV and get it ready for a new season, is an excellent time to give your gray water tank a thorough cleaning.  Here is one way to easily do it.  Dissolve 2 cups of powdered water softener in 1 gallon of hot water and pour it down a drain in your RV.  Powdered water softener is found in the laundry section of the grocery store.  Pour 2 tablespoons liquid dish washing soap down the drain.  Run the water in your camper until the gray water tank is three-quarters full.  Drive the RV around for a few minutes to agitate the solution in the tank, then drain and flush it completely.  Thoroughly clean the gray tank in this manner at the beginning of each season and thorough flushing at each regular dumping should be sufficient to keep your gray water tank from going sour on you.  Often the water that enters the tank while flushing and sanitizing the fresh water system will be sufficient to clean and sanitize the gray water holding tank, but if  you still suspect odors after draining off the bleach solution used to sanitize the fresh water system, clean the gray water tank as described above.

Proper dumping and cleaning of holding tanks can help keep the sensors clean so you get accurate readings on you gauges on the monitor panel inside.

Daily odor control.   If you start to notice odors from your gray water tank, add a cup of vinegar through one of the drains for each 10 gallons of water in the tank.  Note, this is not for each 10 gallons of capacity, but each 10 gallons in the tank.  For example, if you have a 60 gallon tank and it is half full in will contain 30 gallons of waste water: add 3 cups of vinegar.   Vinegar is a safe and natural disinfectant that kills germs and reduces odors.  You will need to run a little water in each drain to flush the vinegar past the P-traps.

Gray water is mostly water and is susceptible to freezing when temperatures drop below 32° F.   It may resist freezing until a few degrees cooler, depending on the type and concentration of detergents and other stuff in the water.  If you are camping or just storing your RV in sub-freezing temperatures, you must takes steps to prevent the gray water system from freezing.   Exposed pipes can be wrapped with heat tape (assuming you have 120 volt power available).  Drain pipes and dump valves can be protected with antifreeze.  About a gallon of antifreeze added to an empty tank should fill and protect the dump valves.  You may need a lot more to keep the contents from freezing if  you're camping in sub-freezing weather.   See your local RV shop to determine how much antifreeze you need for the size of your tanks.  Dump at least 1-2 cups of antifreeze down every drain to protect the P-traps if when the interior isn't heated.  Without protection your gray water tank and plumbing could freeze solid and split.  When things warm up, the contents will leak out making a heck of a mess!   Always use the special, pink-colored, Marine/RV antifreeze.  Regular green, orange, or blue car engine antifreeze is toxic.

Read more: How to Remove Gray Water Tanks on an RV for details on how to replace a gray water tank that is no longer serviceable.  Any significant physical damage would make a tank unservicable.  A tank that has accumulated too much residue inside may be so difficult to clean that it can no longer be used.  Doing proper cleaning on a regular basis can prevent this from happening.

Keep it clean!