Managing RV Black Water

Black water is the term used to describe toilet wastes from an RV.   Black water isn't really black.  It is usually green, blue, or brown, depending on the type and amount of holding tank chemicals -- or lack thereof.  Doesn't really matter whether you have a motorhome, travel trailer, truck camper, or van conversion -- the process is pretty much the same.   Tent campers usually don't have any black water unless they are using a port-a-potty.   Dumping or spilling black water onto the ground is nasty and is NEVER permitted.   Black water should only be drained into an approved dump station or pumped into a proper sewer system.   The only way to manage black water accumulation in remote areas is to limit filling your black water tank or plan to drive to approved dump stations.  That means taking advantage of pit toilets or outdoor latrines as much as possible.  When the tank gets full, you'll need to go to a dump station or drain the tank into an approved portable holding tank for temporary storage and subsequent disposal.   Dealing with transporting temporary holding tanks any distance to a dump station is cumbersome.  Some people find it helpful to use them if the campground has a dump station but no sewer hookups in each site.   You can periodically drain black water into the portable holding tank and drag the portable tank to the dump station instead of having to disconnect everything and drive your RV.  Some of the larger portable tanks have wheels and are designed to be pulled by a motor vehicle.  When boondocking, you will have to either limit filling your holding tanks or take time to drive to an approved dump station before your tank fills.  If you wait until the sewage is backing up or the toilet won't flush, you'll have a really nasty mess to deal with.

If you consistently fill your black water tank, you might need to look for a different RV with a larger holding tank.  The big Class A rigs we used when the 6 kids were with us had 100 gallon black water tanks.  The Class C we downsized to had a 25 gallon black water tank.  In some cases, probably rare cases, you might be able to install a larger black water tank on your rig.  Available space on most RVs has already been used up one way or another.  You might be able to gain some black water capacity if you can sacrifice some exterior storage, but finding room for a second or larger holding tank on most rigs won't be very practical and could be expensive if there is room.  If you do modify your black water tank make absolutely sure is is adequately supported so it won't sag or fall out!

Use the right toilet paper.  There is a special grade of toilet paper designed for use in RV holding tanks and porta-pottys.  While ordinary household paper does the job, it is usually thicker and doesn't break down as easily as RV toilet paper, leading to difficulty dumping the tanks.  If you can't get RV toilet paper, use the cheapest, single-ply residential paper you can find.  It is likely to break down easier than the fancier, multi-ply brands.  Of course, be somewhat selective.  Remember the old poem:  "Roses are red, violets are blue;  Toilet paper's no good If your finger goes through"!  Avoid putting facial tissue in the toilet as it doesn't break down well either.  Never put paper towels or sanitary napkins in your RV toilet. They are almost sure to cause a clog or get stuck in the tank when dumping.  Even "flushable" baby wipes should be avoided.  They might be OK in city sewer systems, but not in RV holding tanks!

There is a simple test you can do to see if your toilet paper is suitable for use in an RV or porta-potty.   Put couple of sheets of toilet paper in a quart jar, fill it with water, shake it, and let it stand.  If the toilet paper breaks down within a few minutes it is OK to use it in your RV or porta-potty.  To see what  happens with toilet paper that doesn't break down, try the same test with a facial tissue.  It will probably retain its structure in the jar of water for days!

The other part of managing black water, besides limiting accumulation and dumping, is controlling odors and facilitating the break down of solid wastes.   This is controlled by the use of proper holding tank chemicals and making sure there is adequate liquid in the tank and dumping the tank as needed.   RV toilets usually use only about a quart of water or less per flush, compared with 3-5 gallons in a residential toilet so solid wastes can build up in the tank if there isn't enough liquid.   Some RVs drain shower water into the black water tank to increase the liquid to solid ratio.   If yours does, overfilling the black water tank will result in a very unpleasant and unsanitary back up into your shower!   Holding tank chemicals serve two functions:  1) they assist breaking down solids and 2) they control odor.   If your holding tank develops foul odors between dumpings you probably need to add more chemicals. You will normally need more chemicals in hot weather than cold.   Improper or inadequate dumping of holding tanks can also contribute to bad odors.  First of all, the tank needs sufficient liquid to flush out all the solid waste.   Normally, with proper chemical treatment, the solids will have begun to break down and will flush out easily.  Rinsing the tank after it has been dumped is necessary to ensure no residue is left behind to cause odors.  There are several ways to rinse the black water tank. The "old school" method is to use a "wand" attached to a garden hose.  The wand is put down through the toilet and is rotated so the jet of water coming out one side sprays around inside the tank to wash away any debris stick to the walls and roof of the tank.  Using a wand can be messy if you aren't careful to keep the spray aimed down inside the tank. If you pull it up too high, it will hit the down tube from the toilet and spray back in your face!   The water in the wand is probably clean, but what it picks up from the down tube can be nasty.  There are back-flushing devices that allow you to attach a garden hose to special connectors on your dump hose.  These are usually pretty effective but lack the ability to be aimed all around inside the tank.  These nozzles are designed to spray back up inside the tank past the dump valve without washing sewage off the inside of the hose,  which can happen if you just run water back through the dump hose.   Lacking a backflush adapter you can simply run clean water back into the dump hose until it flushes out the holding tank.  The most effective and convenient method uses an "EZ-Flush" system.   This is a permanently mounted nozzle in one of the walls of the holding tank that is connected to a female hose connection like the one for your city water hookup.  You just hook up the hose and turn on the faucet and let it run until the stuff draining from the dump hose is clear.   "Black water" is usually actually blue, green, orange, or brown depending on the type and concentration of chemicals -- or lack thereof!  Properly treated black water has a somewhat unpleasant odor but won't smell excessively bad, but inadequately treated waste will be horrific!

Black water tanks are vented through the roof of the RV.  Any damage to obstruction of  vent will result in unpleasant odors making their way into the interior.  Sometimes careless installation of accessories may allow a screw to penetrate the vent pipe and that too can allow odors to enter,

A cool idea.   If you suspect solid wastes are building up in your black water tank (e.g., the sensors read full or you can see a pile of stuff in the tank when you flush the toilet even after you've just dumped the tank) you might try dumping some ice cubes and water down the toilet and driving around.  Be sure to add plenty of water.  You want enough so the water and ice cubes will slosh around and loosen stubborn deposits while you drive.  The ice will help scour and loosen deposits but will then simply melt and flush out without leaving any additional solids behind.

Another suggestion for keeping the black water tank clean is to add some fabric softener to the black water tank after you've dumped and rinsed it the first time along with some clean water.  Then drive around for a while to mix the softener and slosh it all over the inside of the tank.  It is said to help keep stuff from sticking to the walls of the tank as well as mitigating odors.

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) or a damaged vent pipe.  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.  You can usually distinguish whether the odors are coming from the gray water or black water tank.  Black water tank odors are more pungent and usually come from the toilet (perhaps the shower if the shower drains into the black water tank).  Gray water odors will be more musty or smell like dirty dishwater and usually come up through a sink drain or escape through a faulty vacuum breaker inside a cabinet.  A faulty vacuum breaker won't release black water tank odors into your RV.   If your shower drains into the black water tank, make sure there is water in the P-trap to avoid odors from entering your rig.  If the shower hasn't been used in a while,  run a cup or two of water down the drain to fill the P-trap.  If you overfill the black water tank it may back up into the shower, creating a REALLY nasty, smelly mess!

A common cause of sewer odors in RVs is a plugged vent pipe.   Holding tanks are vented via pipes through the roof.  If the vent or the pipe gets plugged, odors will build up in the tank and seep into the living space.  If you experience persistent sewer odors in  your RV, remove the vent caps and inspect and flush the pipes to make sure they are clear.  Loss of a water seal in the P-traps of the sink and shower drains can allow odors to enter through the drains.  Water may be lost during ascending or descending steep slopes or negotiating sharp turns or on rough roads.  Simple adding a cup or two of water down each drain will solve this problem -- until violent movement empties them again.

Dumping of holding tanks is one of the least appealing tasks associated with owning an RV.  Many people find it revolting, but done right it doesn't have to be.  Proper dumping requires a good dump hose and a proper dump station.  Most dumping of holding tanks is done using gravity only using a 3" dump hose but there are pumping systems, called maserators, that grind solid waste and pump it out through a 1" garden hose.  This allows you to pump waste uphill and, if you don't have access to a proper dump station, you might be able to pump waste into a toilet or through a clean-out plug on your home sewer system.  Periodically check your sewer dump hose to make sure it hasn't developed loose connections or leaks.  The hose may wear through while in bouncing around in storage, so be sure to check it out BEFORE you need to use it.  Cap one end and raise the other end about chest height and fill the hose with clear water.  If there are any worn spots you should see little sprays or drips of water.  If you do, replace the hose before dumping your tanks or you'll have a nasty mess to clean up.  Sewer hoses come in different thickness or grades.  The heavier or sturdier the hose, the longer it will last and the less likely it will leak.  Lighter weight hoses are often much less expensive and will do the job (for a while), but plan on replacing them more often.  Properly designed black water systems should drain completed through the dump valves but you may need to raise the side of some RVs opposite the dump valve to ensure complete flushing.  Locate the dump valves and position the vehicle so the dump valves are in line with the dump station and so that the dump station is within reach of your dump hose.  Some people carry extra lengths of hose and connectors to tie them together in case they can't get close enough to the dump station.  Most dump stations are designed so you can get the RV very close and the most common use of extended sewer connections is for use with full hookups when the dump port isn't near the position of the dump valves when the vehicle is parked in the site.

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.  If your monitor doesn't seem to be working correctly the sensors are probably contaminated.  A thorough rinsing of the tank might help correct the problem.  You might find special chemicals for cleaning the sensors at your favorite RV supply store.

Porta-pottys and other portable toilets require about the same procedures as RV black water tanks. They will need to be properly dumped and flushed regularly and treated with appropriate chemicals to control odors and break down wastes.

Black water systems are subject to freezing when the temperature drops below 32° F.  Depending on the concentration of chemicals and biological contaminants, the freeze point might be a little lower, but protecting it at 32°or less should always be safe.   If your dump valves are in an enclosed cabinet, leaving a 100 watt incandescent light bulb burning may be enough to keep them from freezing.  Since 100 watt incandescent bulbs are being phased out, you may have to settle for a 60 or 75 watt bulb.   Or use a bulb for a heat lamp or get a reptile warming light from a pet store.  If your valves are exposed you'll need heat tape and/or antifreeze to protect them.  Adding RV antifreeze to the black water tank may prevent it from freezing solid and splitting the plumbing or the tank.   Check with your local RV shop to determine how much antifreeze you need for the size of your tanks.   A gallon should usually be enough added to an empty tank to fill and protect the valves, but you may need a lot more to protect the entire tank if you're using the RV in sub-freezing weather.  The chemicals and waste products in "black" water may lower the freezing point some, but I'd rather not risk having the tanks freeze.  Clean water freezes a 32°F; chemicals and other contaminants may lower the freeze point some.  If a tank or pipes freezes and splits you're going to have a very, very nasty mess in and/or under your RV when it warms up!  Exposed drain pipes are even more susceptible to freezing and need to be protected with heat tape or antifreeze if the RV is used in freezing weather.

One of the most important keys to keeping black water tanks functioning properly is appropriate use and regular, thorough dumping and cleaning.   Appropriate use includes using the right toilet paper, avoiding putting clog-inducing materials (diapers, sanitary napkins, paper towels) in the toilet, and using the right amount of water when flushing.   When boondocking you want to minimize your water usage, but using too little water to flush will result in solid waste buildup that will inhibit dumping and create nasty odors so you need to learn how to balance usage for best results.

Flush it!