RV Holding Tanks, Tips & Tricks
to Waste Water Storage

RV holding tanks and waste water management aren't topics that excite too many RVers. The truth is holding tanks are a part of RV life - and without them we'd all be chained to a campground. Without holding tanks, RVing wouldn't be so fun, or so free - and RV boondocking would be just a dream.

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This is your Glorious Guide to RV Waste Tanks. Topics I'll cover include:

  • RV Boondocking Tank Tactics
  • Portable Holding Tanks
  • Holding Tank Repair
  • Holding Tank Chemicals
  • RV Macerator Pumps
  • Holding Tank Sensors

RV Boondocking Tank Tactics

RV Holding Tanks RV holding tank

With a little RV boondocking experience under your belt, you'll soon discover how long you can camp before your RV holding tanks are topped off. If your tanks are filling up sooner than you'd like, keep reading... 

There are two important factors to look at when boondocking:

  • Holding tank size
  • Amount of waste water entering tanks

Holding Tank Size

When you stay in full-hookup campgrounds, the size of your holding tanks is irrelevant and you need not be concerned. However, when RV boondocking it becomes crucial - you must store your waste water until a dump station is to be found.

The size of your RV holding tanks is usually dependent on several factors such as:

  • The Manufacturer
  • Available Space
  • Floorplan Design
  • Size of the Fresh Water Tank

The larger the waste tanks are, the longer you can camp before a run to the dump station is required. If you'll be doing some RV boondocking, go with an RV that has large holding tanks. For a camper van, a 20 gallon grey water holding tank would be considered large...but certainly not in a Class A motorhome or 5th wheel travel trailer. 70 gallon tanks and larger can be found on these rigs.

Waste Water Reduction

When RV boondocking, you'll be conserving water and this will reduce the amount of waste water going down your drains and into your holding tanks. Here are several tips & tricks which will enable you to do more camping, and less dumping.

  • Never let water go unused. Don't let the faucet run the entire time while washing hands or brushing teeth. When waiting for water to get hot, use a container to capture the cold water for other uses.
  • Low flow showerhead and on/off switch installed to conserve waterLow flow handheld shower and 100% shower shut off valve installed
  • Take "Navy Showers" - Turn the shower on to get wet, turn off while you soap up, then turn on again to rinse. A shower head shut off valve can be installed at the showerhead to make this easier. Make sure it's a 100% shut off valve, as most do not completely shut off the water but allow for a trickle while in the off position. You can also use a low flow handheld shower or low flow showerhead to conserve even more H2O. I've done both as shown in the picture here.
  • Mark each hot & cold knob on your shower so you won't have to play around to get the right temperature next time.
  • Shower outside with a solar camp shower filled from your RV, or from a lake or stream to conserve your fresh water supply.
  • It doesn't take much water to flush the toilet. Use a high quality spray bottle (the type used for gardening has a more forceful spray) for a final rinse of the toilet bowl.
  • Conserving water while washing dishesConserving water while washing dishes
  • Use a hand sanitizer instead of water to wash hands.
  • Dishwashing - Use paper towels to wipe dishes off before washing. Then, heat up a little water in a pan on the stovetop, and wash the dishes out of this pan. Rinse in another pan or bowl of cold water. Pour water outside, on a plant, when done.
  • Use paper plates and bowls to cut down on dishwashing.
  • Keep a jug of water outside for washing your hands & face.
  • Pour excess water used in cooking outside on a plant.
  • Put used toilet paper in a paper bag that can be burned later. This will reduce the amount of waste going into your black water tank.

Portable Holding Tanks

Portable Holding Tank - SmartTote by ThetfordPortable holding tank by Thetford

Do you enjoy RV boondocking, but hate breaking camp to make a run to the dump station? Consider a portable holding tank, or "blue boy" as they're often called because many are made of blue colored plastic. The Original Tote-Along by Barker Manufacturing is a very popular choice. You can transfer your black and grey water from your RV's holding tanks to the portable holding tank, which can be hauled to the dump station. This way you avoid having to break camp.

Portable holding tanks range in capacity from 5 to 42 gallons. Some RVers mount them on their truck or tow vehicle and fill them with an RV macerator pump, which can pump waste uphill. Many portable holding tanks have wheels and a tow handle that fits over a ball hitch so the tank can be towed with a car. Smaller versions can be wheeled by hand and picked up and placed in your vehicle.

Use caution when towing a portable holding tank, especially if traveling on any surface which isn't paved. Losing a wheel or hitting a rock could make for a memorable experience, in the olfactory sense!

RV Holding Tank Repair

Almost all RV holding tanks are made of thermoplastic, which is highly durable & resistant to freeze damage. ABS and polyethylene are the most common types of thermoplastics used.

Tough as these tanks are, there is a limit to how much abuse they can take. Holding tanks are typically located underneath the RV where hazards include rocks, curbs, and potholes. Bottoming out when entering or exiting steep driveways is another threat. Road hazards can damage your RV holding tanks, and in worst cases, take them out completely.

Thankfully most cracks and leaks can be repaired. However, if the RV waste tank has several cracks, or a large hole, it may be time for a replacement. In most cases, RV holding tank repair will require that the tank be removed. All RV holding tanks, including the fresh water tank, must be removable by design, to allow for repairs or replacement.

RV holding tank repair can be performed with a plastic repair kit if the tank is made of ABS plastic. Plastic welding will repair a tank made of polyethylene, ABS or any thermoplastic. Welding plastic requires specialized equipment, so it's best to have an RV service shop do the repairs.

Holding Tank Chemicals

The sights, the sounds, and oh yes, the smells of real RV camping. If some of those smells weren't in your travel plans, then read on...

In the past, formaldehyde-based chemicals were used to mask RV holding tank odors. Now that the dangers of formaldehyde poisoning are known, there are much safer ways to deal with holding tank odors.

Aftermarket Holding Tank Vents

Xtreme Vent by Coil n' Wrap - RV Holding Tank VentXtreme Vent by Coil n' Wrap

Want to eliminate odors without the use of harmful holding tank chemicals? The answer is an aftermarket holding tank vent like the RV Cyclone Sewer Plumbing Vent by Camco. These vents take advantage of the Venturi Effect to draw air (and odors) out of your holding tank through the vent pipe.

The vents work with even the slightest breeze and are easy to install. By providing more oxygen to your RV holding tanks, these vents also speed up the biodegradation process, further removing odors.

Holding Tank Treatments

RV Holding Tank Treatment by Thetford

If you must use an RV holding tank treatment, don't use chemicals. Use a product that is all natural, non-toxic and based on organic compounds such as Unique RV DIGEST-IT Holding Tank Treatment.

Before choosing any holding tank treatment, always read the label first.

Avoid any holding tank chemicals or treatments that contain the following hazardous substances:

Active ingredientHuman & Environmental Danger
(chemical name: bromo-nitropropane-diol)
bacterial pesticide
(chemical name: 1-(3-chlorallyl)-3,4,7-triaza-1-azoniaadamantane chloride)
bacterial pesticide (EPA states “Do not discharge effluent containing this product to sewer systems without previously notifying the local sewage treatment plant authority.”)
(also known as Formalin; degradate of bronopol)
kills or retards bacterial growth, recognized by EPA as probable carcinogen (1); moderately toxic to humans (2)
(also known as embalming fluid)
Retards bacterial growth and covers sewage odor, eye and inhalation irritant
(polymerized formaldehyde)
very toxic to humans (3) (see formaldehyde)
(common ingredient in mothballs, urinal cakes, and
toilet bowl fresheners)
known carcinogen (1) and drinking water contaminant; moderately toxic to humans (2)

(1) a carcinogen causes cancer
(2) lethal dose for 150 lb person is between 1 ounce to 1 pint
(3) lethal dose for 150 lb person is between 1 teaspoon to 1 ounce
This fact sheet was adapted from Alert for RV, Boat and Mobile Home Owners and Park Operators About Safe Wastewater Disposal, EPA Publication 909-F-99-002, July 1999.

Grey Water Holding Tank Odors

Do you leave the grey water dump valve open when connected to a campsite?

Consider this: Leaving the dump valve open will cause the tank to dry out. Grey waste matter becomes stuck to the walls of the tank and once nature works its magic, peeyou! You've got a big smelly mess on your hands.

But that's not all...since you're connected to the campground's sewer system, you'll be venting its odors as well! Odors from the campground's sewer system move up your sewer hose, into your grey water holding tank, and out your holding tank vent. If you prefer not to turn your campsite into a municipal sewage vent, it's best to leave the grey water dump valve closed. Only dump the contents once the tank is over 3/4 full. This is also recommended for the black water holding tank as well.


RV Plumbing P-Trap

If you smell grey water holding tank odors inside your RV, check the P-traps. P-traps are located under every drain, except for the toilet. You will see a U-shaped section of pipe.

Water is held in the P-trap and this water blocks odors from rising up through your drain pipes. However, if this water is absent due to the sloshing action while driving, or the suction created when emptying the grey water tank, odors can freely pass up the drain pipe. Pour a little water down each drain and that should block the odor.

Extreme Black Water Holding Tank Odors

Do you require a gas mask anytime you're within 100 feet of the RV? Your black water holding tank could probably use a good flush & freshening up.

Dump the black water tank then fill it to the brim with fresh water. Next, add a couple cups of baking soda. Let the tank sit for a couple days, then dump the tank. This should clean things out and add some much needed oxygen to the system, giving the black water tank a fresh start.

RV Macerator Pumps

Worried about overfilling your portable holding tank? Or perhaps gravity isn't always on your side when dumping the RV holding tanks? Poorly designed dump stations make it difficult to empty the tanks completely.

RV Macerator Pump - RV Sani-Con by ThetfordRV Macerator Pump by Thetford

An RV macerator pump such as the Flojet Waste Water Pump solves these problems. With a macerator pump, you control the flow, and you can even pump waste uphill. You control the flow by switching the pump on and off. RV macerator pumps also grind up the waste. They allow you to use a garden hose for dumping, instead of the standard 3 inch sewer hose.

An RV macerator pump also makes quick work of emptying the holding tanks, speeding up this rather unpleasant chore. These pumps run off 12 volt power and twist onto the end of your sewer pipe. Since you can pump waste uphill, they're perfect for transferring waste to a portable holding tank mounted on a truck or tow vehicle.

Holding Tank Sensors & Flushing

RV Holding Tank SensorsHolding tank sensors

Holding tank sensors can often give false readings. Of course, if your RV isn't level the reading can be off. Most likely though, you'll have waste matter stuck to the sensor, giving the holding tank monitor a higher reading.

Cleaning the RV holding tank should solve the problem. You can flush the tank clean with a product like the Valterra RV Hydroflush which fits between your sewer pipe and the sewer hose. I've had good results with this product. For a more thorough cleaning try a "toilet wand" like the Valterra Master Blaster Tank Wand which can be stuck down the toilet to give the holding tank a better rinsing.

And lastly, there's the old bag of ice cubes down the toilet trick: Once the black water holding tank is empty, dump a bag of ice cubes down the toilet. Then take the RV for a drive and as the ice is bounced around it scrubs the sides of the tank clean.


I hope by now you realize there's no reason to be "down in the dumps" when it comes to RV holding tanks. Typically, problems are few and a little maintenance should keep your holding tanks functioning properly for years to come.


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