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RV Black Tank Cleaning Guide

June 26, 2024

Your RV’s black water tank is a crucial piece of equipment that collects everything that goes down the toilet, including human waste.

Depending on the RV, it can hold anywhere from 15 to 50 gallons of waste.

However, you never want it to wait until it’s full before dumping. That can cause the tank to overflow, which can cause slow draining or backup in the shower or toilet.

Not only that but it can also cause unpleasant odors to develop. That’s why it’s so important to empty the tank at regular intervals, ideally, when it’s 2/3 full

Cleaning the black tank is also important. Not only will it keep odors and blockages at bay but it’ll also allow the tank sensors to work efficiently so that it will give you the most accurate readings.

How do you clean the black water holding tank? What products should you use? Can you clean it at the same time as the gray tank? For the answers, be sure to keep reading!

How Often Should You Clean Your RV Holding Tanks?

how often to clean rv holding tanksA good rule of thumb is to clean the black tank once a month, or once every two months, depending on your usage. For example, if you’re in the RV full-time, it’s a good idea to clean the black holding tank once every 5-10 dumps.

Keep in mind, however, that the gray water tank, which holds wastewater from the sink and shower, should be cleaned more frequently – about once every two weeks, or when you return from your trip.

Benefits of Cleaning Your RV Black Water Tank

Keeping your black tank clean comes with several benefits, which we will be going over below.

It Will Help Prevent Odors

Regular cleaning will help eliminate bacteria that release foul odors as they break down the liquid and solid waste products in the tank. That will help prevent unpleasant odors from developing.

It’ll Help Prevent Costly Repairs

An unmaintained tank can easily lead to clogs and blockages, which can result in costly repairs. For example, it can overflow and clog the toilet, or worse, it can cause a backup in the sinks and showers.

It’ll Increase the Longevity of Your RV

Cleaning the black waste tank will increase the lifespan of your RV tank system by preventing critical malfunctions.

How to Clean Your Black Water Tank – A Step-by-Step Guide

The cleaning process can be broken down into a few steps:

Step 1: Drain Your Black Water Tank

drain your black water tankYou can’t clean a holding tank that’s full of waste; that’s why you want to empty it first.

Before you begin, make sure the RV is level. Use jack stands to level the vehicle if necessary. It’s also a good idea to close the vents and windows to prevent the odors from seeping inside.

Put on a pair of rubber gloves and attach your sewage hose to the black water tank valve and sewer inlet. We recommend using a clear sewer attachment to connect the hose to the inlet as that will allow you to see the color of the water that is draining out of the tank.

Once the hose is attached on both ends, open the black water valve. The contents of the black tank will automatically begin to drain.

Wait for it to drain completely before closing the valve.

Tip: If necessary, you can raise the angle of the hose with a sewer hose support – that will allow the waste to drain more easily.

Step 2: Drain Your Gray Water Tank

Next, open the gray water tank valve. If your RV has a separate hose connection for the grey tank, make sure to unhook the hose from the black tank and reattach it to the gray tank before starting.

Wait for all of the soapy sink and shower water to drain from the tank, then close the valve.

Remember, you always want to empty the black water tank first before proceeding with the grey tank. That way, the soapy water from the grey tank will help rinse out the sewer hose.

Step 3: Flush Out the Black and Gray Tanks

flush out black and gray tanksLocate your RV’s black tank flush inlet – it should be on the exterior wall, next to your city water connections.

Connect a standard garden hose to the flush inlet and the other end to the water supply. Make sure that you’re using a designated hose for the black tank; you don’t want to use the one for your RV’s fresh water tank.

Fill the black water tank until it’s two-thirds full, then drain it by opening the black tank valve.

Do the same for the gray water tank by running the kitchen and bathroom sinks and shower at full blast.

Close all the black and gray tank valve once the tanks are empty.

Step 4: Refill the Tanks and Apply a Treatment

Once the black and gray tanks have been drained and flushed, you’re ready to treat them with a cleaning solution.

While some people also treat the gray tank, it’s not absolutely necessary as it only collects water from the shower and sinks.

In terms of the treatment itself, there are many options. While you can use homemade methods, store-bought options may be a better choice as they’re specifically formulated to clean and sanitize the holding tanks.

Take ACTIVE Holding Tank Digester Treatment, for example, it’s formulated with non-pathogenic bacteria and enzymes to liquefy and digest solid waste inside the tank, which will help neutralize odors and maintain sensor performance.

Simply add the black water treatment to the RV toilet, according to the instructions on the product packaging, and flush. The treatment will end up in the black tank, where it will automatically work its magic.

For the best results, let it sit in the tank for a bit before emptying and repeating the cleaning process.

Depending on toilet usage, you may need to repeat the treatment 1-2 times a week.

Backwashing a Black Water Tank

Some RVs come with a back flush valve, which allows you to wash the inside of the black water tank with pressurized water.

Connect the Hose to the Back Flush Valve

flushing black water tankConnect your hose to the built-in back flush valve – the other end should be attached to the water supply.

Open the black water valve and the pressure washer relief valve (check your RV’s manual for specific instructions) – that will fill the inside of the tank with pressurized water, which will help remove stuck-on debris.

Cleaning the Black Water Tank With an RV Tank Wand

An RV tank wand is designed to flush out and dislodge stubborn deposits after the tank has been emptied.

The wand comes with a power nozzle that sprays a jet of water at high pressure. There is also a knob that you can use to control the water’s flow.

How to Use an RV Tank Wand

Open the black water valve and attach the non-potable water hose to the handheld wand.

Carefully feed the wand and hose through the window and lower the wand through the toilet so that it enters the waste tank. Remember to keep the toilet bowl valve open by pressing on the flush pedal.

To release water from the wand, open the shut-off valve.

Move the wand around through the toilet to clean the floor and walls of the tank with pressurized water. Once the black tank is clear (keep an eye on the clear sewer attachment), remove the wand from the toilet.

Removing Solid Debris with a Macerator Pump

A macerator pump uses a fast-rotating blade to grind solid and fluid waste into a fine slurry that can easily be expelled through the sewer line.

It’s a great option if your black tank valve or sewage hose is clogged by debris or residue.

How to Use a Macerator Pump

Start by closing the black water valve. Disconnect the sewage hose from the black water tank and attach one end to the macerator. The other end should be attached to the tank valve.

Turn on the macerator pump (some use electricity while others use a separate hose) and it will begin to grind up any waste.

Continue to run the pump until the flow stops.

Other Important Tips

Here are a few things to keep in mind when it comes to maintaining your waste-holding tank.

Only Use RV Safe Toilet Paper

rv toilet paperThere are a few things that can wreak havoc on your black water tank if it goes down the toilet. For example, you should never use household toilet paper.

Not only are they much thicker, which makes them prone to clogs, but many are also colored and perfumed and the last thing that you want is to introduce chemicals into your RV’s sewage system.

The same goes for paper towels, feminine hygiene products, baby wipes, and facial tissues. These items should never be put into the toilet

Clean the Sewer Caps Regularly

Make a habit of cleaning the sewer caps once in a while – both for the black and gray tanks. We recommend wiping the caps and adding a thin layer of grease around the ‘O’ ring seals to prevent leakage.

For example, you can use Plumbers Heat-Pruf, which is heat-proof, or Vaseline.

Always Use a Designated Dump Station

Make sure you’re at a designated dumping site when emptying your black water tank. You should never dump it anywhere else as the waste products can easily enter the ecosystem and harm wildlife.

The same goes for the gray tank. While it’s technically legal to dump it on the ground since the water was also used for washing, it’s best to do so at a designated sewage facility or dump site as the soapy water can have negative impacts on the environment.

This is true even if you use biodegradable dish detergent and soap. For example, it can affect the pH of the soil, which in return, will affect the plants’ ability to thrive.

Not only that but the gray water can also enter waterways such as rivers, streams, or lakes, where it can affect animals and humans by causing algae blooms.

Wear Personal Protective Equipment

Always wear personal protective equipment when cleaning or emptying your holding tanks. The last thing that you want is to get wastewater on yourself.

This means wearing rubber gloves (either disposable or reusable) and or a face mask before starting.

Maintaining a Clean Black Tank In RV – FAQs

How often should you flush the black water tank?

maintaining a clean black tank in rvThe frequency will depend on several factors such as the size of your tank and the number of people in the RV. For example, you may need to flush the tank more often if you’re traveling with a larger group.

Having said that, many swear by the 2/3s rule, where you flush and clean the black water tank when it’s 2/3 full. Avoid waiting until it’s completely full as that can lead to overflow and other issues, which can result in costly repairs.

Should you clean the gray water tanks before the black tank?

No, you should always clean the black water tank before the gray tank. That’ll allow you to rinse the sewer relief hose with the soapy water from the gray tank.

What should you treat the black water holding tank with?

active holding tank treatmentWe recommend using ACTIVE RV & Camper Holding Tank Digester. It’s formulated with bacteria and enzymes and will keep your RV smelling fresh by neutralizing odors and maintaining toilet functionality. Not only that but it will also help maintain sensor performance.

Begin by emptying the black tank and flushing it with two gallons of water. Pour enough water into the toilet so that it’s half-full and add the treatment liquid.

Flush the toilet and hold the pedal for 10 to 15 seconds to fully flush the treatment.

If necessary, you can also use it to treat gray tanks. Simply pour two oz of the treatment liquid down the shower drain or sink and run a gallon of water from the faucet or shower afterward.

Can you clean RV holding tanks with bleach?

Yes, you can clean and sanitize the black water tank with bleach. Ideally, you want to do it when the RV is fully hooked up to a sewer and water connection.

Don’t add bleach directly to the tank, though. You want to create a solution by mixing one-quarter cup of bleach with a gallon of water. The exact amount will depend on the size of your holding tank.

Once you’ve created the bleach mixture, add it to the tank and let it sit for 8-12 hours. The bleach will kill off any pathogens that are inside the waste tank.

Afterward, you can empty the tank at a designated dumping station.

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Marcus Washington

Marcus Washington is a well-rounded expert in RVs and campers. With a wealth of experience, Marcus shares his expertise through his valuable guides, helping enthusiasts and newcomers alike navigate the world of mobile living. His advice covers everything from maintenance to maximizing space, ensuring every road trip is smooth and enjoyable. You can trust Marcus to guide you in your RV and camper adventures.

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