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Is It Safe to Use Dawn Dish Soap in RV Black Tanks?

Is It Safe to Use Dawn Dish Soap in RV Black Tanks?

Besides keeping your dishes clean, Dawn dish soap has many potential uses. Many RVers quickly discover that an RV black tank can become pretty stinky, especially if you don’t keep it clean. So while Dawn dish soap can be an effective cleaning agent, is it safe in RV black tanks? Will it keep your black tanks clean and smelling fresh? Let’s look and see!

Do You Need to Put Cleaner in Your RV Black Tank?

Your black tanks store everything you flush down your toilet. While you may empty them at the end of every trip, that doesn’t mean they’re squeaky clean. Pieces of toilet paper and waste will stick to the inside walls of your RV’s black tank. While you won’t be needing your black tank for any other reason, it is helpful to occasionally clean your black tank to prevent build-up, tank level sensor failure, and a constant odor you can’t escape.

Putting cleaners into your RV black tank can help keep them clean and prevent odors from infiltrating your RV. Many RV toilet chemicals work to neutralize odors and clean the tank while it’s in use, but some of these contain harmful chemicals like formaldehyde that some people prefer to avoid.

Is It Safe to Use Dawn Dish Soap in Your RV Black Tank?

Dawn dish soap is a safe and 90% biodegradable dish soap that will not cause any issues for your RV black tank. It is a strong and highly effective cleaning agent that will help your tanks smell better.  

Dawn dish soap is safe for RV black tanks and the environment. You won’t have to worry about tossing harmful chemicals into the dump station that could cause any issues for future users or those who manage the dump station.

Pro Tip: Use our RV Black Water Tank Survival Guide to make your RV life easier.

Close up of RV black tank
Black tanks can get gross quickly! You’ll want to regularly clean yours while RVing.

How To Use Dawn Dish Soap in Your RV Black Tank

One of the best ways to use Dawn dish soap in your RV black tank is to fill the tank halfway with soapy water. Take your RV for a drive around the block or to your next campsite, and dump your tanks. This will help slosh it around and break up some of the odor-causing bacteria and grime stuck to the inside walls of your black tank.

Since you’re not going to be scrubbing the inside of the tank out, this method will likely not get everything out. However, it will create a coating of cleaner that can continue to work going forward.

How Much Dawn Dish Soap Do I Need for RV Black Tanks?

You want to use a generous amount of soap, but don’t go overboard. It would be best if you didn’t use more than a cup for the entire tank. A cup should be plenty to do the job, and any more might run the risk of bing too soapy.

Pros & Cons of Using Dawn in Your Black Tank

You might consider using Dawn dish soap in your black tank for many reasons. First, Dawn dish soap is cheap and readily available. You can find it in stock at almost any grocery store or big-box retailer selling cleaning supplies. Secondly, Dawn dish soap is mostly biodegradable and safe for your RV. It won’t corrode your tank or any of the sensitive components in your plumbing system.

Will Dawn Dish Soap Help With Smell?

Dawn dish soap is effective at eliminating odors. However, it’s not like you’re going to be scrubbing your tank clean with a brush. Dawn soap will not get everything out of your tank on its own or eliminate all odors, but it will likely help improve them.

You can find Dawn dish soap in various scents too. So not only will it rinse away the odor-causing bacteria, but it can leave behind a cleaner and fresher scent. However, you will still want to use odor neutralizers when the you start filling the wastewater back up.

Will Dawn Create Too Many Bubbles?

Dawn dish soap will create some bubbles in your RV’s black tank. Unless you add an obscene amount of soap, it will likely not make too many bubbles. Bubbles may be helpful with knocking off loose pieces of toilet paper and other substances on the inside of your tank.

While you should be generous with how much Dawn dish soap you dump into your tank, you don’t want to go overboard. If you do, you could end up with soap suds coming out of the vent for your RV’s black tank. Typically, a cup of Dawn dish soap will be enough for most large RV black tanks.

Is Dawn Detergent Biodegradable?

Dawn dish soap is 90% biodegradable. However, 10% of dish soap is from synthetic materials that do not break down. Even though it’s a small percentage, it can impact the environment, especially if you don’t dispose of it properly. Excessive amounts of Dawn dish soap can harm plants and other vegetation in an area. If you use it when cleaning your RV’s black tank, ensure it finds its way into the dump station to avoid any potential issues. Also, remember to never dump your black tank wastewater on the ground.

Woman pouring Dawn dish soap on sponge
Dawn dish soap is almost entirely biodegradable which makes it a safe option for your RV black tank.

Is There Anything Special About Dawn Dish Soap?

Dawn dish soap is one of the best-selling brands on the market. It’s been around since 1973 and is a product of Procter & Gamble. While people most commonly use it for washing dishes, you can also use it to unclog toilets, treat laundry, and protect your plants. There’s almost nothing Dawn dish soap can’t do!

Dawn dish soap separates itself from the rest of the pack with its incredible ability to cut through grease and other gunk. In 2010, Dawn spokeswoman Susan Baba credited the balancing of surfactants for Dawn’s extreme effectiveness.

If you want to know what makes Dawn dish soap unique, you’re out of luck. The ingredients (water, sodium lauryl sulfate, sodium laureth sulfate, lauramine oxide, sodium chloride, phenoxyethanol, PEI-14 PEG-10/PPG-7 copolymer, methylisothiazolinone, fragrance, blue 1, yellow 5, red 33) are public, but the specific formula is top secret.

Before Adding Any Cleaners to Your Black Tank

Whether you use Dawn dish soap or another cleaner, you must empty your tanks. Once empty, you’ll want to perform a black tank flush a time or two with nothing but fresh water. Let the tank fill up 75% of the way and then empty it at least twice.

Once you’ve thoroughly flushed your system, add several gallons of water to your black tank and dump the soap into the toilet. Having plenty of water in your black tank will activate the Dawn dish soap and help get it to start cleaning the inside of your tank.

It’s even better if you can drive your RV around and let the soapy water slosh around the inside of your tank. It will clean off the gunk sticking to the inside of your tank and help your tank sensors to stay as accurate as possible.

Pro Tip: Dumping your black tank can get messy. Find out how to Simplify Black Tank Dumping with an RV Macerator Pump.

dumping rv black tank
Fill up your black tank with some soapy water and drive around a bit so it will clean all sides of the tank.

How Often Should You Clean Your RV Black Tank?

How often you should clean your black tank entirely depends on how you’re using your RV. If you’re a weekend warrior and there are weeks between trips, you should clean your RV’s black tank at the end of every season. However, if you’re traveling in your RV full-time, you’ll likely want to clean it or flush it about once per month. Should you notice that you frequently experience odors in your RV coming from your black tank, you’ll want to increase the frequency of cleaning.

Dish soap in bottle on window ledge
Use about a cup of Dawn dish soap to clean your tank.

Alternative Chemicals for Cleaning Your Black Tank

There are some products specifically for cleaning RV black tanks. Various companies manufacture powders and pods. Some popular options are Camco’s TST MAX RV Toilet Treatment pods and Happy Camper RV Holding Treatment powder. These excellent products are easy to use and will do the job.

One of the great things about these products is that they’re solid and practical but not so strong that they’ll damage the plastic components in your plumbing system. Using harsh chemicals like bleach can be extremely dangerous for your system. Bleach will eat away your black tank and the rubber seals and gaskets throughout the system.

In addition, mixing bleach and urine can create chlorine gas. This gas can be highly irritating and pungent. Common side effects of this gas are watery eyes, a runny nose, and coughing. Take your safety seriously before you start dumping chemicals into your black tank.

RV Black Tank Cleaning, Maintenance, Tips & Tricks - A Complete Guide to RV Waste Tanks!

Dawn Dish Soap in RV Black Tanks: It’ll Work

If you want to clean your RV’s black tank, Dawn dish soap is an cheap way to do it. Dumping a cup of Dawn into your black tank only takes a few minutes, but the results are worth it. The key to avoiding a smelly RV is regularly cleaning your RV’s black tank. You don’t want gunk sitting in your tank for extended periods, which will cause them to grow and the odors to worsen. So grab the Dawn and take action today!

How often do you clean your black tanks? Tell us in the comments!

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About Mortons on the Move

Tom & Caitlin Morton of Mortons on the Move gave up the stationary life for one where they are constantly on the move. They are full-time travelers, television hosts, and digital media producers.
They left their jobs, sold their house and possessions, and hit the road in September 2015 in their full-time “home on wheels”. Since then they have traveled the US, Canada, and even internationally by RV.
Now, they are Discovery Channel & PBS TV Co-stars of The RVers, producers of “Go North” on Amazon Prime, co-founders and instructors of RV Masterclass, and contributing authors for and an Arizona travel guide.

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Mike Daw

Thursday 26th of January 2023

We've found that dishwasher pucks or little bags the most effective. They're designed to not have to much suds but also to cleane and remove greasy and hard to remove pieces.


Thursday 26th of January 2023

When we got our latest 5th wheel four years ago, I did a lot of research on waste tank treatments and adopted the following procedure - After flushing the tanks (black and gray) I pretreat them with 1 cup of Borax and one cup of Dawn dish soap and wash down with 2 gallons of water every time we dump. We camp at least 6 months out of the year and this procedure has kept our tanks clean and easy to dump (everything is liquified), and we have no odors. There are a lot of things that grow in the gray tank as well as grease. One thing to keep in mind that I have learned as a plumber is that poop has a lot of grease in it and this procedure breaks it down. It also helps keep your dump hoses clean and better smelling.

Gil Strachan

Thursday 26th of January 2023

A cup of any dish soap and a cup of Borax, plus a couple of full bowl flushes to start the tank... works like a charm!

Meg M 94

Tuesday 3rd of January 2023

I do not have a Black Tank, due to having a Composting Toilet, but upon RV Geeks suggestion in my gray tank, I add liquid dishwasher soap. Chose 7th generation since it is more natural, but may alt with Dawn. We needed for the Gray to keep it smelling nice and pipes cooking fat free. We will go several trips with out dumping so I wanted to prevent odor. It has been successful for 2 football and 1 baseball tailgating season.


Monday 2nd of January 2023

We can boondock for about 4 days before we "dump" We have a Tear Drop We flush the tank 2-3 time then close it up and use Digest-It. I might consider using Dawn on our last trip before heading home We've been traveling for 9 months with no problems (knock on wood)

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