RV Holding Tanks: The Ultimate Guide
By Kelly Beasley
An RV is essentially a house on wheels.
No matter whether it's a travel trailer or a motorhome, it probably has every home need from sinks with running water to a furnace, to electricity, powered by batteries or a generator.
If one has a kitchen sink, a shower, and/or a conventional toilet, it also comes with RV holding tanks to store the water and waste you put down the drain.
All the comfort of home!
Why? Because there are times when campers don't have utilities in a campground.
Some people want to camp on public lands or in areas or campgrounds that do not offer utility services such as water, power, and a sewer hole for dumping.
Therefore, almost all campers sold from a manufacturer have at least three RV holding tanks. A freshwater tank, a black water tank, and a gray water tank.
They store the water you will need when dry camping and provide a way to keep the used/dirty water before you dump it at dump stations.
Thankfully, our society prohibits dumping sewage or otherwise dirty water just anywhere, especially on our precious and fragile public lands.
Let's look a little closer at these camper holding tanks and what they do.
Fresh RV Waste Holding Tank
The fresh water tank is for dry camping (camping when not connected to utilities).
You won't be connected to a water supply, so you must bring your fresh water supply with you when you go camping.
There is no standard size of camper water tanks. Instead, your water tank capacity could range anywhere from 10 gallons to 100+ gallons.
That said, your fresh water tank is usually the largest of all of your holding tanks for RVs.
To fill, use a 'potable water' hose (usually colored white for easy identification) to fill your water tank at any potable water spigot.
You can find these at gas stations, dump stations, campgrounds, and other similar places.
Is It Ok To Travel With My Water Tank Full?
Yes, it is OK to travel with your fresh water tank full. RVs are designed to carry the weight of a full water tank while on the road.
Otherwise, what would be the point of having one? Many destinations don't provide water, so you MUST bring your own.
That said, be sure you KNOW the actual weight of your RV when it's full. Do not go past the allotted weight the manufacturer says it can handle.
If you are very close to it, you could be over when you fill your water tank. It's best not to be close at all for maximum driving or towing performance.
Grey Water Waste Tank
Next, your RV likely has a separate grey water tank.
After fresh water is used for the sink or shower, it drains down into your grey camper waste holding tank where it's held until you dump it. This camper waste tank holds everything but sewage.
That said, some very small RVs don't have a grey dump waste tank. They only have an RV sewage tank.
In this case, the water from sinks and showers then goes into the black tank.
Your grey water tank captures sink and shower water. Meaning it's nasty and stinky.
Pro Tip: Be sure to let as little food debris go down your sink as possible and into your RV waste holding tanks.
Black Water RV Holding Tank
The black water tank is the nastiest and the scariest of the three types of RV holding tanks. It can induce the fear of God into even the biggest muscle truck guy around.
NO RV owner in their right mind wants to have a spill from their black water tank at the dump station.
I had a little spill here!
Why? Because your black water tank is your RV sewer tank! YOU MAKE SEWAGE, and it goes down the facilities and into the trailer septic tank.
It should stay ONLY in the tank or go through your camper waste hose.
It's downright disgusting, but it's also a necessary evil. (Even if you have a composting latrine, you still have to dump. You have your grey RV wastewater tank to dump at the dump station.)
How Does A Camper Septic System Work?
A camper septic system works by simply acting as a holding tank for your sewage. It's not a SEPTIC TANK that works like at a house.
With an RV septic system there are no leach fields, no breaking down needed (not really), none of that. It holds your sewage until you dump it. That's it!
You go in the toilet, then flush. The water and your contributions flow down a tube and into your tank, whatever size it may be.
Water you use in the shower or sinks goes into a separate holding tank for RV use.
All the waste water stays in the trailer holding tank until you open the corresponding RV waste valve to dump it. This is what RV septic systems do.
How Big Are RV Septic Tanks?
RV septic tanks will come in a multitude of sizes. A typical RV holding tank size will range from 10 gallons to 100+ gallons. Generally, the bigger the RV, the bigger the septic system for RV will be.
Travel trailer holding tanks will generally be smaller than motorhome holding tanks because trailers are usually smaller than motorhomes. Also, motorhomes are typically equipped to carry heavier weights. (Full holding tanks for RV use are heavy!)
How To Dump Your RV Holding Tanks
Dumping your RV holding tanks is a simple process, though scary the first few times. Find a dump station. Park so your holding tanks outlet is near the sewer hole.
Connect your sewer hose to your RV and to the sewer hole. Open your camper sewer tank black valve first.
Once done, close the black water tank valve. Now, open your gray water valve.
The valves are usually labeled black or gray so you don't make a mistake. Or they are color coded as these are.
After the camper waste tanks are drained, remove the RV end of the hose and rinse it out with the water supply.
After letting most of the water drip out, remove the end from the sewer hole and put your sewer hose away.
MAKE SURE you closed off both valves, and you're done with the dump station!
How Often Should An RV Septic Tank Be Emptied?
How often an RV septic tank should be emptied has everything to do with tank capacity and how many people are using them, as well as how conservative you are with water usage.
A huge determining factor as to how long until you need to dump your camper sewage holding tank is how often, and how long, you shower. The shower is by far the biggest single contributor to filling up your camper waste water tank.
I, Kelly, can go about 3.5 weeks if I don't ALWAYS pee in my black tank and if I sometimes throw non-contaminated water outside instead of allowing it to go down into my grey tank.
Some people must dump their RV wastewater holding tanks once a week or more frequently. It would be best for you to learn your habits and your RV in order to answer this question correctly.
How Do I Clean My RV Holding Tank?
You clean your RV holding tank based upon which RV dump tank you are wishing to make sure is cleansed. The black RV sewage holding tank is the grossest to clean, but the fresh water tank is the most critical (since you often drink the water from this tank).
There's not much maintenance needed for your RV sewer tanks. Probably the fresh water tank needs the most. We'll come back to fresh water tanks below.
Meanwhile, the black and gray water RV holding tanks can sometimes have issues.
Let's start with the black tank part of the RV septic system.
Performing an RV black tank flush is a great way to limit the number of issues you'll have. Read on to learn more about what to do with this waste holding tank.
Black Tank Maintenance
The most significant issue with your septic tank for RV is clogging.
This is NOT what you want to happen. Your tanks can clog in one of three ways:
- Too much RV toilet paper and not enough water.
- Using non-septic friendly toilet paper.
- Unintentionally building a "poop pyramid" in your RV poop tank.
All of these RV waste tank issues are largely avoidable.
We all have to poo! Just avoid the poop pyramid in your black tank!
How To Avoid Black Tank Clogs
Secret #1: First and foremost, we recommend NOT putting your TP down the toilet. You will never have an RV septic tank clog if you do this.
Secret #2: Not a fan of that idea? Then NEVER use non-septic-safe toilet paper. OR shred what you have before you use it. Just splitting up a line of TP into three smaller ones will help.
Secret #3: Last, NEVER keep your black tank waste valve open while hooked up to a sewer at your campsite. If you do, you'll allow the liquids to drain out immediately. This leaves the solids behind, and they will collect where they land. This is what is called a 'poop pyramid'.
Poop pyramids eventually block the drainage of your camper septic tank.
What Can I Put In My RV Septic Tank?
You can put three things into your RV septic tank (black water from the toilet): Poo, pee, and septic-safe toilet paper.
Putting anything else into your toilet is ill-advised, such as tampons, baby wipes, diapers, etc.
The gray RV waste water tanks will hold what you put down the shower or sinks. It is advisable to not allow food waste to enter your RV waste water holding tanks and to use environmentally friendly cleansers (soaps, shampoo, etc.). This minimizes the smell from your RV sewer holding tanks (gray water specifically).
Grey Tank Maintenance
Your grey camper dump tank shouldn't need much maintenance at all.
The worst that can happen is it springs a leak or drops out from underneath your RV. However, this is rare. (It HAS happened before!) Hopefully, the worst that happens to your tanks is a foul odor.
Keep in mind that these tanks and the pipes leading to them work just like your pipes at home. Your RV sinks have 'P' traps that hold water in them, so the grey tank smells cannot get inside your RV.
Therefore, if you are experiencing odors, check your 'P' traps first. There might be a build-up of gunk in there needing removal.
The other thing that might be wrong is your vent could be stopped up.
In the 5.5 years full-time RV'd, I've never had to do anything to my gray tank except clean out the 'P' traps.
Learn more about RV grey water tank cleaning.
Fresh Water Tank Maintenance
This tank stays pretty clean for the most part.
Especially if you use a filter every time you fill. There are a few things you can do to clean and sterilize this camper tank.
Can I Put Bleach In My Holding Tank?
Yes, you can put bleach in your fresh water RV holding tank. In fact, this is the recommended way of cleaning (sterilizing) this holding tank. BUT, you must flush it all out before using any of the water!
The general rule is to put 1/4 cup of bleach for every 15 gallons of water you put in to sterilize.
You will never be able to scrub out the inside of your tank. However, there are treatments on the market designed to sterilize the fresh tank and pipes leading from the water camper holding tank.
It's best to use a water hose you only use to fill fresh potable water.
If you use the hose you rinse out your sewer hose with, well, you can imagine that it can contaminate your fresh water. This is not recommended.
How Do I Check The Water Level In My RV Tank?
You can easily check the water level in your fresh water RV tank by using the tank monitor panel. Your RV likely came with a monitoring panel that show you the level of all of your RV holding tanks.
Push a button, and it will tell you approximately how much water you have. Depending on the monitor panel, the measurements will either be in thirds (empty, 1/3, 2/3, full) or quarters (empty, 1/4, 1/2, 3/4, full).
If you are fortunate enough to have a more accurate system, measurements will be in percentage of tank capacity.
There will also be buttons to measure the levels of the camper waste water tanks. Keep in mind that the gray and black sewage tanks are notorious for reading inaccurately due to buildup on the RV tank sensors.
When it comes to holding tanks for campers, typically only the fresh water level reading will be accurate after a certain amount of use. Unless you have the type of system that reads in percentages, as this uses a different sensor technology that doesn't get clogged like the cheaper (and more prevalent) sensors.
A typical tank monitor panel.
How Do You Deodorize An RV Holding Tank?
To deodorize an RV holding tank, you need an RV holding tank treatment. Yes, your black RV tank might emit camper toilet smells. This is less than ideal.
Most often, this happens when your rig is in scorching environments. (The only time I needed a black tank treatment was when I was in Florida in the summer.) Heat tends to make a travel trailer waste tank a bit on the pungent side.
As an RV owner, if this happens to you, get yourself one of a few products. They are treatments for RV tanks.
We like Happy Camper RV treatment or Tank Techs RX for your RV tanks.
These products have enzymes that break down solid waste and eliminate odors.
Specifically, Tank Techs RX can keep everything clear so the sensors on your camper waste tanks don't eventually get covered by Struvites.
Struvites are naturally occurring in septic systems and create hard deposits that cause your sensors not to read correctly.
These products used in the grey tank combat odors in any motorhome or trailer septic system.
Do I Need An RV External Holding Tank?
You only need an RV external holding tank (also known as an RV portable waste tank) if you need to dump at a distant dump station before you want to move your RV.
There are many brands available, some better than others. (See the RV portable waste tank reviews.)
These portable waste tanks allow you to dump into the external tank and then transport that tank to a proper RV sewage system dump.
I've never used one in my 5.5 years of full-time travel, but if you're stationary, more often than not, it might be good to have an external camping waste tank. Especially if the places you stay don't have sewer hookups that allow you to dump your RV directly into the ground without moving from the campsite.
Conclusion
In order to use your RV holding tanks without issue, there are a few key things to know about them.
Mostly, you should follow rules for your black tank so it doesn't get a clog, and make sure to occasionally sterilize your fresh water tank.
Holding tanks for travel trailers and motorhomes must be dumped when they are full or close to full. You do this at any dump station or other approved waste facility.
Figuring out your RV holding tanks isn't rocket science, but yes, you should educate yourself about a few aspects so they keep working as they should.
Don't be scared, just get out there and start using yours. You'll figure it all out as you go.
Learn something from this article? Yay! Learn more about RV basics on Camp Addict.
Author: Kelly Beasley
I dedicated myself to living the full-time RV life for over 6.5 years, immersing myself in the unique quirks and joys of the boondocking lifestyle and gaining a wealth of knowledge and experience along the way. In December 2020, my business partner and I made the transition to part-time RVing, but in January 2023, we hit the road once again, this time in our trusty vans. My mission is to help others embrace the RVing lifestyle with confidence and excitement, armed with the knowledge and resources needed to make the most of their adventures. I believe that the more you know, the more you can truly appreciate and enjoy the freedom and flexibility of the open road.
What is the potable water tank for?
Hi Jack,
It’s a tank that provides you with running water when you are not connected to an external water source. Must use your water pump to get it through the toilets and faucets.
I’m your eternal pundit I guess;
1) RV sewage systems are not ‘septic’ systems and using that word is best not done. Septic systems are a) large, b) separate liquid and solid waste AND c) provide time and space for the biological digestion of solid waste, and d) allow liquid waste to percolate into the ground. There are some variations but all have these features. None of these apply to the RV SEWAGE HOLDING TANK SYSTEM.
2) Test the TP you want to use by placing it in a ziplock with water. If it becomes particles floating in water overnight, it will do the same in your RV HOLDING TANK.
3) It is NOT ILLEGAL to dump either gray or black tank waste in either a porta potty or vault toilet. Both are APPROVED for storage of sewage. It is likely against the RULES of whoever owns the system though. Breaking the rules, may get you expelled, but they can’t ‘legally’ fine you unless they somehow have enough leverage to extort you.
4) I have a macerator pump that allows me to pump/dump sewage (black or gray) in a pit toilet and I have done so with black on some occasions.
5) The contaminated water in your RV ‘gray tank’ is considered by the government to be sewage, not gray water. By legal definition, gray water contains only dissolved contaminants (soaps, etc.), not suspended particles (food). For your RV ‘gray water’ to become legally definable as gray water, you need to filter out all the particles in it that are (typically) sink wastes.
6) If you were to dump shower water directly onto the ground, this is an example of true gray water dumping and is legal in some small percentage of municipalities (although generally only on your personally owned land). This is why ‘shower tents’ or outdoor showers are legally and procedurally allowed (but only with biodegradable soaps).
7) Of all the federal land-owning entities (there are 6), the only one that permits the dumping of gray water is BLM and then, only in states that allow similar dumping on state land. This is actually pretty rare and I contend, that most surface dumping of any kind is illegal (but rarely either understood or caught) and immoral. Trashing campsites that leads to their closure includes dumping of waste that attracts insects and animals which both forms of sewage do.
Thanks for the wonderful comment, Steve! As usual, you offer incredible insight and knowledge, which is greatly appreciated!
Regarding the use of ‘septic system’ on this page, we do so as that is a term that is used frequently by people searching the subject. At Camp Addict, we strive to provide the best information on subjects people are searching for. To do so, we must be discoverable on Google, which requires us to use terms that people use to search for information (whether the terms they use are technically correct or not).
You bring up a great point, so I added an information box to clarify what we mean when we use the term ‘septic system’ in reference to campers.
Can I get this by mail?
Hi Wellington,
What exactly were you looking to buy?
Here at Camp Addict, we don’t directly sell anything. Rather, we provide information and product recommendations.
Any products that we recommend have a link (generally an Amazon link) that takes you to where you can purchase the recommended product.
On this holding tank page we don’t have any of the ‘buy links’ as it is purely an information page.
Hi Kelly, My husband and I always look forward to receiving your newsletters!
Question: What are the pros and cons for using a composting toilet?
Thanks!
Hey Jenna,
Glad you enjoy our newsletters!
While neither Kelly nor I have any personal experience with composting toilets, our toilet guide page has a section written by experienced composting toilet users which has a pros and cons section at the end.
I hope that helps and thanks for being a loyal Camp Addict reader!
Kelly i have a class B and i tried your idea from long ago of putting toilet paper now graduated to paper towels in a plastic bag instead of flushing . like you said no smell and so easy to handle[no pun] and knock on forehead have had no more clogging issues in black water tank. thanks as always for going where no man has gone before.
Hi Douglas!
Yep! Another happy customer! LOL!
Once you get beyond the idea that it’s a ‘gross’ thing to do- put TP into a trash can, you see how wonderful of an idea it is! Saves black tank space, doesn’t stink, and NO fear of clogs. You have a little more trash than you ordinarily would, but my trash (and TP usage) is so minimal that it doesn’t make much difference.
Thank you for letting us know that you tried it and for sharing your results!
Is it illegal to dump my black water into a port a pottie?
Hi Al,
I would think it would depend on where the port-a-potty was located. In other words, different locations may have rules against dumping black tanks in a port-a-potty. Plus, that’s a good way to fill up a port-a-potty since they don’t have that large of a holding tank.
Also, you would have to find a port-a-potty that was lower than the outlet of your black tank as liquids don’t tend to like to flow uphill.
A normal dump station would be your best option. But I’m guessing there is a reason why you are asking this question. 🙂
My wife and I are wanting to go full time RV for a few years while we save to build. We have the property but no septic and won’t for a while. We have questions on how to handle this.
Two options are a 300 gallon above ground black water storage tanks or just pulling to a local dump station when needed.
I would prefer not to have to break down camp. We need some guidance on best way to handle it?
If we go with a 300 gallon or larger above ground black water tank are there companies that will come pump when needed?
How frequently would we have to have a 300 gallon black water tank pumped with 2 adults?
What would that probably cost per pump?
Or is it a better idea to just take it to a local dump station?
Any other suggestions are appreciated
Thanks in advance for your time and guidance! Great website!
Hi Daniel,
Glad to hear you like Camp Addict!
300 gallons is a good sized black tank option. If it’s above ground, are you going to be able to transfer from your RV to the tank via gravity alone?
I suppose you could use a macerator pump setup in order to pump ‘uphill’ into the tank if needed.
I have a 45 gallon black tank and I can go 1 month+ between dumps with it. But I’m a single person, make sure I don’t let excessive water flow into the black tank when I flush, and pee outside whenever I can when I’m boondocking.
How long the two of you can ‘last’ with a 300 gallon black tank is going to depend. It’s something that time will tell.
There are companies that will pump out tanks, such as a septic tank pump out service, or a company that pumps out porta potties. You would have to check in your local area to see what is available and if they would accommodate you.
I agree that having to go to a local dump station would get old fast, so if you could come up with an on-site solution, that would be best.
Another option (though obviously cost more money) would be to have a drain field installed ASAP, with an RV dump station near where you plan on parking your rig, allowing you to dump whenever you want. And this assumes you would be installing a drain field at the property you are building on.
There is definitely a solution to your problem. You may have to get creative, but it sounds like you are doing that.
I don’t have experience being stationary in one spot for extended periods of time, so I may be missing some other solution.
My husband doesn’t have a septic hooked up. He is just sticking the hoses in the ground what happens by doing this. Scared Wife.
Hello Scared Wife,
Yikes! Your husband is dumping the black (toilet, aka raw sewage) waste tank directly into the ground? Um, this isn’t good. Besides probably being illegal (no clue where this is happening, but I do believe most locations frown upon this type of activity), it has the potential to create a big stinky mess and potentially attract unwanted wildlife.
Why is he not taking the RV to a dump station or other suitable place to properly dispose of the waste?