How Does An RV Septic System Work?

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  • Post last modified:December 15, 2021

If you're switching from a permanent home to a mobile one, it's essential to learn the changes you're making. One factor you're making a significant change in is septic systems. In an RV, how would one typically work? If that's what you're wondering, let's take a look at how it functions.

In an RV septic system, there are three holding tanks. There's a freshwater tank, a graywater tank, and a black water tank. The purpose of these tanks is to hold the sewage until you dump it. Once they fill up, you have to take the RV to a dumping site. This is a basic understanding of how an RV septic system works.

There are still more details to cover. How often would you need to empty an RV septic tank? Additionally, what are some ways to tell when it's time to dump the waste? You might also be curious to know what each tank holds! If you'd like to learn this and more, keep reading ahead.

A man serving RV in dumping station, How Does An RV Septic System Work?

The Three Holding Tanks

Let's go over the three tanks that you will be working with. There's the graywater, freshwater, and black water tanks. 

Woman emptying RV sewer after camping

Fresh Water Tank

As the name implies, the freshwater tank is a holding container for water that will come out of your sink and shower. In general, it will be the largest tank in your RV. However, that depends on the type of RV you own. 

Gray Water Tank

The gray water tank holds the wastewater from showers, kitchen sinks, and washing machines. Depending on how old your RV is - it may not have a gray water tank. 

Black Water Tank

The black water tank is the container you want to ensure works correctly at all times. It's one of the dreaded tanks because all of your sewage and toilet paper goes in there after you flush. 

Keeping Track of Capacity

Since they're holding tanks, you might be wondering how you're going to track the capacity. The time it will take to refill or dump them depends on the size of the tanks. Accordingly, the size of the tanks will depend on the size of your RV.

In general, the holding capacity for freshwater tanks will range between 20-100 gallons. The gray water tank will hold around 50 gallons of waste. Lastly, the black water tank will keep about 18-50 gallons of sewage.

How frequently you need to change them will also depend on your water usage habits. Regardless of the size or practices, you will need to be vigilant on how full it gets. To do so, many RVs will come with a monitoring system to keep track.

The Problem With Monitoring Systems

Like most systems, there's a limit to the accuracy of the readings. As some RV enthusiasts suggest, you're likely to shy away from using the monitoring system because of inaccuracy issues down the line. The solution to this problem is to install an alternative like the Horst Miracle Gauge system. 

However, the price point of a separate monitoring system will most likely scare you away. Fortunately, there are a few ways to tell when the tanks are near capacity without a monitoring system. 

How Do You Know When Your RV Gray Water Tank Is Full?

If your gray water tank is full, the shower pan will be holding water. This situation is a deep indicator that it's time to dump the gray water tank. In other words, you don't want the gray water tank to reach this point. Other RV owners suggest improving your water management if this is the case. 

In addition, the kitchen sink and bathroom sink will be unable to drain - signaling that you need to dump the gray water tank immediately.

At most, you should wait until the gray water tank is 2/3 full before you decide to go to a dumping station. But, how exactly can you tell before it becomes too full? 

The reality is that there's no definite answer to the question. Many factors will influence how long your gray water tank will hold out. Some can last three days until dumping is necessary.

It will take a trial period until you nail down your water management. Only then will you know how long it takes to dump your gray water tank. 

How Do You Know When Your RV Black Water Tank Is Full?

Similarly, it will take a trial period until you accurately prepare for dumping a black water tank. Tracking the capacity for a black water tank is simpler. If it's your first time traveling in an RV, you can comfortably rely on the sensors to tell you when it's near capacity. 

However, if you have slightly more experience, you will need other ways to tell it's nearly time to dump. As some suggest, there are others ways to track the black water tank. The first way would be through sound and visual cues. 

If air becomes trapped when you flush, it will bubble back before it goes down. This issue is known as a splashback. It indicates the tank is nearing capacity. 

You can also use smell. The more the toilet smells, the closer to capacity. Lastly, you can also look down the toilet with the water shut off. It will help you gauge how many days you can last before you need to dump it.

Extending Your Stay

Portable rv sewage tank with hose

You don't necessarily have to dump your waste right away if you have a portable waste tank. These will allow you to extend your stay before you have to visit a dumping station. In some cases, you can empty it into the portable tank and take it with you to a dumping site without moving your trailer.

They come in different sizes. One of the more popular portable waste tanks is the blue boy waste tank. If you want to play it safe and avoid water damage on your first trip, it might be a worthwhile investment. 

How Often Do You Empty the RV Septic Tank?

As we've mentioned, how frequently you will need to dump the septic tanks is dependent on your water management. The size of the tanks and the number of people traveling with you also plays a role. While it might take some time to establish a routine, it will make sense to play it safe first. 

In general, you should dump your tanks every 3-5 days. This timeframe helps ensure you won't have to deal with a stinky bathroom. It also means you'll avoid flooding your floors.

Once you're at the dumping station, there is a procedure you may want to follow. You will have to open the black water valve first. Dump it into the appropriate area until it is empty. Then, open the gray water valve without closing the black water one. 

It will allow graywater to back-flow into the black water tank. This method helps drain out the system of any lingering waste. Once both tanks are empty, you can close the valves. 

How Much Does It Cost To Dump My RV Waste?

Close up of recreational vehicle at sewage dump station in campground

To dump your sewage, you will need to visit a dumping site. You might expect it to cost a fee to dump your waste. The cost will vary from campground to campground. 

Some will allow you to empty your RV for free. The reason could be that you're paying to stay at the campground. In other cases, the cost could be as high as $20-$25. It could also be as low as $5 if you have a membership to a campground. 

Is Septic-Safe Toilet Paper OK for RV?

One issue that might concern you is toilet paper in an RV. As you might already know, RV toilets aren't as powerful as home toilets. So, if you use the wrong type of paper, you might clog your toilet.

If you've already prepared ahead, you might have already seen RV-safe toilet paper that you can purchase. However, the price is what typically scares RV owners away. As an alternative, you might consider using septic-safe toilet paper. 

Is it a worthy replacement? Fortunately, some suggest that it is. Septic-safe and RV-safe toilet paper have the same idea behind them - they break down at an increased rate. Still, if you don't want to take risks, you can test the breakdown rate of the septic-safe paper you plan to use. 

For more information on how to test your septic-safe toilet paper, here's a YouTube video demonstrating the process:

 

Can Graywater Be Dumped on the Ground?

Since graywater tanks hold the waste from showers and sinks, you might get the idea that it could be dumped anywhere. Some would suggest that it's legal to empty it in the ground if it meets certain conditions. As they claim, some park rangers may even allow RV owners to dump it on the ground.

Of course, it's on a case-by-case basis. If you want to avoid trouble, you should ask for permission first. Otherwise, you'll have to dump the graywater in a dedicated utility sink. Some campgrounds will have a dedicated gray water disposal unit you can use.

Can I Put Bleach in My Black Water Tank?

Pouring bleach from a galon

When you're emptying the black water tank, it might sound like a good idea to use bleach to clean the tank. After all, how will you deal with the smell the sewage leaves behind?

Is it safe to put bleach down a black water tank? Some will suggest against the idea because it can potentially damage the rubber seals and gaskets. Alternatively, you can use a less harsh cleaner.

However, if you're adamant about using bleach, you can use a diluted solution. You'll have to mix a 1/4 cup of bleach with one gallon of water. Pour the diluted solution into your toilet and let it sit for 10 minutes. Drain the black tank, but keep the water running until the output is clear.

You will have to take extra steps when dumping this into a dumping site. Some campgrounds might not allow you to empty chlorine bleach into the area. In general, this solution should be safe to dump into an approved dumpsite.

Final Takeaway

Becoming familiar with situations you will have to deal with is the first step to ensuring a successful trip. Maintaining an RV septic system shouldn't be a problem after getting experience. All it takes to ensure an enjoyable journey is responsible water management! We hope you found the information above helpful. 

Before you go, there's still more to learn about the septic system. You will need to visit approved dumpsites to empty the contents in your RV's septic system. To learn more, check out our post - Where Can You Dump RV Tanks?

If it's your first time draining the tanks, you might want to get an idea of how it will go. To learn more about the process, check out our post - How To Drain The Gray Water Tank On RV.

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