What Happens When the Grey Water Tank Is Full?

The grey water tank quickly fills up if you're regularly using your sink and shower in your RV. But what happens when the wastewater tank fills up? Here's what happens.

grey water tank underneath rv

There are a few different water tanks in your RV, but the grey water tank is of particular importance. It’s going to hold wastewater from every source in your rig besides the toilet (that duty belongs to the black water tank), which is going to include all showers and sinks.

But seeing how the grey water tank is simply just a tank for holding wastewater, it’s going to reach a point where it can no longer hold any more water until it’s been drained. That then begs the very important question… what happens when grey water tank is full?

Hmm, what does happen when that occurs? Well, past some other critical points of information, we’re going to answer that question to get rid of all the mystery behind it.

What happens when grey water tank is full?

It’s actually pretty simple what happens when the grey water tank reaches capacity, and you continue to use the showers and sinks in your RV without draining the tank. The water needs somewhere to go but there’s no more room in the grey water tank. So, where will the water go?

It’s going to come out of the drain that’s the shortest distance away from the tank itself. Oftentimes, when the tank reaches capacity, you’ll see yourself standing in some dirty water while taking a shower. This is one of the red flags that alert you that you really need to empty the grey water tank.

How do you drain the grey water tank?

The tank isn’t going to drain and empty itself, so you need to perform the task. Here’s the good news, it’s not a complicated endeavor. In fact, it’s pretty darn easy. If you’re at a dump station, you simply need to connect one end of your sewer hose to your grey water tank valve and the other end to the dump station hole.

From there, you simply open the grey water tank’s valve and allow the wastewater to flow through the hose. Yep, that’s pretty much all you need to do. However, there are a few pointers, if you will, to keep in mind when doing so.

Make sure to drain your black water tank before you drain the grey water tank. The reason it’s nice to do it this way is the grey water can help to wash away any leftover residue left in the sewer hose from the black water tank. You will have to store your sewer hose after all’s said in done, after all.

Use strainers in your sinks and showers to help prevent food and hair from going down the drains, and also make sure to scrape your dinnerware in the trash before washing them (again, to prevent food chunks from going down the drain).

Where can you empty your grey water tank?

What happens when grey water tank is full? It’ll need to be emptied. You now know how to perform that process, but where are you supposed to perform that process? The most sanitary and easiest place to do this is via an RV dump station. Outside of most campgrounds, some marinas and truck stops may also have RV dump stations.

However, what happens if you’re boondocking with your RV and you have no feasible means of emptying the tank? Can you just drain and empty the tank on the ground? Well, believe it or not, doing so can be considered illegal depending on where it’s done.

So, if the plan is to just dump the grey water tank on land, you need to make 100 percent sure that it’s legal to do so wherever you are. Some RVers won’t and will just dump it regardless. We clearly can’t do anything to stop you from doing so, but just know that grey water can contain bacteria that can potentially harm animals and plants.

How large is an RV grey water tank?

With a larger grey water tank, you’ll be able to go longer without draining it. Yes, we know, what an obvious statement that was. The reason we bring that up is that not all grey water tanks will be the same size. It depends on the RV that you own.

Grey water tanks can literally range from 10 to 100 gallons, and sometimes even bigger than that. Your common travel trailer is probably going to range anywhere from 20 to 40 gallons. However, it’s the much larger rigs that will often have tanks possibly as large or larger than 100 gallons.

To figure out the exact size of your RV’s grey water tank, consult the owner’s manual and if you can’t find the information there, you can always try to search on the manufacturer’s website.

How long will it take to fill?

It’s going to vary, but you probably expected that. Outside of the size of your grey water tank, it also depends on various other factors regarding how long it’s going to take to fill the tank:

  • The number of people with you: How many other campers are using your RV? Much like in a home, the more people inside, the more water that’s most likely going to be used.
  • How often the showers are used: Taking a shower can waste a lot of water, and how often you take a shower, the duration, and how often others are taking showers can make a drastic difference in how quickly that tank gets filled.
  • How careful you are with water usage: Much like the last point, it really comes down to how careful you are with your water usage. Careless wasting of water will fill the grey water tank quicker, so just keep that in mind.

Most likely, each person using the RV is probably going to use anywhere between 5 to 10 gallons of water per day.

Are there ways to know the grey water tank is full?

Okay, so if you know what happens when grey water tank is full and you know nothing good can come leaving it that way, are there ways for you to be able to know it’s full? Yes, and one of the ways is if your RV has sensors that indicate when your tanks are at capacity.

If that’s not the case, go into your shower(s) and see if there’s any water in the bottom that won’t go down. As alluded to earlier, this is an indication that you know the grey water tank needs to be emptied.

Final thoughts

In the simplest of explanations, what happens when grey water tank is full? It needs to be emptied ASAP. No matter what, you’re going to need to empty that tank unless you want to deal with some annoying plumbing issues. Who wants that?

Thankfully, the process of doing so is quite simple, and there are a few different ways to know when it’s time to do so. Quite frankly, though, there’s really no reason to wait until it’s full. You can empty the tank whenever you want, and it’s good to get in the habit of doing so often while your RV is in use.Also, if you enjoyed this read, you may also enjoy learning how to drain the freshwater tank in your RV. That tank is the friendliest of them all, but it will still need some attention.