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What Happens When My RV Grey Water Tank Is Full?

While on the road for vacation and relaxation, your RV Is like your home, but just a bit different. Most homes have a plumbing system that brings in fresh water and removes drained water through pipes that lead underground.

RVs are different. Waste water is generally stored in tanks that are located underneath the RV. These tanks are more like septic tanks for homes without city sewers. They do require emptying often.

Grey water tanks do get full. You’ll be able to tell in a couple of days, including your RV plumbing not functioning correctly. We offer some ideas below on what to look for and what to do about your grey water tank.

First, what is the grey water tank?

Your RV should have three tanks: fresh water, grey water, and black water. We are talking about the grey water tank in this article. The grey water tank takes the drained water from your sink and shower. 

The water in your grey tank can be gross, though not as gross as your black tank. Your black tank takes waste from your toilet.

How can I tell if my grey tank is full?


Many RVs have built in sensors that tell them via a display on their smartphone or the vehicle dashboard about tank capacity. These normally indicate in quarters (¼, ½, ¾ and full) how full your gray water tank has become. Sensors are fairly accurate though they can wear over time.

Still, draining your tank early is much better than draining your tank too late. 


Your RV plumbing system sends the waste water to one place and doesn’t remove that water till it’s drained. If you have too much grey water in your tank, you’ll know right away if your shower or sink stops draining.

This isn’t an especially fun way of learning you need to drain your tank considering that you are probably in the middle of something. You might even think the line is clogged at first. Between checking the line and seeing if your sensors are working, this can be a little confusing too.

Also of note, the water will come out of the drain that is closest to the grey water tank. Check this drain when you think water is getting full. This drain should be bubbling out water whether or not you are using it.

You can wait until its near full

There is a small upside to waiting until your grey water tank is nearly full. First, having grey water coming up through your drain doesn’t present an immediate threat to your health. Second, a full grey water tank is actually faster to drain.

Water carries weight and will push down faster. You’ll find that you won’t save a lot of time, but considering that you have other things to do, you might notice the difference.

Draining the grey water tank

Whether your sensors told you the grey water tank is full, the timing was just right, or you discovered waste water in a drain – you’ll want to drain your tanks.

The biggest factor in draining the grey water tank is finding an RV park in most situations. Some states allow you to dump grey water in non-sewage places because the water generally doesn’t contain human waste. Check with your local authorities to see what is possible.

Find an RV park near you. You might need to use the Internet to search for one. Also, ensure they have functioning sewer receptacles – it’s not guaranteed!

How to drain the grey water tank

The first thing you are going to need is to know where your grey water tank is located on your RV. Pull up to the waste water receptacles at the RV park with this side closest to the receptacles.

You’ll need a hose and you might want disposable gloves. After all, you might as well drain your black water tank while you are here. For the purpose of this particular article, we are only discussing the gray water tank draining though the method is the exact same. Note that if you are draining both the grey and black, do black first to let the grey water rinse the hose.

Remove the cap on the receptacle for the grey water waste, this should be in the ground and probably in concrete. Push one end of the hose into this receptacle.

Uncap the grey water tank underneath your TV. Slip the hose in right away. After slipping the hose in, you can find the tank valve. The valve is often a step that can be pulled or circular like a spirit. Turn this until you can hear your water flowing.

Once the tank is empty, remove the hose from your RV first then recap the tank. Remove the other end from the receptacle then cap that too.

Your tank is now drained! Put the hose itself away – you could also consider rinsing this with fresh water if there is any available. Grey water is often used to rinse black wter, but could use a rinsing itself sometimes.


There are a few obvious signs that your grey water tank is full and needs emptying. Between having your drains produce water and having the drain run slow, you’ll hopefully see an issue even if your sensors don’t.

Thankfully using some directions and a hos, your grey water tank can be quite easy to drain. You need only find a place to drain the tank and have a few minutes. Your RV and passengers will also appreciate being able to use the RV like a home on a regular basis, even if it means a little maintenance. 

Waiting for the RV to drain also means having a few minutes to relax and potentially fill up on gas, fresh water, or anything else that your journey needs.

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