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What Is an RV Gray Water Tank? – A Detailed Answer

Writen by Tom Hank

Fact checked by Joseph Varney

what is an RV gray water tank

It can be tough to care for an RV’s plumbing system since its framework isn’t simple. For instance, RVs generally have gray water tanks to hold some of the water in the rig. But what is an RV gray water tank?

An RV grey water tank is a reservoir to collect used water from plumbing fixtures. However, it doesn’t hold water from an RV toilet.

Take note that there’s more to a gray water tank for RV besides its general description. Continue reading to gain additional insight into this water reservoir, which should also help you in caring for it.

Table of Contents

What Is a Gray Water Tank?

A camper grey water tank provides storage for water from the RV’s plumbing fixtures like the sink and shower drain.

So if a person uses the RV’s bathroom or kitchen sink, the water goes to the gray water holding tank. Some dishwashers and washing machines for motorhomes can also connect to this container for relatively easy water disposal.

What’s the Difference Between RV Gray and Black Water Tanks?

While a gray water tank for camper holds water coming from fixtures like the RV’s sink, the black water tank holds wastewater from the vehicle’s toilet. It also means that water in the black tank will generally be dirtier than the content in the gray container.

What Is the Average RV Gray Water Tank Size?


The average gray water tank size in a camper often depends on the vehicle’s class. Class A and fifth-wheel trailers typically have larger gray water tanks than Class B motorhomes.

Here’s a quick look at the different camper classes and their average gray water tank sizes:

  • Class A: 40 to 65 gallons
  • Class B: 8 to 35 gallons
  • Class C: 31 to 91 gallons
  • Travel trailers: 28 to 78 gallons

How Do You Know When Your Gray Tank Is Full?

Generally, two relatively common indicators can occur if the RV gray water tank becomes full.

First, water is pooling at the sink or shower drain. Water may still go down this area, albeit at a snail’s pace.

The other indicator is when the LED warning light from the gray water tank’s sensor lights up. Take note that each RV may have different locations for this light. So it’s best to check your vehicle owner’s manual to verify the LED’s whereabouts.

What Happens When the Gray Water Tank Is Full in an RV?


Rig owners that leave their gray water tank unchecked and allow it to overfill may run into issues. One possible problem is water backing up the sink or drain.

Keep in mind that water from the gray tank may not be as filthy as the moisture in the black water tank, but water backing up from the gray tank can still leave a mess that might be tough to clean.

How to Empty Gray Water Tanks?

Draining the gray water tank is important to prevent RV users from encountering certain problems with their vehicles’ plumbing. But a time may come when the sewer draining system is still relatively far away.

If you have this concern, the following guide can help you in this regard:

What You’ll Need

  • Funnel
  • Portable jugs or containers
  • Hose (don’t use one reserved for fresh water)

Quick Step-by-Step Guide

  • Step 1: Locate the gray water tank in your RV.
  • Step 2: Connect the tank’s drain line to the hose and funnel, which should lead to the jug or container.
  • Step 3: Slowly pull the gray lever on the tank to allow water to escape to the container.
  • Step 4: Shut off the drain lever and replace the container once it’s about 3/4th of the way full.
  • Step 5: Keep the containers in a proper storage space.
  • Step 6: Dump the gray water at an appropriate location once you reach that area.

Can You Leave Your RV Gray Water Tank Open?

RV owners can leave their gray water tank valves open, provided they connect these containers next to nearby sewer connections. That way, water can run freely from the vehicle to the sewer line.

How to Stop an RV Gray Water Tank From Smelling?

Gray tank wastewater can create an off-putting scent if things like food go down the RV’s drain. If this event happens, installing a new air admittance valve may solve the problem.

But what if you’re far from a plumbing store? If so, here’s a temporary fix if a stench is emanating from your RV’s gray tank.

What You’ll Need

  • Rubber band
  • Ziploc bag

Quick Step-by-Step Guide

  • Step 1: Locate the air admittance valve in the camper, which should usually be underneath the sink.
  • Step 2: Place the Ziploc bag over the valve.
  • Step 3: Close and secure the bag’s opening with a rubber band.

If done properly, the bag should contain most if not all of the unwanted smell from the gray water tank. But you may still need to replace the air admittance valve when you have the chance to enjoy a long-term solution.

Frequently Asked Questions

How Long Does A Gray Water Tank Last?

An RV’s gray water tank will usually last about 2 to 3 days before it needs draining. But the frequency to drain this reservoir still depends on the usage.

Rig owners may need to remove water from this tank sooner than later if they shower, wash the dishes, and dispose of water frequently. The size of the tank also plays a vital role in providing an estimated time to drain the water from the container.

How to Clean RV Gray Water Tanks?

An inefficient gray water tank in a camper may lead to serious problems. Draining the tank can help prevent these issues from appearing. But some wastewater residues may remain, which can still promote concerns if left unchecked.

For example, the sensor light on the RV gray water tank might continue to stay on even after draining the wastewater from that container. If so, here’s how to clean the sensor and remove this malfunction:

What You’ll Need

  • Liquid dishwasher

Quick Step-by-Step Guide

  • Step 1: Pour a cup of liquid dishwasher detergent down the sink.
  • Step 2: Flush the detergent with significant amounts of hot water.
  • Step 3: Drain the wastewater from the gray water tank.
  • Step 4: If the LED indicator remains lit, repeat steps 1 to 3 until it turns off.

Can I Put Bleach In My Grey Water Tank?

You can put bleach in your RV’s gray water tank to sanitize it. Make sure to only put a cup of bleach per 15 gallons of stored water.

For example, 20 gallons of water in the gray tank should only need a 1-1/3rd cup of bleach to sanitize. Using less bleach than ideal may not provide satisfactory results. On the other hand, applying more bleach than needed may damage some parts.


By now, you should know the answer to the question, “what is an RV gray water tank?”

It’s also important to know how to maintain this water tank. Failure to care for it properly can lead to problems, such as water backing up the plumbing system. Don’t forget to drain the wastewater in this container to prevent such issues from occurring.

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