RV Gray Tank Valve: Should You Leave It Open or Closed?

“Open or closed?” Campers have been debating whether their RV valves should be kept open or closed since the dawn of RVing. 

Black Tanks:With black tanks, the subject is straightforward, black-and-white, even — RV black tank valves should always be closed unless you’re actively dumping. 
Gray Tanks:But what about gray tanks? Well, there is literally a gray area in terms of when gray tank valves should be open or closed. 

RV Gray Tank Valves: When to Leave Open or Closed?

RV gray tank valves usage depends on your style of camping.

Quick Reference Guide for Gray Tank Valve Usage

• Dry Camping/Boondocking:CLOSED  (It’s the law!)

• Full Hookups/Full-Timers: OPEN

It’s Your Choice!
Ultimately, it’s up to you, but leaving your gray tank valve open on hookups can provide the following benefits:

• Enjoy endlessly long showers

• Comfortably use your dishwasher and washing machine

• Eliminate gray tank odors

• Prevent misreading sensors

• No chance of overflowing

Have Reservations About Leaving Your Gray Tank Valve Open?

If so, you’re not alone, so let me address some of the main concerns I often hear. 

Won’t leaving my gray tank valve open cause clogs, odors, and misreading sensors?
This confusion often arises when you think of your gray tank the same as your black tank, and the fact is, they’re just different. 

• Clogs: Since no solids enter your gray tank, there is no opportunity for clogs to develop. 

• Odors: When liquid freely drains out, odors are less problematic. 

• Misreading Sensors: If no liquid stays inside the tank, then sensors won’t misread from the associated build up. 

“I can’t leave my gray tank valve open, I use the liquid in my gray tank to rinse my black tank hose!”
Leaving your gray tank valve open makes cleaning your black tank hose even easier! 

How? Well, you should always clean your gray tankbeforeyou dump your black tank, which allows you to use the soapy water from that process to rinse your black tank hose more effectively. I’ll show you how this works below.  

“I’m concerned about sewer gases, drain flies, and rodents”
Adding a p-trap to your discharge hose will ensure your RV is free from dangerous, stinky sewer gasses.

If the campground shows signs of sewer flies, though a p-trapcanhelp here, we recommend playing it safe and keeping your gray tank valve closed at these campgrounds.

Oh, and mice or snakes that might get up into the gray tank? Sure, it’s probably happenedsomewhere at some point,but we’ve been doing this for 30 years and have yet to hear a first-hand account of this happening, so don’t worry. This isn’t a real concern!

Why You Should Add a P-Trap to Your RV Sewer Hose

Creating a p-trap in your RV discharge hose works the same way a p-trap works in your sink, acting as a protective barrier between your RV and the sewer. 

Benefits of adding a p-trap to your sewer discharge hose: 

• Increased Convenience: Comfortably use washers, dishwashers, and even take long showers.

• Improved Odor Management: Establishes a water barrier, preventing sewer gases from backing up into your RV’s living space. 

How to Create a P-Trap In Your RV Sewer Hose

I’m happy to tell you that as someone who is not naturally handy, I find this process to be very manageable and easy.

1. Check Campground Rules & Requirements: Some sites prohibit any part of the drain hose from touching theground or camp picnic tables. 

2. Setup Your RV Discharge Hose Support

3. Connect Your RV Discharge Hose & Create P-Trap: Once the hose is connected, dip the hose down, almost to the ground, and back up onto the hose support so it can fill with water. 
   
   
   

4. Run Water Down Sinks or Shower to Add Water to the P-Trap

5. Use Your RV Plumbing Normally 

And that’s all you have to do to — just imagine, full access to your RV appliances and showers without any of the downsides. It’s really a no-brainer!

Effortless P-Trap Setup: MORryde RV Snap Trap

Make the process even easier with the MORryde RV Snap Trap — specifically designed to make the bend in the sewer hose for you!

What Do You Need for Gray Tank Maintenance?

To enjoy all the benefits of an open gray tank valve, you need to establish good habits.

For gray tank maintenance, all you really need is:

• Water

• Grease-eating dish soap (Dawn Ultra is best from our testing!)

• Time  

These simple ingredients not only get your RV gray tank cleaner than any other option but won’t cause damage to your holding tanks and seals. 

Gray Tank Treatments: Don’t Waste Your Money 

Keep in mind,wemake and sell holding tank treatments, so it would be in our best interest to try to convince you to buy our products to treat your gray tank - but that would be disingenuous! 

Here is the honest truth that we’ve discovered throughveryrigorous testing - no “gray tank treatment” works nearly as good as Dawn Ultra.

While the RV community offers great general advice, their recommendations for gray tank maintenance are often inaccurate or unhelpful. 

Avoid wasting time and money on:

• Bold Product Claims: Products that claim to “deep clean” gray water tanks.

• Outdated Methods: Viral techniques are ineffective or potentially harmful, including The Geo Method and the Ice & Driving Technique.

• Harsh Chemicals: Borax, Bleach, and other chemical cleaners can damage RV components. 

How to Deep Clean Your Gray Tank: Step-By-Step Instructions

Cleaning your gray tank is easy and requires very little effort.

The process is the same whether you’re boondocking or on hookups, and we recommend cleaning your gray tank once a week alongside your black tank.

Note: If you’re trying to clean and restore misreading gray tank sensors, the only difference is that you’ll need to repeat this process a few (often 3–4) nights in a row.

>>> Watch the Video Tutorial. 

Step 1: Close your gray tank valve.
Step 2: Fill your gray tank half-full (you don’t have to be precise) with fresh water.
Step 3: Pour 20 ounces (or more) of Dawn Ultra dish soap down your kitchen sink.
Step 4: Fill your tank the rest of the way (you’ll know your tank is full when you see suds coming out of the sink drain).
Step 5: Let the soapy water sit in the tank overnight. 
Step 6: Dump your gray tank the next morning, and repeat as needed.

Note:If you do dump your gray tankafteryou dump your black tank, now you’ll have nice, soapy gray water to rinse your sewer hose!

Important Note When Cleaning & Restoring Misreading Sensors:
Time is not a factor when cleaning gray tanks. 

If you let Dawn Ultra sit in your tank for days, weeks, or even a month, it will not produce better results. Repeating the process is the key for restoring stubborn gray tank sensors. 

Have Questions About Your RV? 

Contact the friendly and professional Customer Support Team at Unique Camping & Marine for answers today. 

About This Blog

My name is Annie, and I’ll be coming to you each month with expert tips and information that benefit all types of RVers. Each piece is written, not by Artificial Intelligence, but by an Actual Individual... me!

I research each subject, consult industry professionals, and verify information with certified RV techs before this newsletter ever reaches your inbox.

If there’s a topic you’d like me to cover—or if you think something should be added to this checklist—feel free to email me.

- Annie