Cleaning Your RV Gray Water Tank in 5 Easy Steps

Your RV's gray water tank, where the waste water from your sinks and shower goes, is less intimidating to maintain than your black tank. However, that doesn't mean the gray tank doesn't require some routine maintenance to keep it functional and odor-free. The gradual buildup of grease, soap scum, and food residue can cause odors that rival those of the black tank, and in the worst cases, cause clogs to form. To keep your gray holding tank in top shape, you should clean the tank periodically and add an environmentally friendly treatment for best results.

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How Do I Clean My RV Gray Water Tank?

Add Cleaning Agent
Take a Drive
Drain Tank
Rinse Tank
Add Treatment

Watch now: Our resident expert Jake H. walks us through how to clean black and gray RV tanks

How Do I Clean My RV Gray Water Tank?

Fortunately, cleaning and maintaining your RV's gray tank is a fairly simple process—and a much less unpleasant one than cleaning the black tank. Cleaning your gray water tank involves using a cleaning agent, draining and rinsing the tank, and treating it periodically. For best results, don't wait until your gray tank smells like a sewer to take action. There are no hard and fast rules for how often you should clean, rinse, and treat your tank, but we recommend taking advantage of long drives to use a cleaning agent. We also recommend rinsing the tank each time you dump.

You should also treat your gray tank for best results, although it's usually not necessary to do so each time you dump. Many RVers choose to treat their tanks after every second or third dump. What works for you is a matter of personal preference and depends on your gray tank usage.

There are five main steps required to thoroughly clean your waste tank:

3. Drain Tank

Add Treatment Chemicals to your RV Gray Tank

Learn more about each step below.

1. What are the Best RV Gray Tank Cleaning Methods?

The best way to clean your RV's gray water tank is to let the RV do most of the work. Fill your gray tank at least 1/2 full of water, then add your cleaner of choice. This is best to do before you hit the road; driving will cause the soapy solution to slosh against the tank walls and eliminate buildup. This is also great for cleaning your sensors.

Check out some popular household RV cleaning agents, below:

GEO method: 1/2 cup water softener (liquid or powder - Calgon is most common) + 1/2 cup laundry detergent or Dawn dish soap

1/2 to 1 cup Dawn dishwashing liquid (blue Dawn is particularly popular)
1 cup Calgon or other water softener
1 cup baking soda
1 cup dishwasher detergent gel
1 cup laundry detergent

Steradent denture cleaner
Napisan stain remover
Water: Some RVers choose to forgo cleaners and chemicals in favor of a water-only method. If you choose not to clean your tank with soaps, cleansers, or detergents, be sure to still rinse the tank thoroughly using one of the methods discussed below in the section "How Do I Rinse My RV Gray Water Tank?"

Bleach

If you ask a group of RVers how they clean their gray water tanks, at least a few will probably claim that bleach does the trick. However, keep in mind that bleach can damage your RV's seals and gaskets and kill off useful bacteria needed to help break down waste. In fact, many RV owner's manuals warn against using bleach in toilets and drains. For these reasons, bleach is not recommended for use in your gray water tank—particularly not when there are so many safe, simple, economical alternatives.

2. Take a Drive

After filling your tank with water and cleaner, take a drive. The movement of the RV will cause the water to slosh around the gray tank and remove buildup. If possible, it's best to let your cleaning agent soak in your tank for 24-48 hours before draining.

3a. How Do I Drain My RV Gray Water Tank?

Draining your RV's gray water tank is just as easy as (and less gross than) draining your black tank. Simply connect your sewer hose to the designated dump station hole, connect the other end to your gray tank valve, open the tank valve, and let things flow.

A few helpful things to remember:

Dump your gray tank after dumping your black tank. The gray water will help wash any remaining residue from the black tank out of your sewer hose.
You can leave your gray tank valve open at the campground, but you should close it when the black tank is nearly ready to dump. This way, when you're ready to dump the black tank, you have enough gray water to flush out the sewer hose.
Scrape your dishes to remove food and grease before rinsing and washing them. It doesn't take much to clog RV plumbing, and food waste is largely responsible for the worst gray tank odors.
Don't dump illegally. This is better known as "stealth dumping" among RVers. Check the rules for any state and campground where you plan to drain your tanks to see what limitations exist.
Use a strainer in your RV sinks and shower to prevent food and hair from going down the drain.

Draining Your RV Gray Water Holding Tank

Gray Tank Dumping Etiquette:

1. Check the rules wherever you go

2. Be considerate of others

3b. Where Do I Drain My RV Gray Water Tank?

Although your gray water tank is not as toxic as your black water tank, gray water is still waste water, and there is a time and a place to dump it. Laws vary by state, so it's always a good idea to check the rules of any location (state, municipality, and campground) where you plan to drain your tank. Dumping gray water on the ground is prohibited in many places but encouraged for irrigation purposes in some others. Secret, illegal dumping is called "stealth dumping" and can result in fines in many locations.

A few things to keep in mind:

If you're at a campground that provides dumping facilities, use them. It may not seem like much to dump a tank of gray water after washing some dishes, but consider the result if all RVers emptied their gray tanks on the campground, week after week. No one wants to camp in a muddy mess of wastewater.
Don't contaminate a freshwater source (the nearby fishing lake is not the perfect place for your shower water).
Don't dump on pavement - gray water can smell as bad as black water, especially gray water containing food waste. If the gray water will pool and become standing water, do yourself and your neighbors a favor by not dumping it.
Some locations differentiate between gray water from your shower/bathroom sink and gray water from your kitchen sink (waste from foodstuffs makes all the difference). (In a similar vein, some RVs have 2 gray water tanks, including one specifically for kitchen waste water.) Be sure to check the rules at any location you plan to dump at to make sure you're not violating any rules.
Essentially, gray tank dumping etiquette boils down to 2 rules of thumb: double check the rules wherever you go, and be considerate of others.

4. How Do I Rinse My RV Gray Water Tank?

After draining your gray water tank, it's also a good idea to rinse the inner tank walls to remove any remaining residue that could otherwise cause unpleasant odors or clogs. To clean the inside walls of the tank, you'll need a flush valve or tank rinser.

Attach a garden hose to the barrel and direct the flow of water where you need it to clean your holding tank and sewer hose.

1. Flush Valve

Flush valves allow you to rinse your gray water tank and flush out your sewer hose in order to break up clogs and clean your tank sensors. Connect a garden hose to the barrel (see image), then choose either the "tank" setting or the "hose" setting to direct the flow of water where you need it. Flush valves also include built-in backflow preventers to keep your water source contaminant-free, so you don't have to worry about waste water backing up into your hose. Many flush valves come with clear barrels so you can see when the water runs clean.

Most flush valves, like the Flush King, attach and detach with each use and require no tools to install. Simply connect one end to your gray waste valve, connect the other end to your sewer hose, and attach a garden hose to the female coupling on the barrel. There are also flush valves available that install permanently by connecting to the tank and outside wall of your RV, such as the Valterra No-Fuss Flush Valve. Permanent flush valves do require some drilling, but these are DIY installations for most.

Featured: the Tornado 360-Degree RV Holding Tank Rinser

2. Tank Rinser

Tank rinsers are permanently installed on your RV and are a convenient way to flush grease, food residue, and soap scum out your gray water tank. Tank rinsers provide an exterior hookup for a garden hose; the other end of the rinser is inserted into a hole drilled into the tank. Once attached to a hose, the rinser then sprays water at a high pressure in order to thoroughly clean the tank.

One consideration to keep in mind when selecting a tank rinser is the nozzle style. Some rinsers shoot straight streams of water, and others spray a 360-degree radius for maximum reach. Some rinser nozzles are stationary, while others have rotating heads to hit every inch of your tank.

Tank rinsers install directly into the tank and provide an exterior connection point for a garden hose.

5. What are the Best RV Gray Water Tank Treatment Methods?

After thoroughly cleaning your gray water tank and removing any buildup from the tank walls, you can treat your tank for best results. It's not necessary to treat the gray tank every time you dump— after every second or third dump is sufficient. Treating your tank helps prevent odors and clogs by breaking down residue such as grease and soap scum.

One crucial thing to remember is that only environmentally friendly treatments should be used—stick with those that are enzyme-based and formaldehyde-free. Many campground dump stations around the U.S. are closing due to uncourteous RVer behavior and the use of harmful chemicals to treat waste tanks. Using environmentally friendly treatments helps keep these vital stations open for public use.

Pure Power Blue Treatment for RV Holding Tanks

1. Liquid Treatments

Most liquid treatments designed for RV holding tanks are chemical-free, biodegradable enzyme/bacterial formulas, which makes them perfect for breaking up waste without introducing harmful chemicals to the environment when you empty the tank. Make sure you use the correct amount of liquid for your tank (check the bottle for measuring instructions)—more is not better.

Liquid sensor cleaners designed specifically for removing buildup from your tank sensors are also available. If you find your gauge readings are no longer as accurate as they once were, a cleaner like TST RV Tank Probe Cleaner can help remove any remaining buildup and improve tank readings.

2. Drop-In Treatments

Drop-in RV gray tank treatments include tablets, pouches, and scoopable additives. Many RVers prefer drop-in treatments over liquid treatments for the convenience factor—unlike liquids, drop-in tablets and pouches don't require any measuring, and you don't have to worry about accidental spills.

Cleaning Your RV Black Water Tank in 4 Easy Steps

How to Unclog an RV Toilet, Sink, or Shower: Pro Tips for Unclogging Any Tank

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Written by: Amber S.

Updated on: 11/5/2018

Howard S.

5/1/2022

Checking out camper for leaks the flush tank line apperently froze and split there is no way to put antifreeze in that line it loops up ins petition and it must have had a air lock not usable any suggestions for repair this is a 202128.5 rats 5 th wheel

David B.

5/2/2022

Hey Howard. Sorry to hear about the damage to some of your plumbing....To get replacement parts I'll need the part numbers off your damaged units... RVs are not made in the same way cars/trucks are. They use whatever parts are available to them. If you can get the part numbers or the diameter and length of the hoses and fittings damaged I can better help you out. I linked a page that has some parts and hoses. If you need anything else let me know, I'll be here.

Helpful Links

search/black+tank+flush+hose

Deborah S.

4/24/2022

We are having an odor inside the RV. It comes and goes. We have the gray water hose open most of the time except when we drain the black tank we drain the gray water after draining the black water. We have never used a tank cleaner for the gray water tank.

David B.

4/25/2022

Hey Deborah, I hear you, no one likes random bad smells. Just follow the steps on our grey tank cleaning guide(linked below), that will help you remove a source of the problem. Also I linked to our page of odor elimination products. I really think you will benefit from the Odor1 products. Check them out! I'll be here if you have any questions about any products.

Helpful Links

dept-pg-odor_eliminators.aspx

dept-pg-rv_treatments-sf-holding_tanks.aspx

faq-clean-rv-gray-tank-in-5-easy-steps.aspx

Joe J.

6/4/2021

You recommend a back flush valve. So I have now emptied my black tank and now emptied my gray tank. If I back flush with that valve and the pipe that leads to it that just had black water in it, isn’t that a problem?

Jon G.

6/8/2021

If you had enough water in your gray tank (like we recommend doing) then anything from your black tank should have been washed out of the system. This means that the flush valve will just be cleaning out leftover debris from your gray tank.

Neil M.

4/19/2021

Hi we have a proublemwith odour in our camper. It seems like whenit get warmer out side the more the smell is noticed.We have cleaned tanks with softwater Calgon and all kinds of store boughttank cleaner it just wont go away.Can fumes back track in to the toulet if your black water bump velve has a drip?Thanks

Jon G.

4/22/2021

If the valve has a drop I would imagine that you could smell something outside but I'm not sure how that would affect the inside of the camper unless the leak originates further up the waste drain system and you are only visually seeing the drip at the valve. Is it a sewer odor or just a bad smell? Mold can be an issue with trailers too sometimes.

Neil M.

4/22/2021

@JonG Thanks for your reply i bought a tank flush and a new dump valve and a ruber for the botem of the toilet i will try that and look for mold. Thanks again

Neil M.

4/27/2021

@NeilM I climed under the camper and there was a drip comeing from the plastic under cover. I cut a hole in it there is mouse and squirl crap and wet think. Riped half of the under cover of scrubed the crap out of every place used javex and water. Put all the insolation and under cover in garbage bags. That was the smell we been looking for.Camper smell way better just waiting to see when it warms up if the proublem is solved.Thanks i was under the camper looking for mold thanks for yourtip.

See All (4) Replies to Neil M. ∨

David B.

6/23/2020

Thank you for the article on tank sensor problems. I am having problems with our gray tank saying it’s 1/3 on gauge. Wife was doing dishes and water come up shower and now knowing the gray tank was full and not ready correctly. I crawled under it and checked connections all good and unhooked all the all 3 plus the ground it still read 1/3. What should I do next? Still put dishwasher soap in and Fill it half drive it and see if that helps? Or do I have other problems? Thank

Chris R.

6/26/2020

I would definitely try cleaning the tank with some dish washing liquid as described above. It's very possible that those sensors are just dirty and not able to properly read the tank.