Black Water Tank Not Draining

November 9, 2022

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The Black Water Tank On My Rv Will Not Drain

How to: Clogged black tank fix – works EVERY TIME!

I have an 18 foot Coachman Catalina Travel Trailer. The black water tank doesn’t drain, meaning I have to siphon it out every 3-4 days. Does anybody have any ideas what the problem might be and what options there are for repair?ANSWER: Greetings Greg thanks for submitting your question on our Ask An RV Question Page.With the information you have provided me I really cannot tell you the exact problem with your Black Water Holding Tank. If it is because the Holding Tank Dump Valve is not opening and closing, you will probably end up having to replace the Dump Valve.In some cases the holding tank itself could have a blockage in it. Sometimes using Holding Tank Waste Digesters can clear up the blockage. If all else fails, you may have to take the trailer in and have the holding tank dropped and cleaned out manually.We have all kinds of information on holding tank care and maintenance on our website you might want to review the answers I gave to the questions listed below to get further information.

Black Water Tank Not Draining On My New 369rl

I just tried to drain my black water tank for the first time this past weekend.Can someone tell me how to properly use the flush out for the black water tank? A note near the water connection says not to use it without having the “#%” valve in the open position. I don’t remember the reference used for the valve name but whatever the name was it wasn’t labeled on any other valves in the compartment. Very confusing.I did run water to the flush valve because I of course wanted to flush the tank after draining it but when I opened the black water tank drain valve only a very small amount of the contents came out and that was in a small stream rather than in a big WOOSH like I’m used to with my previous trailers. After a while the stream stopped and I was left with 2/3 of the tank contents still in the tank according to the gauges inside.This is my first 5ver so I don’t know anything about how the utilities are configured. I crawled under the trailer to try and look at the actual valve to see if the lever was fully extending but of course all I could see was the black underbelly material that I suppose is part of the winerizing?Anyone have an idea about how I should start troubleshooting when I visit my trailer again this weekend?Thanks,

Norcalrv1 said:07-22-2015 05:01 PM

Get a flush king and you can back flush the tank and then drain itI have used it many times to clean black tankWorks greatSent from my SM-G900V using Tapatalk

Types Of Rv Toilet Clogs

Types of RV toilet clogs:

Paper Towel Clogs: These clogs are caused by people flushing paper towels down the toilet. They can quickly cause a blockage in the RV toilets plumbing.

Human Waste Clogs: These clogs are caused by people not properly disposing of their human waste. This can cause a nasty smell and attract insects.

Foreign Object Clogs: These clogs are caused by people flushing objects down the toilet that shouldnt be flushed. This can cause serious damage to the RV toilets plumbing.

Hair Clogs: These clogs are caused by people allowing their hair to go down the drain. This can quickly cause a blockage in the RV toilets plumbing.

Grease Clogs: These clogs are caused by people pouring grease down the drain. This can cause a slow drain and eventually a blockage.

To avoid these types of clogs, it is important to only flush human waste and toilet paper down the RV toilet. Additionally, it is important to dispose of grease and hair properly. If a clog does occur, it is important to contact a professional to have the RV toilets plumbing inspected and repaired.

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How To Dump Out An Rv Black Water Tank

Emptying out an RV black water tank is easy, but there is a specific method youll need to follow. Youll want to wear gloves and keep the sewer hose away from your face to avoid inhaling sewer gasses.

Connect your sewer pipe to the RV holding tank connection.
Connect the other end of the pipe to a sewer drain.
Open the black water valve to allow the tank to empty.
Flush your toilet continuously for one minute.
Close the black water valve.
Open your gray water valve and allow the tank to empty.
Close the gray water valve.
Disconnect the sewer pipe from the RV and flush it out with a hose.
Disconnect your sewer pipe from the dump station and stow it away.

How Can You Clean Out Your Black Tank

635 Gal Black 550 Gal Tank Spill Containment Unit

Three ways to clean your black water tank are:

Add a cup of liquid laundry detergent, or dissolve a pod of detergent in two cups of hot water, mixed with two cups of water and a cup of dissolved water softener granules or soda to the tank. The softener acts as an emulsifier, removing waste that adheres to the corners and walls of the tank. Fill the tank with water through the toilet, then drain as you normally would. Make sure that you also bleed the grey water tank into the drain as the solids tank empties, to act as a venturi, drawing the solids mix along. The greywater already will have soaps in it.

Use a pressure washer or garden sprayer to reach accessible parts of the tank through the toilet. Once the tank is drained, place a pail under the drain vent and carefully spray water into the drain line with the gate still open.

Regular cleaning involves making sure the gate valve is closed, cleaning the toilet, flushing water into the tank to about the halfway level, letting it sit for several hours, and connecting your garden hose to the backflush connection. Drain the tank, then flush water through using the garden hose until the water runs clearer. Close the valve, fill the tank and let it sit for an hour or so. Then drain, noticing if it is fairly clear. Do not leave bleach in the system, as it may dry out the gate valve. Follow these procedures to drain your tanks.

Recommended Reading: Baking Soda And Vinegar To Unclog Drain

Upgrade To A Macerator Toilet

RV macerator toilets have a built in motor pump and set of blades that grinds up the waste in your toilet before sending it to the black tank.

Reducing the solids in the black tank, especially toilet paper wads, will prevent clogs from happening in the first place. See my introduction to RV macerator toilets for more in-depth details.

How To Maintain A Healthy Blackwater Tank

Congratulations! Now its time to figure out why you had a clogged black tank pipe and learn what it takes to prevent future clogs. There are a few things you can do to maintain a healthy blackwater tank.

The first step is to practice proper wastewater disposal. This means only flushing human waste and toilet paper down the toilet. Additionally, it is important to dispose of grease and hair properly.

The second step is to empty the tank on a regular basis. This will help to prevent clogs and keep the tank clean.

The third step is to use biodegradable products. These products will break down quickly and wont cause clogs.

The fourth step is to avoid non-flushable items. These items can cause serious damage to the RV toilets plumbing.

If a clog does occur, it is important to contact a professional to have the RV toilets plumbing inspected and repaired. By following these steps, you can help maintain a healthy blackwater tank.

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Flushing A Black Tank With Pressurized Water

Using a wand that can enter and spray water all around your black water tank should flush out any clogs and loosen any built up solids from your tank.

The Camco swivel stick is one of the most popular products for this use because it has a rotating spraying head and an on/off valve on the handle.

Connect your sewer hose to the RV and dump station.
Open your black water valve.
Connect your swivel stick to a water supply using a hose.
Hold open the toilet flapper and insert the wand down into the black tank.
Turn on the valve and move the wand up and down inside the tank to rinse away any clogs and buildup.
Turn off the water valve and remove the swivel stick from the tank and toilet.

The swivel stick comes in a rigid and a flexible option to suit the setup of your toilet and tank system.

If you have a tool like the swivel stick its a good preventative maintenance step to use it after every couple visits to the sani dump. Give your tank and sewer pipe a rinse after you dump but while youre still connected to the drain pipe.

Rv Black Tank Flush Kit

Easy! RV Black water tank unclogging

Our final DIY suggestion? Flush your black tank out.

If you dont have one built into your rig, grab an RV black tank flush kit.This simple device twists onto your RV dump pipe. After attaching it to the pipe, you will attach a sewer hose to the other end, add a water hose to the back-flush device, open the RV black tank valve, turn on the water, and allow the strong spray of water to break up your clog.

Please note that you will need to be careful flushing your tank when a clog is involved. If flushing doesnt work right away, you might just end up with too much water in your black tank and a stinky mess inside of your RV.

Recommended Reading: Matte Black Shower Drain Cover

Adding Clog Digesters To The Black Water Tank

Adding a liquid holding tank treatment like Unique RV Digest It will eat away at the poop, paper and other solids inside your black water tank and free up any clogs quickly. Because it is a blend of microbes and enzymes it wont damage the materials of your RV sewage system like some harsh chemicals can.

Hold open your toilet flapper with the flush handle or foot pedal.
Add the recommended amount of RV Digest It.
Wait a few hours for the clog to be consumed and liquified.
Connect your Sewer hose to your rig and a dump station.
Open the black water valve and the clog should be cleared.

This type of treatment will also help keep the sensors and seals in your tanks clean and prevent leaks and electrical faults due to sewage buildup. It also does a great job of eliminating odors from wafting out of your holding tanks without the use of perfumes or obnoxious scents.

Whatever brand you choose to use, just make sure they are septic-safe, or they could ruin the wastewater system of your RV.

Vinegar And Baking Soda

Again. Please. Maybe try pouring this onto some dog poo and see what it does. It will be a whole lot of nothing. Don’t waste your time.

If you think some tiny bubbles are going to move sh**, you’re wasting your time. Besides, the reaction that causes the bubbles lasts for a very short time.

No, this one is not going to work.

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Final Thoughts On What To Do If The Black Or Grey Waste Tanks Wont Drain

Things go wrong with RVs, travel trailers, and 5th-wheels all the time.

Ive had to fix almost everything on my used travel trailer even after just a year of owning it. Having clogged holding/waste tanks is just another part of RV ownership.

Hopefully being able to go camping or travel the world in an RV makes up for all of the problems you experience along the way.

There are things you can do to properly maintain RV holding tanks so you never experience any clogs. You can read about that in this article here.

I hope at least one of these methods has worked for you and you havent given up on camping or RV life.

As a reminder, if you have bought a used RV whether it was from a private seller or a dealer make sure you fill the holding tanks with water and dump your RV before taking it camping.

You never know how someone else has treated their RV holding tanks and you can hopefully avoid any future clogs by cleaning your holding tanks really well before using them.

Have any more questions about RV black or grey tanks and fixing waste tank clogs? Leave a comment below.

The Broom Stick Method

This technique is probably my least favorite method since it can be messy, and you may never want to use the broom again. You dont need a broomstick, but you want something rigid that wont break. With the toilet valve open, stick a long rigid pole down into the tank and push things around.

This technique will only work if you have a straight opening into your RV toilet holding tank. If the clog is within reach of the stick, you should be able to break it up and solve your problem.

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Check The Drain Valve

Before attempting to actually unclog the RV grey tank, you should check the drain valve to see that it is functioning properly. When you turn the handle for the drain valve on the outside of the drain, this would translate to movement on the inside.

However, if the handle or the drain valve is broken, turning the handle might not cause the valve to open. If this is the case, then you will need to repair the drain valve handle and the valve itself.

However, this is something that is quite difficult to do. If it is the drain valve handle that is broken, you may require professional assistance.

That said, if this is not the problem, then you definitely have a clog in your RV grey tank. Generally speaking, its much more likely that your RV grey tank is clogged than the handle being broken. Therefore, lets move on and figure out how to actually unclog an RV grey tank.

Pour Boiling Water Down The Toilet

This is a technique thats been used by experts for decades because it is simple, easy, and anyone can do it. Also, it does not require a technical hand.

Turn off the fresh water supply to the toilet, if possible.
Hold down the flush handle or pedal to open the valve to the black water tank.
Pour a few pots of boiling water into the black tank.
The hot water should accelerate the breakdown of the solids clogging your RV black tank.

I recommend doing this at night so the waste has time to soak undisturbed in the hot water. Keep in mind that if your tank is full, the water wont heat up as much as if it were ½ to ¾ full.

Also Check: How To Clean Drain In Kitchen Sink

Compacted Tank Or Hardened Solids

It’s not super likely, but it’s possible that if you don’t use enough liquids, a mass of solid matter could accumulate at the bottom of your RV toilet holding tank.

Similarly, if you store your RV for long enough with contents still in the RV’s black tank, the liquids will eventually evaporate out.

This practice leaves the solids in there, and eventually, at worst, they will dry and harden.

What Do You Do When Your Black Water Tank Is Clogged

Clogged Black Water RV Tank, Free Quick Fix

How to Clear a Clogged Blackwater Tank: Step by Step

Using a pressure washer or power washer: This sounds like a good idea on the surface, and some so-called RV experts even recommend power-washing your blackwater tank as a first step.

Using pressurized air: Again, pressure of any kind is a no-no.

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What Happens When Your Grey Water Tank Is Full

If the grey tank on your RV is full, the water will no longer be able to move down the drains from your shower, sink, and toilet.

Generally speaking, that water is going to back up, and this means that it is going to come out of the drain that is the shortest distance from the grey water tank.

If you see water backing up in the sink or shower closest to the grey water tank, then you know what the issue is.

How To Clear An Rv Toilet Clogged Pipe

This type of RV toilet tank clog might act like having a poop pyramid.

However, if you DID NOT leave your blackwater tank open while connected to a sewer, and you DO NOT have a black RV tank leak anywhere, a toilet that won’t drain out the sewer line means a clogged pipe.

Here’s how to unclog an RV with a clogged toilet pipe.

Try plunging it. If the pipe is indeed clogged, this method works. Still, it may not push out the blockage.

If that doesn’t work, pour your enzyme treatment down the toilet and let it sit for the time the manufacturer says to leave it.

After the time allotted, flush and see if it works. If not, try plunging again. Repeat the enzyme treatment until it successfully eats through the clog.

If it still won’t flush, get yourself a PEX pipe and try pushing it through into the black tank.

Once the clog clears, fill your tank with water and flush to get any remaining ‘stuff’ out.

Also Check: Rough In For Toilet Drain

Why Is My Rv Black Tank Flush Not Working Solved

9 reasons why your RV black water tank flush is not working are:

Seized drain gate valve. This usually is caused by waste drying out at the edges of the valve seat.

RV is not level. RV tanks have a slight slope toward the drain, but if the RV is not level, waste will not flow toward the exit pipe.

Design of tank. Older tanks were boxy and flat, and solids merely sat where they fell.

Excess paper or solids. Using too much paper or using paper that is not biodegradable causes sludge to build up, particularly around the valve where it might catch on any edges.

Insufficient flush liquid. To save on emptying a tank, some of us tend to use too little water when flushing the toilet, so the solids are not carried away from where they fell.

Accumulated waste in corners. Because many tanks are rectangular, the sludge builds up in corners over months or years of use.

Dried and solidified waste due to improper season-ending flush. If you do not thoroughly flush your tank at the end of the season, waste will dry and harden in the tank.

Gauge inaccurately showing full tank. Gauges are notorious for giving false readings. Frequently, the gauges show Full when the tank really is empty.

Poor operation techniques. Irregular cleaning and flushing, leaving the gate open all the time, not draining grey water after draining the black to help with the flush, inadequate season-starting, season-ending maintenance, and incorrect day-to-day use all contribute to tank problems.