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How To Completely Clean Your RV's Black Water Holding Tank

by Motorhomes of Texas
(Nacogdoches Texas)

How to Clean Your RV's Black Water Holding Tank

How to Clean Your RV's Black Water Holding Tank

This story was submitted on our
RVing Tips And Tricks Page.

Just a couple of tips;

Even if you own a high-end coach like a Newell, Foretravel, or Country Coach and it has a sewer tank flush, it is a good idea to occasionally give the tanks a manual clean out if your built-in flusher is just a sprayer and not a hose inside the tank. If your sprayer is the kind with a hose inside the tank, you should be able to hear it flopping around when in use; however, those sprayers were known to blow the hoses off into the tank.

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I start with an empty tank. Partially fill the tank with 4 or 5 toilet flushes. (Full toilet). Add dish soap or laundry soap with about a quart of bleach or a bottle of Pine-sol. Let it sit for an hour. I use a thin-walled (cheap) 1/2 inch diameter garden hose which has the end cut off. I cut a piece of thin flat plastic and wedged it into the cut-off end of the hose so that the end was stretched. This turned the hose into a sprayer, and with the high pressure where I get my water, after removing my in-line regulator, this hose flopped around like a cat whose tail got caught under the rocking chair. Anything stuck into the end of the hose will work as long as it stretches the end and doesn’t completely cut off water flow. You can experiment with it before putting it to work. What you want is for the hose to flip and flop around a lot (like our politicians). You are not going to use this hose for anything else other than this job.

Feed this hose down the toilet and turn it on full force. You may need to place a wedge into the toilet to keep the flap from collapsing the hose but make sure that whatever object you choose for this job is too large to go down the toilet. You should be able to hear the hose flopping around inside the tank. It will spray into most of the places the built-in sprayer can't reach, which may include the probes for the monitor panel. On units that have multiple probes screwed into the side of the tank, these probes tend to collect toilet paper on them and makes the monitor panel read the tank level incorrectly. Now go out and open the dump valve…this is CRITICAL! Don’t let it go too long, or your tank will fill up, and the commode will overflow. That initial blast will blow your soapy solution up on the walls, and inner roof of the tank, helping dislodge solids. Leave the dump valve open and the hose spraying for 10 or 15 minutes but do not leave it unattended. The hose could creep back up out of the toilet. I have a clear sewer hose adapte that connects my sewer hose to the dump valve so I can see how clear the water is coming out of the tank. I quit when I no longer see any solids or discoloration of the exiting water. When doing this clean-out, wear disposable gloves because you will have to handle the hose when you remove it from the toilet. Wipe the hose with cleaner disinfectant and put it in a marked plastic bag for re-use.

Nothing on earth is going to make the sewer tank smell good but you will have fewer aromatic surprises when you flush your toilet after the clean out. I advise a monthly clean out in summer and using the built-in sprayer each dump. About every other month in cooler weather but you really can’t do it TOO often.

Editor's Note: To learn even more about properly cleaning your RV's Black Water tank you may want to take a look at the video below by RVing Expert Mark Polk from RV Education 101

To instantly download the RV Education 101 Videos available from RVing Expert Mark Polk visit the RV Education 101 Video Download Store

Here are the RV Holding Tank Cleaning Wands and RV Hydroflush Valves that Mark mentions in the video.

Textips from Motorhomes of Texas

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Comments for How To Completely Clean Your RV's Black Water Holding Tank

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Black Tank Cleaner
by: Rick

Thetford Tank Blaster

The best way to clean your black and grey tanks is to use a product that is actually formulated to do just that. Thetford Tank Blaster is specifically formulated to clean both tanks as well as leaving them with a cherry scent. Foaming action reaches extends its reach.

finish tank cleaning
by: Leroy

I have a question about cleaning the black tank. Your system is very logical. What i was wanting to know is when I dump the tank to start cleaning with a tollit bomb, can I put the regular Disolver/deorderizer in with the bomb?

Another Solution to Smelly Black and Grey Water Tanks
by: Jets2Jobs

Calgon water softener

I use Dawn Dish soap and Calgon water softener at 1 cup each into EMPTY TANK. This will help to break up any solids and stuck on toilet paper allowing sensors to show proper levels. Mix both in a pail or other container before pouring into the bowl. Flush with water until you fill the tank, let the mixture set for 2 to 3 hours, then empty.

360' vent caps

It is OK to use any brand of toilet paper as long as it states "septic tank useable. I use the same mixture in gray tanks. One way to help eliminate tank odors is to replace vent caps with the 360' vent caps.

If your grey water tanks show wrong indicating level, pour into each tank 1 cup AUTOMATIC DISHWASHER detergent per tank, fill and drive to next campsite then empty tanks. This should clean sensors of cooking and food grease which will cause wrong indication levels if they're covered by grease.

Ice and Borax
by: Squirrell


my dad taught me that a large bag of ice (20lb) and some borax fill tank at least half full with water.. drive around for a little bit, causing the water and ice to slush around then go dump..

Sewer hook up at a park.
by: Anonymous

DO NOT OPEN THE GATE ON BLACK WATER TANK VALVE AND JUST LEAVE IT . If you do, the liquid will run out leaving solids behind. Soon you have a plugged tank and toilet. Dump the tank when it gets about 3/4 full. Also use a chemical to break down the solids and deodorize your tanks.

frozen hose leading out of tank. I can't get it to empty the tank at all
by: Anonymous

How to unfreeze my hose going to the blackwater , so it will empty?

It worked for me....
by: Karen Pepers

2'6" or how long you need of connect a male hose fitting to each end, get a cheap spray nozzle from dollar store. connect hose to one end, nozzle to the other end, (make sure you set the nozzle pistol handle so it is open to the jet spray,) drop in tank. put bags in the bowl for blow back and cut on full blast and turn pipe to spray in all directions.....like I said it worked for me...............

step to take to prevent buildup to begin with
by: Theresa

read this at the rv.net website: each time we dump our blackwater tank (and verify it's clean with the clear plastic connection hooked up) we add about two squirts of dawn dishing washing liquid - and one or 2 quick flushes - this is supposed to slick the inside walls of the blackwater tank to prevent stuff from adhering (that and always use toilet paper for rv's) - haven't had any trouble with "stinky" tank since we started this practice....

gross job:(
by: El

i have a seasonal site that does pump outs.
This is my first time camping. I think it's gross. It's not getting cleaned out?? Unless I have it pumped. Don't use it for a week & keep a water- pine sol mixture in it? Run hose day before they pump out?

This doesnt work
by: Anonymous

There is a man on Utube that does a demo on putting ice in your tank .....look it up and watch it....we thought putting ice was a way to go but he convinced us that it just DOES NOT work.

Go to U tube and look up ice cubes for cleaning rv black tank and watch it........see for yourself!

clean tanks the easy way
by: Anonymous

1/3 to 2/3 full add couple bags of ice bigger chunks are better drive start and stop and winding bumpy roads to the dump station once in awhile fill from near empty up to near full do the drive the ice will scrape the sides very clean

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