The Best Way to Dump and Deep Clean Your RV's Sewer Tank

Updated on December 13, 2017
TIMETRAVELER2 profile image

I am an avid RV enthusiast who understands that my life and my safety depend on the condition of the equipment in my coach.

Knowing the best methods for cleaning and caring for your RV’s blackwater tank is important.

This job

  • is not hard to do,
  • takes relatively little time,
  • will keep your RV smelling good, and
  • will keep your plumbing system functioning properly.

The good news is that you won't even have to get your hands dirty if you follow the tips in this article.

Learn the best and most effective methods for dumping and deep cleaning your RV's blackwater tank.
Learn the best and most effective methods for dumping and deep cleaning your RV's blackwater tank. | Source

Step 1: Protect Yourself

What comes out of your sewer hose is toxic, so you need to protect yourself and your clothing by doing such things as wearing rubber gloves, shoe covers and protective glasses.

You should also keep some liquid soap and a roll of paper towels handy so that you can wash your hands, gloves and shoe coverings at an outside faucet after you finish the job and before you go back into your coach.

Step 2: Empty Your Tanks

To dump, you need to be parked beside a sewer outlet. This will either be located at your campsite or a dumping station.

  • If you are at a dump station, connect the sewer hose to your RV and then place its end into the sewer hole.
  • If you are at a full hookup campsite, your hose likely will already be connected to your sewer outlet.

When camping, always keep your waste water tank valve closed and your graywater valve opened.

However, before you dump, close the graywater valve, and allow it to partially fill with soapy water.

Do not wait to dump until your tanks are full of fluids because their weight can damage or break the tanks.


To dump, open the blackwater valve first. After the waste has gone out of the tank, fill the toilet with fresh water and dump the contents again.

Keep doing this until the water runs clear.

After doing this, open the graywater valve and allow the contents to empty into the sewer. This will help to clean the interior part of the sewer hose and keep matter from sticking to it.

  • If you plan to stay put, close the blackwater valve again and add a gallon of water and some Spic N Span to the tank.
  • If you plan to drive your coach, after dumping, close both valves, and place an enzyme cleaner along with about one gallon of water in the sewer tank.

As you drive, this mixture will

  • slosh around,
  • eat away at any hardened matter,
  • disinfect the tank and
  • help to eliminate clogs.

This will also eliminate odors that can permeate your coach and make it unbearable for living or travel.

Step 3: Deep Clean Your Sewer Tank

Most people think that regularly emptying tanks is enough to keep them clean, but this is not the case.

When using a coach either for travel or living, people need to dump every few days and also deep clean at least once each week.

To deep clean, you follow all of the steps listed above except that before you open the graywater valve, you also

  1. Drain the waste water tank completely.
  2. Fill it 3/4 full with fresh water and two cups of liquid bleach.
  3. Let the mixture sit for 10 minutes, but no longer.
  4. Drain the tank.
  5. Fill it again with 3/4 full with fresh water.
  6. Continue to drain and fill until you see that the clear hose connector shows no debris and the bleach smell has disappeared. This is very important to do because you need to make sure that there is no bleach left behind in your plumbing system. If there is, it can damage it.

Many people will advise you not to use bleach at all because doing so can damage your pipes and fittings, but I have used this method for more than 50 years and have never had a problem. The secret is to always mix it with a good amount of water and then eliminate it completely later.

Using Bleach not only cleans your tank, but also sanitizes it, which is very important for your health.

Following these steps, you then need to pressure wash the inside of your sewer tank.

Backwashing Equipment

Many RVs have built in backwash units, all of which do good jobs.

  • If your coach has one, your manufacturers maintenance books will show you how to use it
  • If not have one of these units, you need to buy a wand that is made especially for RV tank pressure cleaning.

There are several types, but my husband and I use the one made by Camco called the Flexible Swivel Stik because it swivels and has a manual shut off, which makes it much easier to use than other types of wands. It is inexpensive, easy to store and works great.

We've used this one for years and have found it much better than the more rigid types that don't have the shutoff valves because it eliminates the need to make pressure washing a two person job!

This is a must have item for people whose coaches do not have built in back wash systems. It stores well and always does a good job of ridding your tank of nasty residue.

Camco RV Flexible Swivel Stik with Shutoff Valve- Creates Powerful Cleaning Action that Dislodges and Flushes Stubborn Waste Deposits and Combats Odors (40074)
Camco RV Flexible Swivel Stik with Shutoff Valve- Creates Powerful Cleaning Action that Dislodges and Flushes Stubborn Waste Deposits and Combats Odors (40074)

This is a must have item for people whose coaches do not have built in back wash systems. It stores well and always does a good job of ridding your tank of nasty residue.


Backwashing Directions

You use both of these methods after dumping your sewer tank but before dumping your graywater tank.

The Built In System Directions:

To use your coach’s system, hook your hose to your RV and turn on the pressure washing valve located on your coach until the hose runs clear.

Then follow the rest of the directions noted above for dumping.

Directions for Using a Wand:

To use an RV tank cleaning want you

  1. attach a green garden hose to your campsites water spigot,
  2. connect the backwash wand to the hose,
  3. pull the wand and hose through a window or door and into your bathroom
  4. open the flapper of the toilet,
  5. put the wand down the opening,
  6. have someone standing outside turn the water on for you and
  7. keep moving the wand back and forth around the tank until you think all of the waste has been cleared.

With either method, you’d be wise to spend a few dollars to buy a clear sewer hose adapter because it allows you to see when the hose runoff is free of debris.

Using this gadget is the only way you can know that your tank is completely clean

Before we had our motor home, we used one that is made by Camco (can you tell that we like that brand?). It's inexpensive, durable and did what we needed for it to do.

Other brands also do a good job, but since Camco products have always served us well, we use them whenever possible

Walex TOI-11530 Bio-Pak Holding Tank Deodorizer - Pack of 10
Walex TOI-11530 Bio-Pak Holding Tank Deodorizer - Pack of 10

This enzyme product does an excellent job and will not harm the eco system.


Step 4: Using Enzyme Treatments

Once a tank has been dumped and deep-cleaned, it is a good idea to treat it immediately with a biologically friendly enzyme cleaner.

Depending on the size of your tank, you normally will dump every three to five days, so you don’t need to add this product every day, but never avoid doing this step because this is what will make future cleanings easier for you and will keep your tank odor free.

They are quite simple to use. Simply toss a packet into your tank and add one gallon of water as well.

Enzymes work to eat away the sludge that can accumulate on the sides and bottom of the tank. They soften it and turn it into liquid so that it can easily flow through your plumbing system and into a sewer.

If you don't use this type of product, clumps of hardened sludge can break off and clog your tank. When this happens, you can find yourself dealing with expensive problems.

Hardened waste items can lodge themselves in your pipes and valves and can be extremely difficult to eliminate. These types of issues can become so bad that repair people will have to take parts of your system apart to fix the problems.

Thus, it is much simpler to add these products following a dump.

Furthermore, they make tank cleaning much easier and faster.

There are many products on the market that can be used for this purpose, but I have found that using one such as the product manufactured by Walex that is environmentally friendly is simply the right thing to do.

These cost no more than others, but are equally effective and are just as easy to use.

For years now I have used the product I show below. I have had no problems whatsoever with clogs, and my tank never smells.

I used to use the liquid form, but the packets have proven just as effective and are much easier and cleaner to use.

Make sure to dump and deep clean your sewer tank prior to storing it.
Make sure to dump and deep clean your sewer tank prior to storing it. | Source

Storage Issues

Since many people only use their RVs for part of the year, it’s important that they deep clean their blackwater tanks before storing them.

Untreated or incorrectly treated sewer tanks that sit too long allow bacteria to build up and noxious odors to form.

By deep cleaning prior to storing, you avoid issues that can become problems and are guaranteeing that when you step back into your coach, it will smell good!

Good RV Sewer Care Is Important

Now that you know what you need to do to keep your waste water tank clean, sanitized and sweet smelling, all you have to do is follow the above guidelines.

Regular dumping and deep cleaning tasks are worth doing worthwhile because they will make using your recreational vehicle a pleasure!

How to Thoroughly Dump and Clean an RV Blackwater Tank

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Questions & Answers

© 2012 Sondra Rochelle


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  • TIMETRAVELER2 profile image

    Sondra Rochelle 10 months ago from USA

    You need to read the article again. You leave the gray tank open when you are parked at a campground and hooked up to a sewer, but in the morning, before breakfast, you close the gray tank so that you will have soapy water to use to clean out the hose through which waste matter goes to empty into the sewer connection. Your coach doesn't smell because you're confused. Your tank smells because you have not maintained it properly OR you have a clog. Dumping is not enough. At least once each week while you're using your RV you need to thoroughly backwash your tank until the contents run clear. Once you do that, you need to put a tank treatment and about a gallon of water into the tank. These treatments have enzymes in them that eat away at the waste and sludge and turn them to liquid so that you can avoid clogs. I would add here that you need to think about what you put in your Rv's toilet. You cannot use regular toilet paper. If that's what you've been doing, I would suspect a clog is your problem. I have an article about how to deal with clogs and you should read it.

  • profile image

    Terrielively 10 months ago

    This artical is contradicting. First video states leave gray tank open

    Second video states leave gray tank closed

    Well. Which is it. The odor in here is horrible and i came here for advice. Now I'm just as confused as ever.