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How to Dump, Clean and Protect Your RV's Blackwater Tank

Updated on July 24, 2017
TIMETRAVELER2 profile image

I am an avid RV enthusiast who has traveled, lived, workcamped and volunteered nationwide for more than 50 years and am still going strong!

If your motor home or camper is full of noxious odors or your toilet clogs up regularly, you can generally eliminate these problems completely by using the best methods for dumping, cleaning and protecting your blackwater tank.

This job

  • is not hard to do,
  • takes relatively little time,
  • will keep your travel unit 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 as well as those provided in How to Get Rid of RV Toilet Smell in Three Easy Steps.

How to Care for Your RV's Sewer Tank

Directions for properly cleaning and maintaining the blackwater tank in your RV.
Directions for properly cleaning and maintaining the blackwater tank in your RV. | Source

Always Wear Protective Clothing

Before you start cleaning, make sure that you are wearing old clothes, rubber boots or shoe covers and rubber or latex gloves that will not tear.

What comes out of your hose is very toxic, so you do not want any of the mess to get on your hands or clothing.

Also, make sure to 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.

You do not want to track any of the mess back into your RV!

Dumping Is Just the First Step

Most people think that regular dumping will keep a tank clean, but it won't.

Furthermore, knowing how and when to dump really matters. When using your coach:

  • Keep your waste water tank closed and your gray water opened.
  • Before dumping, close the gray water tank and allow it to partially fill.
  • Empty the sewer first and the gray water second. (By doing this, you clean the matter off of the hose and keep it from clogging.)

Do not wait until tanks are full because this puts too much weight on them and can cause breakage.

After dumping, place an enzyme cleaner along with about one gallon of water in the blackwater vessel. As you drive, this mixture will slosh around and eat away at any hardened matter.

This will keep it from sticking to the sides and causing clogs. It will also eliminate odors that can permeate your coach and make it unbearable for living or travel.

Directions for Basic Cleaning

Many RVs have their own back wash systems, but some do not.

Either way, you need to pressure wash your tank after dumping in order to clean it effectively.

To do this, either use your system or a special tool made for this purpose.

  1. Back washing is much easier if your coach has its own system.
  2. Using the tool is equally effective but can be awkward, messy and time consuming because to do so entails running a hose through a window and having one person control the water while the other does the pressure cleaning.

If for some reason you don't have time to use either method, a good alternative is to fill the tank 3/4 with fresh water, dump and then keep filling and dumping until the water runs clear.

Using a clear sewer connection will allow you to visually see that the water from your sewer tank is running clear and no more debris is exiting.

If you are unable to do a back wash or really do not want to do so due to time constraints or other issues, you can wait to until you do a deep cleaning to take care of this job. However, make sure you don't wait too long.

Waiting more than a week when you have not been pressure cleaning along the way can and will create serious problems for you, bring noxious odors into your RV and make deep cleaning much more time consuming and difficult.

After every cleaning you should make sure your tank is as empty as possible and then put an Enzyme treatment and a gallon of fresh water into the tank.

Enzyme treatments come either in liquid or packet form. The packets are much easier to use because they are pre-measured and come in easy store containers. I have used both and have found the packets to be the most convenient.

This mixture will slosh around while you are driving and will help to loosen and disintegrate some of the remaining hardened residue which will then flow out of the tank the next time you dump.

Directions for Deep Cleaning

If you back wash regularly, you will only have to deep clean every few weeks. You should also do so prior to and following each RV trip.

In the first instance, doing so refreshes your tank and rids it of old odors. In the second, you are preparing your tank to sit in storage for long periods of time and are keeping any hardened residues from forming.

Untreated tanks that sit too long allow bacteria to build up. This translates to noxious odors that can permeate an RV and make it uncomfortable for travelers. By taking these simple steps to prep your coach either for storage or travel, you are avoiding issues that can become problems and guaranteeing that when you step back into it, it will smell good!

Here are the directions for doing a deep cleaning:

As stated above, you will need to either use your built in pressure cleaning system or a special wand like the one shown below after you have deep cleaned your tank. (I used it for years prior to buying a coach that had a built in backwash system because, although there are other types, this one was efficient, easy to use and stored well.)

  1. Drain the waste water completely.
  2. Fill the tank 3/4 full with water and add two cups of liquid bleach.
  3. Let it sit for 10 minutes.
  4. Drain.
  5. Fill 3/4 full with fresh water.
  6. Continue to drain and fill with fresh water until you see that the clear hose connector shows no debris.
  7. Sometimes you have to perform this entire process a second time. If so, be sure to fill and drain thoroughly with fresh water. This is very important to do because you need to make sure that there is no bleach left behind in your plumbing!

Never use the liquid bleach in your tank for more than ten minutes when it is mixed with water, and never use it full strength because doing these things will cause damage to your plumbing system.

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.

Camco 40074 Flexible Swivel Stik with Shutoff Valve
Camco 40074 Flexible Swivel Stik with Shutoff Valve

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.


Using Enzyme Treatments

As stated above, once a tank has been dumped and 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.

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 and difficult problems.

They 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 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.

Walex BIO-11530 Bio-Pak Natural Holding Tank Deodorizer and Waste Digester, (Pack of 10)
Walex BIO-11530 Bio-Pak Natural Holding Tank Deodorizer and Waste Digester, (Pack of 10)

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


Take Care of Your RV's Blackwater Tank!

Proper RV sewer tank dumping, cleaning and maintenance may seem complicated, but it is not that difficult.

It just takes some time, the right tools and products, some effort and a willingness to learn.

The bottom line is to understand how important it is to care for your RV's blackwater Tank. It can make a huge difference in savings and comfort and will make your vacations much more pleasant.

How to Thoroughly Dump and Clean an RV Blackwater Tank

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  • TIMETRAVELER2 profile image

    TIMETRAVELER2 4 months ago

    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 4 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.