How Long Can You Leave Black Water In RV? ( Emptying Holding Tanks)

How Long Can You Leave Black Water In RV

Have you ever wondered how long you can leave black water in RV?

While black water in an RV is hardly the most pleasant of things, it is a necessity if you have a toilet inside of your RV.

That waste has to go somewhere. Is it something that you should be emptying regularly, or can you leave it for a while? That is what we want to take a look at here!

How long you can leave black water in the RV? you need to empty and clean the RV black water tank every month otherwise it will start to smell. You can probably have it last a little bit longer if only urine is going inside of the black water tank.

How Long Can You Leave Black Water In An RV?

In theory, you can leave black water inside the RV for as long as you want. As long as that tank isn’t filled up, it is going to continue to accept waste.

The problem is that the longer you leave the black water inside of the RV, the more it will start to smell. This stench will probably be a lot worse if you are loading up the black water tank with solids.

While we are on the subject of solids, it would probably be amiss for us not to point out that, over time, any solids in the tank will start to harden.

This will apply even if there is a decent amount of liquid inside of the tank.

This means that if you are not cleaning the tank regularly, you are going to be left with residue at the bottom which is going to be ridiculously difficult to remove.

So, in summary, while you can leave black water in an RV for as long as you want.

However, eventually, it is going to start smelling. You will also find that at some point, it is going to be harder to clean.

In my opinion, you should be cleaning the black water out of your RV at every available opportunity.

Other than saving on the cost of a few chemicals, there is absolutely no reason to leave it there for long periods of time.

Read also: Is It Safe to Put Bleach in RV Black Tank? (Clean Black Tank in 4 Steps)

How Do You Prevent Black Water In An RV From Smelling?

Obviously, cleaning out the black water tank regularly is going to stop it from smelling. However, there are a few things that you will be able to do in order to keep those odors down to the absolute minimum.

In fact, if you follow these tips, you could use that black water tank for an incredibly long time without having to empty it.

You will still have the risk of solid waste sticking to the bottom of the tank, but these tips may even be able to prevent that.

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There needs to be an adequate amount of water in the tank

The water will help to prevent the waste from sticking to the tank and starting to harden.

It won’t stop it completely, but it may be able to help you go a small amount of time longer before you need to empty the black water.

The water will also help to mask any odors inside of the tank which, of course, will mean that there will be no stench that you have anyway.

It will only cover it for so long, but you should be able to go a short while without emptying the tank if you keep that tank filled up with water.

Read also: Does an RV Black Tank Have an Overflow?

Add chemicals often

If you have a black water tank, then you need to purchase black water tank chemicals. These will help to ensure that all of that waste is broken up inside.

It will also ensure that you can go longer without having to clean out the tank.

Although, once again, the chemicals will only be able to do so much to mask the smell. Eventually, no matter how many chemicals you end up adding to the tank, the smell will still be there!

You can add chemicals directly through the toilet. You will need to add them as per the instructions included with the chemicals as it can vary based upon the size of the tank that you have plus the number of chemicals that you are flushing into the tank.

Only flush organic waste and biodegradable paper

The only things going into that tank should be organic waste and biodegradable toilet paper, well, that and the water that you are flushing down too.

If you do not do this, then there is a risk of there being blockages in the system.

If blockages start to occur, then the smell will start to drift up from the black water tank and, trust us, this is not going to be a pleasant smell at all. 

If there is a blockage in the system, then make sure that you clean it out as soon as you can. This is a job that you can do yourself with some rather simple tools. 

Clean the inside of the black water tank

No. This is not going to be the most pleasant job in the world. However, every few emptyings of the tank, you will want to clean the inside of it properly.

Yes. There will be a bit of caked on residue, but with a decent abrasive pad (i.e. a normal cleaning scourer), you should be able to get rid of most of it.

Yes. This is going to be smelling quite bad.

Once you have cleaned everything properly i.e. loosened it from the tank, then you should flush the tank out with some fresh water.

WIth any luck, the inside of your black water tank should look almost ‘as good as new’. 

How Do You Clean The Black Water Tank In An RV?

How you clean the black water tank will be dependent on the RV and tank that you have. This means that we can only give you a rough guide on what you can do.

Remember, you should only be emptying that black tank into designated areas. If you have been using the tank properly, then it would have been loaded up with chemicals.

If you empty that into the middle of nowhere, then you are just going to be ruining the environment.

If you are on a campsite, then there will likely be a designated area to empty the black water tank.

In order to empty it, you will need to connect up a sewage house to the outlet of the tank. The opposite end up will need to be connected to the disposal area.

Open the valve and let it drain completely.

You can then move the sewage hose to the grey water tank and repeat the process with that.

This will help to flush out the sewage hose, plus you will need to clean the grey water tank regularly anyway.

Empty Your Holding Tank at Home >> Check out the video below:

How Many Gallons Does an RV Black Water Tank Hold?

how many gallons does an rv black water tank hold? The average size or capacity of black water RV tanks are between 18 and 64 gallons. Class B motorhomes have the smallest capacity starting at 10 gallons. The largest black tanks usually have fifth wheel with up to 88 gallons.

Should I Leave My Black Tank Open or Closed

Should I leave the black tank open or closed? The black tank valve should always be closed. If you leave the black tank valve open, the liquid will flow out.


How often you need to clean the black water tank will be dependent on your situation.

Some may need to do it once every couple of days, others one every week or so.

Do it as often as you can. If a stench starts to emit from the tank, then make sure that you flush out the tank as quickly as possible. That smell will only get worse otherwise. 

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Mike Gilmour

Hi, I'm Mike, co-founder, and editor of RV and Playa. My passion is traveling (with my RV) and enjoying the day at the beach (Playa)! Well, I originally created this blog as a way to share what I've learned by experimenting with the RV lifestyle, and I want to help others develop in life through new skills and opportunities.

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