Should I leave my black tank open or closed?

In this blog post, we will answer the following question: Should I leave my black tank open or closed? We will discuss what can happen if you leave the black tank open and how to properly maintain, empty and clean it.

Should I leave my black tank open or closed?

Whenever leaving the campground, you should make sure that the black tank is tightly closed. When you flush the toilet, the black water goes into a reservoir. If the drain valves are closed, the black water remains stored in these tanks. Obviously, if you do not want to lose the contents of your tanks along the road, there must be a system that closes them. And there is one: the shut-off valves.

Shut-off valves are placed at the outlet of each tank. They look like a cage since the blade that performs the shut-off is embedded within a watertight cage. This cage not only waterproofs the tanks but also gives them greater structural rigidity. Cages allow you to never touch any part that has been in direct contact with the waste.

It is highly recommended to open the valves one at a time and completely. Try not to leave your shut-off valve half-open while discharging, slowing down the drain only serves to leave more waste in the tank. 

What happens if I leave the black tank open?

You do not want to leave the black tank open while on the road. In this case, all the residues and liquids will accumulate on the bottom of a holding tank. You will find yourself with a pile of faeces at the bottom of the black holding tank. No, who wants to deal with that? 

We don’t talk much about it, but black water can become a real nightmare. This is, consequently, a delicate but very important subject. 

You should know that the toilets onboard RVare devices for disintegrating and evacuating wastewater. Everyone will tell you when it comes to the toilet, prevention is better than cure! With this in mind, we advise you to follow a few rules of good use.

First of all, you have to be extremely careful what you throw in it. Only suitable toilet paper is accepted. Next, you have to clean the toilets with specialized, organic cleaning products. Products containing acetone, trichloroethylene, and any product that could damage rubber parts should be avoided.

How does the black tank of an RV function?

For regular circuit maintenance, it is important to understand the mechanism of the blank tank.

You should know that there are two types of toilets:

  • Manual toilets: you have to pump to start the suction of black water.
  • Electric toilets: buttons are enough to activate the entry of freshwater into the basin and the suction of black water.

There are therefore two ways of emptying your toilets: either having them emptied in designated places in RV park or discharging this black water on the ground (in authorised places along the road).

A few tips to avoid RV black tank “accidents”

  • To avoid the oxidation of the valves connected to the toilets, it is essential to handle them (they are hidden under your floor) about once a month, by opening and closing them.
  • If you are in an area where the discharge of black water is authorized: rinse the tank as regularly as possible, this amounts to opening the valves, filling the tank with fresh water and drain it through the through-hulls. 
  • Also, be sure to empty the black water tank when you are in an area where temperatures are negative to prevent freezing in the pipes. It is not recommended to use anti-freeze, for compatibility with the circuit.
  • Finally, the most important thing is to empty the black water tank before leaving your RV. Remember to drain it with fresh water (never with seawater) to leave only clear water in your circuit. Otherwise, the black water will dry up, clog your pipes, damage your tanks and spread bad odours in your RV.

If the toilet ends up getting clogged anyway, there can be several reasons: either something is blocking the operation of the grinder, or your manual pump is blocked, or your through-hull is clogged.

If you wish to carry out the repairs yourself, certain precautions must be taken, such as shutting off all the valves of the toilets concerned and shutting off the water circuit in order to repair safely.

You can disassemble the grinder and possibly its motor to remove the blocking element. If you have a manual toilet, you can take the pump apart.

How to empty the black water tank of your RV?

Those who have sewage tanks, just pull a lever to open the lock valves and release their contents. There are those who have a remote control to perform this procedure from the inside and without having to get out of the vehicle.

On the other hand, if you have a chemical toilet, once you take the tank out of the bathroom for flushing, you must move the container tightly closed. If you are going to go to a public restroom or a service station, I recommend that it be at a low time, since the smell can be unbearable during the discharge. 

Lift the toilet seat. Have a container of water on hand for the first and second rinses. Remove the lid carefully and dump the remains trying to splash as little as possible, because the disintegrant is caustic, although I think this would be the least of the problems. Some have an angled weir and a valve that is depressed to let air in and debris doesn’t spurt out.

How to clean the black water tank?

I recommend that you do this procedure once the trip is over, before storing the vehicle and with the sewage tank empty.

Step 1: With the sewage tank empty and the shut-off valve closed, flush 1 cup of floor disinfectant liquid, 1 cup of baking soda, and a 5kg bag of ice through the toilet.

Step 2: Start the vehicle. The movement of the ice against the internal sides of the tank works as a brush that, complemented with the baking soda, will make it easier for the accumulated solids to come off. The disinfecting liquid for floors will leave you disinfected and smelling of perfume.


The conclusion is quite simple: as long as you are at a campsite, you can keep the RV’s black tank open. This way you will be able to enjoy long showers and you will be able to flush the toilet whenever you want without too many worries.

Once you leave the campsite, it would be good to close the black tank well, so as not to scatter the debris everywhere or to risk damaging the holding black tank.

If you have further questions, comments or tips on the content, please let us know!

FAQ on Should I leave my black tank open or closed?

What is the procedure to treat sewage?

Wastewater treatment begins with the physical separation of large solids (garbage) from their current, using a system of grids (meshes), although such wastes can also be crushed by special equipment; subsequently, a grit is applied (separation of solids)

How to clean the clean water tank of an RV?

To clean the clean water tank of an RV, follow this guideline: to each litre of water, you must add 2 drops of 5% chlorine. If you do, your water will be much more drinkable and clean, eliminating the risk of acquiring different diseases. At we have many years of experience renting and improving your caravan.

Where to dump the sewage?

The sewage is poured directly into an aseptic tank or cassette. The tanks or cassettes that collect the sewage have a rotating tube through which they are discharged into the corresponding drain, and which must be connected to an aseptic pit or the sewer.


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