RV Black Tank Flush Check Valve Location (Pressure Regulator)

It is a guessing game. If you haven’t realized that by now, you may never find some parts in your RV or trailer. With the little room available, RV makers can get very creative and secretive with their parts’ locations. Your similar part may not be where your friends are in their RV.

There may be several locations for this essential part. For some RVs and trailers, the part may be located under the bathroom sink. Or it may be on a wall near the bathroom or across your unit on the other side from the dump valve.

To learn more about this location issue, just continue to read our article. It brings you the best news possible about this part and where it is. Just remember, different models and brands of RVs may have it in different locations than what is mentioned here.

RV Black Tank Flush Check Valve


The first thing to be aware of is the name of this important part. Some people say it is not called a check valve although many owners do just that. There are other names for this valve and they are anti-siphon valve, backflow preventer, or vacuum breaker.

You may not use those names, but it is important to be aware of them as other people will use them, especially in hardware stores or where these RV plumbing supplies are sold.

Once you are familiar with the names, the second thing you should know is that this valve comes in several different sizes and construction materials. The strongest and best valves are usually the brass ones. These are the ones you have to buy and install yourself.

The weakest and most fragile are the plastic options. These valves are the ones you find on most RVs and trailers. They have one factory setting and that is it. All these valves do is prevent any black water from coming back into your water supply system

They also should have a screen to keep any debris from doing the same thing. They are a one-way valve to let the water into the tank and rinse it out. The plastic ones can fail on you faster than the brass models.

But the plastic seems to be more expensive than the brass models so that is something to think about.

Do I Need a Pressure Regulator For Black Tank Flush?


Most RV owners do not have this part on their black water flush system. They usually leave the valve open so there is not any real pressure on the valve to worry about.

However, there can be a problem with these check valves leaking. At least one owner solved his leaking problem by adding this pressure regulator to his water line before the check valve.

Another owner ran into some super high pressure at one dump station and the pressure blew the hose off the threads. Since you never know what type of water pressure you will receive from outside sources, adding one may be a good idea.

But the choice is up to you and your situation. If you do not think you need one, then do not get it. It may not come in handy at all as one owner has not had a problem with high water pressure in 5 years.

You may never need it unless the part starts to leak. That is a big if as the part may not leak on you. But if you want to be safe and avoid this possibility, it is a good idea to install one.

The parts are not that expensive and may save you a bundle later on down the road.

Where is The Black Tank Flush Valve Located?


The essential location is 6 inches above the highest point of the feature it is attached to. What that means is if it is attached to your black water tank, this valve has to be 6 inches higher than the tank’s highest point.

This is a mandatory location and the instructions should say this as well. The non-essential and non-mandatory location is a different issue altogether. You may find this valve in a variety of different locations in your RV or trailer.

Some people find it under their bathroom sink, while others find it in the wall between the bathroom and another room. Or the washer and dryer room may have it as well. And it can be in none of those locations.

Where it is located may depend on the floor plan of your RV or trailer plus where the maker routed all the water lines. The location and position of the black water tank will also influence the location of the valves.

Your dealer may know and your owner’s manual may have a diagram of where this part is located. Suffice it to say, that you may have to play a guessing game before finally finding it.

Once you do find it, it is guaranteed you won’t forget where it is.

What Does an RV Vacuum Breaker Check Valve Do?


The role this valve plays is a very important one. It is designed to prevent any black water from going up your water line and contaminating the rest of your water supply.

This is a one-way valve that lets clean water through in the direction of the black water tank. That clean water is used by your tank flushing system to clean out the tank after you have dumped the main contents.

Then it blocks any residue, splashes, and debris from finding their way back through that water line and mixing with your potable water. It is a necessary device if you want to protect your health and water supply.

Unfortunately, these valves can leak or break and you may find a nice puddle of fresh, clean water on your floors. You just need to clean up the water and replace the valve.

In some cases, all you need to do is put a water pressure regulator on the line and that helps stop the leaking.

RV Black Tank Flush Check Valve Leaking


Once you start using this flush system, you may see some dripping coming from the check valve. This is normal if the drops are coming very slowly and far in between.

If you see a large puddle on your floors, then you know there is a problem with this valve. You will have to find its location and check to see if it came loose or not. The plastic models are prone to failure and famous for not lasting a long time.

The only real repair you can do for the plastic models is to replace them. If you see a lot of water even after you replaced the valve, then it is possible the water pressure coming into the valve is too low.

Too low of water pressure means that the seals do not sit right and the leak takes place. The other repair you can do on this valve is adjust the water pressure so it is at or above the manufacturer’s recommendations.

If the valve is stuck either in the open or closed position, then you have to replace the valve. Once you made the right repair, you should not see a lot on your floor.

No Built-in Black Tank Flush System


There are some RVs and trailers that do not come with this system. That means you do not have to worry about anything that has been said in this article. Unless you decide to install one on your own.

Then you will need to know all about this important valve and how it works. There are some good after-market flush systems you can buy and install. Most of the systems you can buy will require that you drill a hole in your black water tank.

Just drill in the right location. These systems are not that expensive, depending on where you make your purchase. They can be found for less than $40 on Amazon.

However, if you do not want this type of system, you can go with the flush wand instead. No installation is required. That makes it easy to buy and use. Both systems do not have a set time limit for flushing.

You should flush until the water runs clear. To see this change in the water, you may have to install a clear elbow that lets you watch the water exiting the black water tank.

Not a pretty sight but it has to be done.

Some Final Words

Finding your black water tank’s flush check valve may take some time. It could be anywhere in your RV or trailer. The first place to look, though, will be under your bathroom sink. That is the most logical place it would be located.

If it is not there check your laundry room, kitchen sink, and bathroom walls. If you have this system in your RV, it will be somewhere. Plus, it will be 6 inches above the highest point on your black water tank.

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