Black tank flush flooding bathroom

[Javin]

I have a 16XRB and to my surprise while doing the usual black tank flush by connecting a hose to the flush valve I noticed water coming onto the floor in the bathroom from where the floor and wall meet. I took a look under the sink and water seems to be coming in from somewhere while flushing the tank. It also seemed to be getting wet on the floor beside the shower and toilet as well. Also the water from the hose seems to be spraying out and not going into the flush valve like it normally does. I’m guessing a blockage and or leak?
Has anyone else had this problem? Time for a service call I guess. Figures this happened just after my extended warranty ran out.

[2edgesword]

As far as I know the black tank flush goes directly into the black tank so I'm not sure how water is getting from the hose to anywhere else in the trailer.

Are you doing the flush with the dump valve open?

[TWP723]

Are you sure the tank is empty? Have you used the flush before? The gate could be stuck closed, filling the tank and overflowing. Get a flash light and have someone turn on the water.

[Javin]

Yes tank has been emptied out and dump Valve was open. I have been using the tank flush valve after every trip for years and never had a problem. Maybe the hose located directly behind the valve has a leak or is blocked? I find it odd that water does not seem to be going through completely like it used to and is spraying outside the trailer.

[craigav]

It is common that there is a check valve vacuum breaker installed in the flush line. Sometimes they go bad and leak when flushing the black tank and need to be cleaned, repaired, or replaced.

Here is an example, however most I have seen are black and have a square head, but this one says it will replace the older design.

These are located along the flush line, which is commonly in the wall behind the bathroom wall, but generally right behind a foot or two where you connect your flush hose.

https://www.etrailer.com/Accessories.../A10-3050.html

~CA

[craigav]

Here is what I was referencing and at a lower cost, I am sure the etrailer one would work but cost 3x more.

https://www.ebay.com/itm/28380212235...46417e3acb64c8

[DrSmart]

The black tank flush has a check valve (back flow preventer). Ours is in the wall behind the shower taps. There's a removable access panel on ours. Our previous trailer had the check valve under the vanity sink. There are two screw on fittings for input and output on the check valve. Ours has gotten loose before and allowed leakage. Just needed tightening.

[Javin]

Thanks for these suggestions. After reading the reviews for the check valve link it sounds like this is the problem. Many ppl mentioned the exact same thing with the bathroom flooding while flushing the tank.
Not sure if it needs a replacement or is just loose at this point and I’m not too handy with plumbing issues. Does anyone know how to access this check valve in a 16XRB? I will check for access points mentioned. If it’s loose I can handle that. Just not sure where it would be.
Cheers

[craigav]

Originally Posted by Javin

Thanks for these suggestions. After reading the reviews for the check valve link it sounds like this is the problem. Many ppl mentioned the exact same thing with the bathroom flooding while flushing the tank.
Not sure if it needs a replacement or is just loose at this point and I’m not too handy with plumbing issues. Does anyone know how to access this check valve in a 16XRB? I will check for access points mentioned. If it’s loose I can handle that. Just not sure where it would be.
Cheers

If you can locate it, it is not challenging to replace it (if needed) as it connects inline just like attaching the water hose to your RV's water inlet. ~CA

[ultrarider]

I have a 2018 16Xrb. That backflow valve is under the bathroom sink. Remove the bottom panel in your cabinet. You can’t miss it. Mine is black

[Javin]

I found the area under the sink and tightened the connection. When I turn the water on I can see water running down the back wall circled in the picture. I am guessing there is a blockage in the check valve sending the water back out? The leak is before the check valve for sure. Could it be the inlet for the black water flush?

[ultrarider]

My thought would be to disconnect the backflow valve (remove it) Then use a compressor at low psi to see if you can blow into the tank from where the backflow valve was removed. Then blow the line from outside. Chances are that valve is the culprit. I would replace it regardless.
JMO

[Arnold R]

I had some leakage under that sink last year. I later realized that the hose was connected to the faucet directly, without a pressure regulator. This year I inserted the regulator and didn't have any leakage.

I wonder whether the backflow valve leaks when the water pressure is too high.

[Javin]

An rv service person told me some ppl just replace these with a basic elbow connection. I know having a back flow protector is the purpose of this part but I’m wondering how common back flow would actually be and if this part also stops black tank odour. Anyone swapped theirs out before?

[Javin]

Wow, after changing out the breaker check valve the problem still persists! At this point I’m not sure what to do. I thought for sure this would work but unfortunately it did not. Could there be a blockage in the line perhaps? Water is spraying out of the black tank flush inlet.

[Javin]

So after removing the pipe connected to the black tank flush inlet I can see there is nothing blocking the inlet and the pipe is clear as water runs through it. I’m sure the problem is beyond the check valve now. Strangely I noticed the black tank reading 2/3 full even though it was just emptied at our last trip and not used. Then when I looked in toilet I can see standing there water quite high up. It seems as if something is suddenly blocking the toilet drain as I’m sure it used to be a clear drop and now I can’t even see down it. I tried poking a long stick down there and it seems completely blocked by something hard. Anyone know what could be happening here? I’m puzzled.

[Javin]

This seems to be a toilet/black tank issue so I have started a new thread. Thanks to everyone who chimed in and provided helpful feedback.

[JimmyP1962]

I had a similar problem with the fresh water leaking into a storage area where the inlet connected to the water line. Over time, because of how I was disconnected it, it came loose and caused the leak. My black tank flush was right next to it and was a little loose. I tightened both of the lines from the inlet and have not had a problem since, however I do check it from time to time. Good luck!

[robert9999]

Jayhoozit Cripes. These damn RV manufacturers should be sued to death. Water on your floors, to me, is the end of that unit's integrity, mushy floors will appear eventually. Those Luan floors are about a 1/8th inch thick. Now if you sell it & don't disclose the flood you are in trouble also, just sick of hearing these issues due to manufacturers low quality.

[Johnynorthland]

Originally Posted by craigav

It is common that there is a check valve vacuum breaker installed in the flush line. Sometimes they go bad and leak when flushing the black tank and need to be cleaned, repaired, or replaced.

Here is an example, however most I have seen are black and have a square head, but this one says it will replace the older design.

These are located along the flush line, which is commonly in the wall behind the bathroom wall, but generally right behind a foot or two where you connect your flush hose.

https://www.etrailer.com/Accessories.../A10-3050.html

~CA

X2 my check valve leaked on my first RV!