Black Tank Venting Issue

[Phydeauxman]

I have a 2015 Reflection 323BHS that we purchased new in 2014. We have had an issue with the black tank venting properly ever since it was new...but being newbies (this was our first and only camper), we did not realize it till much later. Ever since new, when flushing our toilet we get 2 behaviors that appear to not be normal; 1) the smell that wafts up thru the toilet and 2) a burp of air that pushes the water up before letting it pass down into the holding tank. To date, we have just been living with it (we are not full timers) but I really would like to get to the bottom of the issue and fix it. I have looked at numerous videos on YouTube trying to find an in-depth discussion on the components and structure of the black tank. I would really like to have a grasp on how the system as a whole is designed and put together before I start tearing into it to figure out what might be causing the problem.

A motivator for putting some attention on this now is that the gate valve for the black tank is getting harder and harder to open and close so I suspect I am going to be addressing that soon. Would like to take care of both issues once I open up the belly.

I would be eternally grateful to anyone that can help me diagnose and repair the problem.

[Riverbug]

Not a fun issue. Here's what I've experienced in the past with an older trailer...the vent stack (black pipe that goes up through the roof) was not properly secured when installed. It actually "slithered" down over the years so that the bottom of the pipe was actually in the water within the black tank once the tank was about half full or so. This caused two issues: 1. the burp and 2. the pressure built up in the tank at times made it difficult to slide the gate valve.

The bottom of the vent stack should be adhered in place at the top of the black tank and not protruding down into it (or at most only slightly). My suggestion would be to flush the tank very well and empty it. Get yourself an endoscope with a flexible wire that holds shape so you can view inside the tank and see if the vent pipe appears to be ok or not. That's where I would start.

I can't tell you how many times this thing has come in handy for looking in tight spaces...https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Hope that helps.

[Rabbit]

Previous recommendation is spot on IMO.

[Riverbug]

@Phydeauxman forgive me, I previously jumped to the cause of my past experience. But there is a simpler and easier first step to check. It popped into my brain at 04:30; you're welcome.

Go onto the roof with a bright flashlight. Locate the vent stack. Assuming there is a cover over the pipe see how it is sitting. Is there a gap between the top of the pipe and the cover to allow airflow? The covers used to be held in place by metal spring clips that hold tight to the inside of the ABS pipe. (I haven't looked at my new one so not sure if they are still secured that way.) Remove the cover and peer down into the stack with your flashlight. Is there anything blocking the pipe? Is there any obvious problem that you can see that would restrict venting?

If you get an endoscope long enough you may also angle the camera up and drop it down the stack to see how the pipe is sitting in the tank (as previously suggested). Otherwise, going back to the first suggestion, I didn't mention it may be easiest to send the camera down through your toilet rather than through the dump valve, depending on your layout. The stack typically is going to be located near the toilet but I suppose not always the case.

Good luck! Please let us know how things turn out and share your findings. This is a great forum for everyone to learn from.

[WhittleBurner]

​You have gotten great advice, I just want to add that the vent pipe sometimes slips and goes to deep into the tank. Follow the suggestions above to find it. Is the burping all the time or just after a while of use ?

[Phydeauxman]

All great advice...thanks for taking the time to reply. I was thinking the pipe being to far down in the tank might be the problem but since I cannot see the tank, had no idea how the pipe was actually connected to the black tank. I have ordered and endoscope and once it arrives, I plan to go up on the roof and snake it down the vent stack to see what I see.

[Rabbit]

Once you remove the roof cap, it may be obvious the pipe has slipped down if the end of the pipe is far below the cap. On mine, the top end of the pipe is just below the cap. Also, my caps are held by plastic posts that fit tightly into mating holes in the base that’s mounted to the roof. Cap just pries off.