Possible black tank vent issue

[flyingjack]

Good morning all; last week of 2+ months tour of SE US. Last stop; Savannah, rinsed black tank well before leaving (same as I've done for last year)= nearly filled up black tank (not all the way up to drain pipes in toilet) with tank sprayers and then drain. Ever since, it appears the black tank is NOT vented and burps when using. Still useable so probably won't start taking anything apart until I get home in a week or so.

Any suggestion or ideas?

Thanks for any input.

Jack

2022 Montana HC 295RL; FYI- always rinse well before leaving after using for any extended time, then add 1/4 tank or so and Dawn for travel to next stop= usually, an RV Park. Full bowl toilet flushes still do a better job than black tank rinse nozzles; but, easier to leave rinse nozzles on with a timer to fill tank.

[Marinerjoe]

Hi Jack (don’t greet like that in an airport),

We didn’t have the problem with our current Cougar, but our previous travel trailer had an issue with the black tank vent. As it was still under warranty we had the dealer diagnose and take care of it.

Our two problems were:
1. As the tank level increased, so did the aroma. And it was much worse when we ran the exhaust fan in the bathroom.
2. With the higher tank level, we also experienced a slight burp when flushing.

The problem was that the tank vent pipe went too far down into the tank. The aroma was because the top of the vent was below the roof line and the exhaust fan pulled the fumes into the bathroom. The burping was because the pipe, when below the level of the water, provided no venting.

The fix was to pull the pipe back up and secure it. A sh1tty job, and I was glad the dealer fixed it.

[NH_Bulldog]

If it has been working up until now and if you have been rinsing/flushing the tank like you said, you may have a blockage of the vent pipe, or the pipe has moved like Joe said.

A blockage could be at the end where it enters the tank. Rising “stuff” in the tank can clog up the vent pipe, then when you drain the tank, this “stuff” is left behind and has a chance to harden. The other possibility is that the roof vent is clogged with something.

In my opinion, the easiest way to diagnose both possibilities is to get on the roof, pop out the silicone plug from the screw hole, remove the screw and twist off the vent cap. At that point you may see an obstruction at the cap, or that the pipe has risen and was pressing against the cap or the pipe dropped down into the attic or if you shine a light down the pipe you might see a blockage down at the bottom.

Your next steps depend on what you find up there. If it’s a blockage, I would use caution with poking anything down there like a stick since you don’t want it to break in there or poke a hole in something and make matters worse. A water hose might work, just make sure your dump valve is open so you don’t pressurize the tank and get an eeuption out the vent into your face.

[JRTJH]

The easiest way to diagnose a clogged vent stack pipe is to just access the pipe from the roof, put a hose into the vent and "fill it with a couple gallons of water" or, just take a couple of one gallon milk jugs up on the roof and pour them down the vent pipe. If it's clogged, the water will stay in the pipe, if it's open then water will readily flow into the black tank.

If it is clogged, you might get lucky and the water poured into the pipe from on top of the trailer might just be heavy enough to push the clog back into the the black tank.

DO NOT POKE A SHARP OBJECT DOWN THE PIPE !!!!! Doing that is a "sure fire recipe for poking a hole in the bottom of the black tank and will "fix your problem" by causing you to need to completely replace the entire system from the bottom up.....

[flyingjack]

1st: thanks for you suggestions.
2nd: very sorry for wasting your time. My CRS (can't remember ****) struck again. Being old, fat and cripple has it's issues. Haven't traveling with another RV before and I was helping him on departure (distracted) and obviously didn't set my rinse water timer; therefore, I mostly filled the black tank again so it didn't take very long to get to totally full and the burping was indeed from being full=normal.
Carry on.
Leaving Paducah, KY area this AM wrapping up our 2 months touring SE US and headed for MO (in-laws) for couple days and then home to CO to fix/clean up 5er for next trip late May.
Again, sorry for wasting your time and crying wolf.
Jack

[NH_Bulldog]

If nothing else, the experience you shared may help others in a similar situation.

That being said, I would never let my tank flush run with the dump valve closed. As others here will attest, the results can be catastrophic, extremely messy and potentially very expensive to fix. You have provided a perfect example that mistakes can still happen despite taking precautions. I am glad you caught it before you experienced a volcano either out of the toilet or out of the roof vent (covering the roof and sides of the camper with “discharge”) or maybe worse, a ruptured waste tank.

[notanlines]

Filling the black or grey tank with the tank rinse on a timer is not a good idea. We read every day on this forum that bad ideas ‘work for me’ until they don’t.

[JRTJH]

We have had several different types of "water faucet timers" through the years. Electronic or manual, all of them have failed "sooner or later".... Typically, when they fail, it's when they can do the most damage in the least amount of time.

NEVER, (did I mention NEVER, EVER) trust any timer to protect a system (black tank storage system) when it is being filled with a pressure system after being altered (valve closed) from the original design for that use....

To do so is setting up your trailer for damage beyond your ability to repair with the ONLY benefit being a perceived convenience.....

In this case, it wasn't the timer that failed (all of mine have sooner or later) but it was the owner that failed (to remember what he was doing and got sidetracked).....

That's why EVERY trailer manufacturer puts that caution in their owner's manual... Do not use the black tank flush system with the terminal valve closed.....

You'll hear loads of people who will say, "But I'm not that stupid" or "I don't get distracted" or "My way has a foolproof timer, so the rules don't apply to my procedure" or "some other excuse"...

They will continue to argue that it's OK to do it, until the day they destroy their black tank system, and then they'll post things like I'm posting now....

All those "better ideas" do work...... UNTIL THEY DON'T ..... YMMV

[jimborokz]

I never used a timer since different parks have different pressure and flow rates. I have used a flow meter on the flush hose which tells you just how many gallons you have put in the tank. I never put more than about 10 gals. in the tank since once you fill above the sprayer in the tank it won't do any good anyway.

[Marinerjoe]

Originally Posted by jimborokz

I never used a timer since different parks have different pressure and flow rates. I have used a flow meter on the flush hose which tells you just how many gallons you have put in the tank. I never put more than about 10 gals. in the tank since once you fill above the sprayer in the tank it won't do any good anyway.

Jim, I likewise use a hose end flow meter. However, I go up to 20-25 gallons before I pull the dump. I’m not trying to have the spray hose clean the walls as it has limited effectiveness in my opinion. Rather, I fill the tank high in order to (hopefully) remove any paper from the sensors and to get a good rush and flush when the valve is opened.

I do this a couple of times to get the tank as clean as possible. And I do it in full hookup sites, not at a dump station (I don’t want to be THAT guy).