Black Tank Odor Question

[dankirk]

We purchased our Windjammer 2 years ago. We had a Wilderness trailer for 9 years before. We’ve always used Happy Camper tank treatment and never had odor in the Wilderness. In the Windjammer, the bathroom starts smelling when the black tank gets full. The odor goes away after dumping.

I assume the odor is coming through the roof vent, which is close to the black tank vent on the roof. Why would it only smell when it’s full? I assume that odors are always escaping the blank tank vent, full or not. Also, shouldn’t the bathroom’s vent fan push the odor out and prevent it from entering through the vent?

Not a huge problem, but just don’t know why it stinks when it’s full.

[TitanMike]

When full more "stuff" decomposing causing stink.

I'd check the roof vent to make sure it's really clear. Could also be that vent is extended too far into tank and when full it's closed off with the "stuff" in your tank which leaves the flush valve as the only outlet for gases causing the odor.

Could be also time to explore a different tank chemical. I use Odorlos and find it works (at least for me) better than any of the numerous other chemicals I've used over the last 40+ years.

As for determining whether or not the vent is extended too far into the tank, it may be necessary to have someone look inside with a flexible "borescope" after you've dumped and rinsed well.

If it's a matter of odor coming through the roof vent, sometimes a vent cap that swivels in the wind and only discharges odor downwind helps. Discharging in the direction the breeze is blowing will help disperse the odor more quickly.

Back to chemicals. Some just try to mask the odor with a strong scent. Others work to keep the breakdown to a minimum so more odors aren't released. Some even try to help the "sewage" break down more quickly and also mask the new odor with their own fragrance. Big thing is to make sure you have good vent flow.

[bsinc1962]

One thought on this as I've experienced something similar on my GeoPro. If running the vent fan with all the windows and door closed the draw on the exhaust fan is so strong that the only place to draw air in from is through the sink drain or shower drain. As soon as I open a window slightly the pitch of the fan changes and the odor goes away. The camper is that air tight. I'm not sure why the trap in the drains aren't blocking this but this is what I've observed.

[Ebills4595]

Originally Posted by bsinc1962

One thought on this as I've experienced something similar on my GeoPro. If running the vent fan with all the windows and door closed the draw on the exhaust fan is so strong that the only place to draw air in from is through the sink drain or shower drain. As soon as I open a window slightly the pitch of the fan changes and the odor goes away. The camper is that air tight. I'm not sure why the trap in the drains aren't blocking this but this is what I've observed.

We just remedied a similar issue with our 2504S. We were smelling not so pleasant odor from the AC vent closest to the exhaust fan in the bathroom. After checking everything the determination was that the fan was sucking the black tank smells back into the roof cavity from the top of the black tank vent.

When I removed the vent cover I found that the hole the vent pipe travels through the roof is not sealed and there is a good sized gap around it. The stock vent cover also does not connect to the top of the vent pipe, it simply sits on top and covers it so I can see how with the right pressure gas could get sucked into the roof cavity from the pipe.

I replaced the vent covers with the ones that pivot with the wind (they also connect directly to the vent pipe vs. just covering it) and also sealed around the pipe where it exits the roof. That has solved the issue for us.

[myredracer]

Some have reported their vent pipe has slipped down into their black tank. That *might* explain why you get odors only when the tank is full. Sorry, but not sure how to test if it has only partially slipped down.

Maybe get on the roof when the tank is full and blow hard on the vent pipe and see if it gurgles!?

[Flybob]

As mentioned above, the vent pipe may extend too far down in the tank either from slipping or assembled like that originally. Once the liquid gets above the vent, you no longer have a working vent.

[bedubya]

My cousin swears by this:
https://www.amazon.com/Lippert-Compo...74999996&psc=1
But I removed the cap (2 screws under a lot of caulking) and discovered the vent pipe stuck too far up. I cut it flush with the vent and it was much better.