black tank smell-tried everything

[klmurphy]

Our 2010 Cardinal has had issues of black tank odors from day 1. The dealer claims to have "checked it". We've been RVing for over 10 years and don't feel completely ignorant on the subject however here is the problem...it doesn't matter if the temperature is 30 degrees or 90 degrees and how little or much toilet treatment you use (or what brand for that matter) when the black tank reaches approximately 20 gallons (full is 40 gallons) the odor is extremely noticable. We do not get any "splashback" when flushing and when we drain the black tank, there is a good flow. Although this issue has ensured that we have never overfilled our 25 gallon portable blue goose, we know it's not working correctly either. Any suggestions? Appreciate comments & help!

[OldCoot]

Would check the roof vents by pulling the caps off and inserting a garden hose in them (without the water being on in the hose in case there is a blockage)

[3 Happy Campers]

An RV holding tank is no different than a septic tank for a house. There is a complete biological universe in the tank.
A properly functioning system will have little or no noticeable odor. Using nasty chemicals to clean or help break down those solids kills the ecosystem & only masks the odor for a short time.

We have been using organic “EarthwormSeptic System Treatment” powder for a couple years now & do not have any odor at all.
After dumping the tank I add a couple gallons of water to help keep the ecosystem going & that’s about it. We throw in a ¼ cup or so a couple times a year as a booster.


Earthworm Family-Safe Products

[Twisty]

I haven't used the GEO Method yet, but I'm sure that it works.
https://sites.google.com/site/cbruni/

Edit: After reading Douglas' post below, I think that he is onto something. I was looking at tanks on websites and it seems that they are not pre-drilled for vent pipes. If the RV manuf. drills the hole and installs the vent pipe...
Your install may have been a Monday morning hangover job. LOL

[Douglasdh62]

It almost sounds like the vent pipe is too far down into the holding tank, especially since it doesnt start until you have about 20 gallons in the tank.
I dont know how to check that out, one way might be to take a tape measure and try to measure down from the roof to the bottom of the tank and then try to catch the edge of the pipe with the hook on the tape to see what the difference is. then you would need to know about how tall your tank is and then compare the 2 numbers the vent pipe probably should not stick down into the tank any further than and inch or so.

[TURBS]

Is the smell when you flush after half full ?
I think what could be happening is that when your tank gets half full your vent pipe is covered up because it sticks to far into tank and the smell cannot go out vent .
its possible

[Bill m]

The most logical problem is a blocked vent pipe, remove the cap and check it out. I have been advised never to treat the holding system in an Rv as a septic system - two differing animals. Ours is just that a holding system.

[3 Happy Campers]

IMHO the author of the GEO article must have been huffing too much beach fumes & it sanitized his brain. A proper working vent & a proper functioning biosystem system equals no smell.

Also he mentions in the article to only use “RV TP”.
Don’t waste your money on special “RV TP” unless you like throwing your money down the drain too. We’ve been using Scott single ply for over 20 yrs & have never had a problem.

[JohnandPandra]

For what it's worth, we had trouble with our black tank smell soon after our purchase of our TT, and I installed the Cyclone Vent on the roof. Very easy installation and no more smell. In later camping trips, we encountered grey tank smells emerging, and I installed another on the grey tank vent. Took care of that too. No more since and its been 3 years.

[Fire Instructor]

If it gets more noticable at a partially full level, it sounds like the vent pipe is inserted too far.

Something else to check would be sink and shower traps. Sometimes, due to floorplans, a sink (or worse - a shower) will be routed into black instead of gray tank. If this happens, and the trap is dry (some people never use a second sink, and I know some who use their shower as a closet or pantry, and bathe in the CG facilities), then this dry trap will allow fumes to pass. Water poured down the drain will fill the trap, and stop fumes.

[jimh]

as already mentioned. especially if u bought new and the problem is from day one, i would suspect either the main line from the comode or the vent extending into the tank too far.
i don't really know abt either, but i believe the 4" goes thur a seal into the tank. the vent may do the same.

mine started smelling when almost full. never did that before. the floor also started saging under the comode...ie the pipe would be driven deeper into the tank.

[dimurrrw]

The effluent rises, the dropped vent is blocked. Oh my, it now smells soooo good when the pressure rises and you crack the seal. Also, turn off that fantastic fan if you have it on.

[Herk7769]

Originally Posted by dimurrrw

turn off that fantastic fan if you have it on.

Yep, that was going to be my input but you beat me to it.
When the tank starts to "ripen" odors normally go up the stack. The vent fan can actually pull those vapors right back into an open roof vent and into the camper. A breeze from the wrong direction can do the same thing.

Gray tank stink smells an awful lot like black tank stink sometimes (especially if you dry camp a lot. Food bits and grease get into the tank and make for a lovely smell.)

I found that when I dry camp we don't use the shower. Started getting smells in the bathroom after a month in the hot sun in Key West. Turned out they were coming from the shower drain. Water had sloshed out of the drain while driving and the remained evaporated over a few short days. Tank smells came right up and into the camper.

[crocus]

"An RV holding tank is no different than a septic tank for a house."
================================================== =====
You obviously have never had a house septic system, as an RV tank is nothing like that.
Maybe the OP needs to change his diet?
Seriously though, there has to be some kind of venting issue, as the vast majority of RV owners don't experience this problem.

[dezolen]

check the vents under the sinks. Replaced mine twice already due to poor seals. Smell comes from gray water tanks and it sure does stink.

[Herk7769]

I have to add my .02 here.

In my honest opinion, an RV holding tank is NOT a septic system and should not be treated as such. It is designed to hold waste until you can dispose of it. It is not designed to "digest" that waste into a liquid (NORMALLY) so it can be spread into a drain field.

Keeping that tank as clean and slippery as you can will make sure you get all that stuff out in one good flush.

I use Calgon and laundry soap after every dump when dry camping and when in hookups the same with an added Turbo Flush till clear.
Once a year before I put it up for the season it gets a 48 hour RV-Digest-It treatment and a Turbo flush.

There is a place for RV-Digest-It and similar in your tool bag. The camper next to you may have a totally clogged system and you can help a friend out.


Never had an odor issue that was not traced back to a nearly full tank and the fan running on a windy day.

[3 Happy Campers]

Yes I have a septic system. For 15 years.

Let me restate myself.

A septic system has two main components.
The holding tank & the leach field.

An RV holding tank is like the holding tank of a septic system.
In the holding tank(s) bacteria works on breaking down solids into a liquid called effluent.

The manner in which the liquid leaves the holding tanks is different.

[Herk7769]

Not to be confrontational, but I think you made my point.

The septic system holding tank holds that sludge for weeks sometimes months to totally break it down.

Most RV holding tanks are full in 3 to 5 days when camping and need dumping. Occasionally, they are dumped with less (always top off with water to at least 2/3 full if a partial tank) if your stay is only a day or so.

[crocus]

"An RV holding tank is like the holding tank of a septic system.
In the holding tank(s) bacteria works on breaking down solids into a liquid called effluent."
================================================== ============
Have to agree with herk, as the poop doesn't sit in the RV tank nearly long enough to degrade whatsoever.
And a septic tank system has three parts, not two.
I think we can drop this line of thinking now.
Back to the issue, dezolen has a good point, that the gray water tank can also smell very bad indeed. It should be checked as well.

[OldCoot]

Agree with Crocus & Herk, the problem this fellow is having is a clogged vent(s) or empty drain trap(s).

Crocus is right, a septic system has 3 parts and a holding tank on an rv is just that, a holding tank for a few days and it does not possibly have enough time to even start the degradation of material in that length of time. Adding water softener/soap will encourage that the material breaks up and goes into solution for easier disposal.