Why the sewer smell?

[Kudzu]

This has me stumped. 2000 model 5th wheel we are currently living in.



Black tank lasts about 7 days before it needs to be dumped. At that point, when it is full it starts to stink really bad in the 'basement' area and the smell gets into the bathroom.


I can find no leaks and it only smells when it is full or really close. Gage is no reliable. Dump and rinse and air it out and it good till next weekend.



Any ideas what I am missing?

[Midnightmoon]

Just guessing, but it could be that as the tank gets close to full, it isn't able to vent properly and causes the smell in and around the tank area.

[RogerR]

Lots of other posts on smells. Try using the search engine above. After that a frequent culprit is the Studor type vent(s) that allow air in and sometimes fail. Another idea is back draft from the roof. Alternatively, you may have a bad connection in the walls somewhere or blocked roof vent.

Suggestion. When clean and at home hook a blower to the roof vent and try to find the air leak then.

Last thought, if full, could it be backing up into shower pan or elsewhere?

[The Gritz Carlton]

Are you in a fixed location or traveling? Do you use chemicals each time you dump? With it being 23 years old, you may have plumbing parts and pieces trying to separate. Dump more often and see if that helps. Chemicals work good but can get diluted the more full the tank gets. Try adding more chemicals half way through your dump cycles.

[JFlightRisk]

Originally Posted by Kudzu

This has me stumped. 2000 model 5th wheel we are currently living in.



Black tank lasts about 7 days before it needs to be dumped. At that point, when it is full it starts to stink really bad in the 'basement' area and the smell gets into the bathroom.


I can find no leaks and it only smells when it is full or really close. Gage is no reliable. Dump and rinse and air it out and it good till next weekend.



Any ideas what I am missing?

My BIL had the same problem, but his TT was only two years old and swore his black tank flusher was getting it clean enough. He was wrong. I put a clear sewer fitting on his discharge, and I went inside with a flushing wand on a hose. I told him to watch what came through the clear part and tell me when the water ran clean. I took a good 15 minutes of me rinsing it, and he was amazed at what came out. Might be your same issue.

[Kudzu]

Originally Posted by The Gritz Carlton

....With it being 23 years old, you may have plumbing parts and pieces trying to separate. Dump more often and see if that helps. .......

That is what I was thinking but that is why I mentioned no leaks. Have had the belly pan off and looked. But it ONLY does it when it is full which makes me lean toward a leak. But it doesn't drip! Zero signs of a leak.... other than the smell.



We are stationary. Living on land we bought preparing to build a house.
don't use chemicals at all.



And yes dumping more often stops it because it only does it when it is full or I assume full. No way to no for certain. But I assume it is a certain level and that has always said leak to me.

[Kudzu]

Use both, but again, it only happens after about a week if we are both here. Wife travels with work and when she is gone and it just me, no problem come the weekend when I usually dump it.



Got to be related to level in the tank. Real head scratcher.

[SmokerBill]

Originally Posted by Midnightmoon

Just guessing, but it could be that as the tank gets close to full, it isn't able to vent properly and causes the smell in and around the tank area.

I agree. When the tank level rises it can close off the in-tank opening to the roof vent.

Try dumping every 5 days. It should empty fine if it's 3/4 full.

[Randyman69357]

Could be just an air leak, say around the base of the toilet so no water or sewage escaping. When the tank gets full enough the sewage will cover over the vent. Only place left is up through the toilet, or the base gasket of the toilet.

[texasjayco]

Are you sure it’s not the batteries?
I had the same issue with my previous 5th wheel, and turned out it was a bad battery!!
Smelled just like the black tank.

Mark

[Marcm157]

The tank could be cracked or be separating slightly from the plumbing above when the weight of the full tank pulls it down. It will be very hard to see as you need to get a view of the top of the tank when full. An inexpensive borescope will be your best friend here..

[pc55]

Originally Posted by Midnightmoon

Just guessing, but it could be that as the tank gets close to full, it isn't able to vent properly and causes the smell in and around the tank area.

they say to dump it when it burps when you flush. The air vent is lower than the toilet outlet so when it gets full the sewer gasses are not venting out the roof.

[Ringneks]

Why do you not use chemicals? You may not be getting the tank cleaned out all the way.

Originally Posted by Kudzu

That is what I was thinking but that is why I mentioned no leaks. Have had the belly pan off and looked. But it ONLY does it when it is full which makes me lean toward a leak. But it doesn't drip! Zero signs of a leak.... other than the smell.



We are stationary. Living on land we bought preparing to build a house.
don't use chemicals at all.



And yes dumping more often stops it because it only does it when it is full or I assume full. No way to no for certain. But I assume it is a certain level and that has always said leak to me.

[ARoamer]

Agree if your toilet "Burps" your vent is not venting. Fill the bowl with water and flush, and if you get a bubble of air before it drains it's not venting properly. Also, check your roof vents. My grey tank vent was venting into my attic. Kept smelling foul odors and took of my grey tank roof vent and found the vent pipe cut flush to the roof (possibly to male applying roof membrane easier at the factory?) and a misaligned unglued slip pipe fitting extension that would not stay connected due to the misalignment. Poor pic, but see the foil roof insulation.
Also not a big fan of chemicals, but I will occasionally use them during summer hot spells, being a mix of fabric softener and detergent.

[TomC_AZ]

Just a couple other ideas that might be causing this.

Make sure the toilet seals are good and lubricated, we have a newer trailer and found out that I needed to be more kind to our seal and have not had any issues since.

Also possibly getting one of these to help flush things out better?
https://www.amazon.com/dp/B089F9FCSM...roduct_details

It may potentially be the grey tank as well, those smells can get bad!! Most people don't realize that the grey tank can and usually is way worse than the black tank. This will help you flush that out as well. I am amazed that they don't put a flush on those tanks, ever!! (at least I have never seen one on any level or price of trailer/coach I have been in)

[The Gritz Carlton]

You've defined your problem. Letting older tank get way to full before emptying and not using chemicals...which not only helps control odor but also breaks waste down. Why don't you try rectifying these two issues and report back later? Lots of mechanical suggestions here but the real issue is obvious.

[citgodan]

Originally Posted by texasjayco

Are you sure it’s not the batteries?
I had the same issue with my previous 5th wheel, and turned out it was a bad battery!!
Smelled just like the black tank.

Mark

The battery issue (smell) will be there no matter what level the black tank is at. When I had the battery issue, I dumped and rinse the black tank assuming that was my issue, but the smell never went away.

It was later in the day when I was searching for the foul smell when I popped open the battery compartment and was blown away with the smell and hot battery.

[The Gritz Carlton]

Kudzu has left the building....I think this thread is dead.

[hikerjohn7]

Originally Posted by Kudzu

This has me stumped. 2000 model 5th wheel we are currently living in.



Black tank lasts about 7 days before it needs to be dumped. At that point, when it is full it starts to stink really bad in the 'basement' area and the smell gets into the bathroom.


I can find no leaks and it only smells when it is full or really close. Gage is no reliable. Dump and rinse and air it out and it good till next weekend.



Any ideas what I am missing?

Seven days between black tank dumps sounds kind-of long. I have a class A and after about 3 days it smells if the toilet is not flushed quickly. Also, if you run the exhaust fan, that pulls the fumes out of the toilet's down-pipe after a few moments.

[VKC]

Wash the vent tube with a water hose to make sure a dirt dauber hasn’t built a nest in the vent.