Black tank roof vent

[CaptDan]

I have a 397TH. I believe I may have a stoppage somewhere in my black tank (#1) roof vent piping. I bought a snake at HD this afternoon but it's too hot to go up there right now. I read on a FB Group that the Black tank vent piping might be connected to the Grey Tank #1 via a Wye. (The guy noted that he needed to fuss with it to make sure it went down to the black tank. He did not mention what rig he had. Does anyone with a 397 (2020) know if the Black Tank #1 has a dedicated vent or a "Y" with Grey #1 - I would like to avoid pulling everything out of the pass thru and take down walls/etc. Thanks

[howson]

CaptDan -- from what I can tell from the information GD allows the moderators to view, the black tank vents (both the forward and rear) are straight shots on a 397TH.

Both grey tanks have a "T" or "Y", but not the blacks.

Cate&Rob , TucsonJim or Country Campers -- please double check.

Howard

[Cate&Rob]

CaptDan -- from what I can tell from the information GD allows the moderators to view, the black tank vents (both the forward and rear) are straight shots on a 397TH.

Both grey tanks have a "T" or "Y", but not the blacks.

Cate&Rob , TucsonJim or Country Campers -- please double check.

Howard

It is common for tanks grouped together to all vent through the same pipe to the roof (minimizes number of roof vents). I would expect that the forward black and grey tanks vent through the same roof opening. The galley grey might also be connected to this same roof vent. The aft black/grey tank will probably have its own roof vent.

Rob

[Yoda]

I have a 397TH. I believe I may have a stoppage somewhere in my black tank (#1) roof vent piping. I bought a snake at HD this afternoon but it's too hot to go up there right now. I read on a FB Group that the Black tank vent piping might be connected to the Grey Tank #1 via a Wye. (The guy noted that he needed to fuss with it to make sure it went down to the black tank. He did not mention what rig he had. Does anyone with a 397 (2020) know if the Black Tank #1 has a dedicated vent or a "Y" with Grey #1 - I would like to avoid pulling everything out of the pass thru and take down walls/etc. Thanks

First thing to check for is a wasp nest at the top - found that on my rig while doing a solar install when I accidentally knocked the cap off. It should pull straight up to get it off.

[CaptDan]

Thanks guys. I ran the snake it's entire length (25') and never felt any obstruction. I guess sorta over kill. Next time I need to limit the insertion to what I need to just make it into the tank. When I re-coiled it the last 2-3 feet, it had a couple small clumps of hair but nothing else (no poo - no TP). My wife washes her hair in the main sink (?). Grey tank #1 (?) So I guess I need to pull everything out of the pass-thru and hope to be able to trace the vent piping from the black tank to see if is dedicated or shared. In any event the smell seems to have been resolved (for now). Unfortunately it may have to do more from rinsing it out for about 30 minutes rather than the snake ... will update if I learn anything. I really hope it's not tied in with Grey #2. I'm really starting to get angry at how GD designed these pluming systems. My wife knocked over the toilet and broke the floor flange. Unlike other brands - you cannot simply "unscrew" the flange and put a new one in. The flange is secure in the down pipe and probably glued as well. Why? Others on line have had to remove the entire piping from flange to tank - just to fix the flange. Right now I have a temporary flange repair kit on it but will be curious as to how long that lasts. Thanks again guys.

[Cate&Rob]

CaptDan

Where is the smell coming from that you are trying to resolve? If it is from under a sink or up through the sink drain, the culprit is likely a stuck open or stuck closed AAV (Air Admittance Valve). This will be hand tightened into the top of a tall pipe under the vanity beside the sink. You can get a replacement at Home Depot or similar.

Rob

[CaptDan]

Black tank smell. Hard to determine where since as soon as we flush the toilet, it seems to be in several spots at same time, bathroom, bedroom, by refrigerator, couch, etc. Its not the grey tank.

[Cate&Rob]

Black tank smell. Hard to determine where since as soon as we flush the toilet, it seems to be in several spots at same time, bathroom, bedroom, by refrigerator, couch, etc. Its not the grey tank.

I would suspect a broken (rather than plugged) vent stack. Particularly if this stack goes up a wall common to the areas that you mention. Since black and grey tanks often have a combined vent stack, black tank odours can find their way out a broken or disconnected grey tank vent pipe.

Rob

[CaptDan]

Was trying to avoid (or put off) pulling everything out of the pass-thru but if the smell returns, will do so and visually inspect the vent pipe leading out of the black tank and will also verify if it is a dedicated vent pipe or combines with the grey tank via a "Y". It is possible the pipe leaks on it's way to the roof - it's just hard to believe.... Thanks

[Jlawles2]

CaptDan Dan, have you checked the air admittance valve? Both of the ones in my camper were less than baby finger tight.

[CaptDan]

We have black tank orders not grey. It only happens when we flush the toilet. Unless I'm mistaken, unlike the grey tank plumbing, there isn't any air admittance valves on the black tank.
however, if I find out that the grey tank vent is connected to the black tank vent - it might be related somehow.

[Tom in PGH]

Might want to take a short trip up to the roof and see how many vents there are and where they are located. I only have one vent on my 303, so I know that everything is connected prior to the vent.

[CaptDan]

UPDATE: I crawled into the pass thru and found three (3) vent pipes leading away from Black #1, Grey #1 and Grey #2. All three then make a turn vertically up behind the shower and disappear. No visual "Y" was visible. I then pulled up my GD diagrams they gave me a year ago and noted that not only are the black/grey tanks in reverse positions (Black on left - Grey on right) the diagram shows four (4) vent lines going to the roof. I only have three (3) vents on the roof. One Black vent aft (Black #2 - rear bathroom). One white one in the middle and one more Black vent up forward. You would think (hope) that the two (2) grey tanks would be "Y" together at this stage but (alas) I called GD and they finally informed me that a) there is no updated diagram (??) and b) Black #1 and Grey #1 are joined in a "Y" (somewhere). That sorta explains how I got hair on the snake instead of toilet paper and poo. I went down into the Grey tank - not the black tank. They did ask me to check the air actuator valve under the front bathroom sink (yo Joseph). I argued with them stating that the smell is definitely black tank smell and only time it happens is when we flush that toilet and the smell is almost immediate everywhere - how could the sink valve play any part - well ... now the light comes on with regards to my new realization that my black/grey #1 system are now theoretically (and now actually) "connected". Wonderful. I had months ago tightened up on the air actuators for both the rear sink and island sinks when we had grey tank odors. I never inspected the front bedroom actuator. Well, long story short, I went to the bathroom sink reached up and ended up being able to screw it down about 6 turns before it got hard to turn (hand tight). Flushed the toilet - zero smell - anywhere. tried again - zero smell - even sticking my head near the toilet seat. WHO WOULD HAVE THUNK? So crossing my fingers that does the trick as the tank gets more full/time, etc. Ridiculous. I need to copy/paste all of this into my Momentum notes.... Now if I can just get 3 jacks replaced we can leave Sheridan, Wyoming after 55 days and continue to argue with the insurance company..

[Cate&Rob]

CaptDan

Good to learn that you have found the problem. No surprise here . . . since may of us have found problems with the AAVs. There are better quality ones available . . . a good place to spend a few dollars.

One comment . . . the white vent on the roof is most likely an attic vent. You probably have one holding tank vent stack for the front tanks and one for the rear.

Rob

[CaptDan]

You're kidding, aaaah! Makes sense since it doesn't look like any I've seen on Amazon, etc. Where does GD describe having a attic vent?? hahaha - I think I know the answer. Thanks - appreciated.