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View Full Version : 2920 BH - which tank vent is which?


frank r
06-29-2020, 10:47 AM
I have a 2019 Passport 2920BH, and would like to replace the vent cap on the blackwater tank. Can anyone tell me which vent is for the blackwater tank, and which vent is the graywater? I havenít climbed up yet, but the vents look the same from the ground.

Thank you!

flybouy
06-29-2020, 10:51 AM
The vent stack will be directly over the tanks. Your nose should guide you to the black tank vent.

travelin texans
06-29-2020, 11:05 AM
The black should be directly above the toilet going up through one of the interior walls around the toilet.

frank r
06-29-2020, 11:11 AM
I appreciate the quick response. The 2 vents on my unit are very close to each other, and I don't want to go cutting blindly.

flybouy
06-29-2020, 11:41 AM
Why are going to replace it if it isn't broken?:

frank r
06-29-2020, 11:52 AM
Why are going to replace it if it isn't broken?:

I've been getting alot of odors coming back into the trailer, especially after using the tank flush during dumping. My guess is that the cap is at least partially blocked - I have a 360 Siphon cap laying around, so I was going to put that on.

flybouy
06-29-2020, 12:17 PM
If it were blocked then it would drain properly. The purpose of the vent stack is to let air into the tank to replace the contents going out of the tank or vise versa. If odors are coming into the trailer while flushing the tank it could be the seal in the toilet failing. Does the toilet hold water in the bowl? Do you have a vent in the bathroom open? Any bowing in the coroplast under the black tank?

frank r
06-29-2020, 12:29 PM
If it were blocked then it would drain properly. The purpose of the vent stack is to let air into the tank to replace the contents going out of the tank or vise versa. If odors are coming into the trailer while flushing the tank it could be the seal in the toilet failing. Does the toilet hold water in the bowl? Do you have a vent in the bathroom open? Any bowing in the coroplast under the black tank?

Toilet holds water fine. Odor occurs regardless of whether the bathroom roof vent is open or closed. No bowing in the belly of the TT, and recently had the coroplast dropped (unrelated) and all looked fine.

flybouy
06-29-2020, 12:42 PM
Just a thought. Do you know if your outdoor kitchen sink drains into the blank water tank? Mine does, and and it drains via a Hepvo valve. If that Hepvo valve doesn't seal up the odors will come back into that compartment. I always turn on the water for a few seconds whenever I go to the camper just to keep that valve wet. I do the same for any "P" trap like the sinks. The water can evaporate if not used for any length of time.

frank r
06-29-2020, 01:11 PM
Just a thought. Do you know if your outdoor kitchen sink drains into the blank water tank? Mine does, and and it drains via a Hepvo valve. If that Hepvo valve doesn't seal up the odors will come back into that compartment. I always turn on the water for a few seconds whenever I go to the camper just to keep that valve wet. I do the same for any "P" trap like the sinks. The water can evaporate if not used for any length of time.

The outdoor kitchen on the 2920 (much to my disappointment) does not drain into any tank - it's merely a basin that you have to dump out after each use.

travelin texans
06-29-2020, 02:23 PM
Toilet holds water fine. Odor occurs regardless of whether the bathroom roof vent is open or closed. No bowing in the belly of the TT, and recently had the coroplast dropped (unrelated) and all looked fine.

Confused by the the vent opened or closed?
If the vent is closed the black tank won't drain when you open the valve.

frank r
06-29-2020, 02:48 PM
Confused by the the vent opened or closed?
If the vent is closed the black tank won't drain when you open the valve.

Sorry, i was talking about the roof vent, not the tank vent. I was asked if the odor was possibly being drawn into the trailer through an open roof vent.

JRTJH
06-29-2020, 05:36 PM
If you flush with the bathroom vent fan on, you'll draw "foul air" through the rooftop black tank vent pipe, through the black tank and up the toilet "chute" and into the trailer. It takes several minutes for that "stench" to dissipate and few people do it after learning how the process works...

If you are connected to the campground sewer system AND have the gray tank dump valve open, sewer gas can make its way up the "slinky hose" into the gray tank, up the "free air admittance valve" and if it's malfunctioning, into the vanity cabinet.

Another, less likely potential: If your black tank rooftop vent stack is not secured into the top of the black tank, it may have separated and the black tank odors are coming up from that open 1.5" opening where the "vent stack is missing"....

frank r
06-30-2020, 03:42 AM
If you flush with the bathroom vent fan on, you'll draw "foul air" through the rooftop black tank vent pipe, through the black tank and up the toilet "chute" and into the trailer. It takes several minutes for that "stench" to dissipate and few people do it after learning how the process works...

If you are connected to the campground sewer system AND have the gray tank dump valve open, sewer gas can make its way up the "slinky hose" into the gray tank, up the "free air admittance valve" and if it's malfunctioning, into the vanity cabinet.

Another, less likely potential: If your black tank rooftop vent stack is not secured into the top of the black tank, it may have separated and the black tank odors are coming up from that open 1.5" opening where the "vent stack is missing"....

I appreciate all of the thoughts presented here thus far - thank you!

There doesn't seem to be any rhyme or reason to the odor. I notice it regardless of the roof vent being open or closed. It definitely becomes stronger as the tank fills - on 2 day trips it's barely noticeable, by the end of a 7 day trip it's downright nasty. Tank deodorizer chemicals do nothing. I pretty much never camp anywhere that has in-site sewer hookups, so it's not coming through the graywater. It is definitely the worst just after dumping/flushing the tank, and that smell can linger for days.

I took a better look at the tank vent locations this morning and one is directly above the toilet and the other is above the shower. Since I have the new cap and the install should be very simple, I'll give it a shot before my next trip coming up next week.

frank r
06-30-2020, 03:45 AM
You mentioned the possibility of the vent pipe separating from the black tank - is there an easy way to check this? I imagine that the vent pipe would be secured to the inside of the wall, so it wouldn't feel loose from the roof. Also, I assume that the vent pipe would connect to the top of the black tank, so even dropping the coroplast and looking wouldn't work...

JRTJH
06-30-2020, 07:14 AM
The only way I know to check whether the vent stack is secure in the black tank is to "CAREFULLY" cut away the DICOR sealant around the roof projection, twist on the pipe. DON'T PULL UP ON THE PIPE as some are just pressure fitted into the black tank. If the pipe twists easily, I'd suspect a loose "pipe/tank fitting". If it doesn't turn easily, I'd rule out most of the probability that it's "loose at the tank".... Very few RV's that I've seen have the vent stack "secured in the wall" It's a tight fit, and the framing doesn't allow for much movement, so most are just "stacked between the luan wall panels and held in place by the luan"...

travelin texans
06-30-2020, 07:59 AM
Sorry, i was talking about the roof vent, not the tank vent. I was asked if the odor was possibly being drawn into the trailer through an open roof vent.

The roof vent IS the tank vent. RV toilets are not plumbed like residential toilets, they dump straight into the tank.

frank r
06-30-2020, 08:40 AM
The roof vent IS the tank vent. RV toilets are not plumbed like residential toilets, they dump straight into the tank.

..........

flybouy
06-30-2020, 09:42 AM
I appreciate all of the thoughts presented here thus far - thank you!

There doesn't seem to be any rhyme or reason to the odor. I notice it regardless of the roof vent being open or closed. It definitely becomes stronger as the tank fills - on 2 day trips it's barely noticeable, by the end of a 7 day trip it's downright nasty. Tank deodorizer chemicals do nothing. I pretty much never camp anywhere that has in-site sewer hookups, so it's not coming through the graywater. It is definitely the worst just after dumping/flushing the tank, and that smell can linger for days.

I took a better look at the tank vent locations this morning and one is directly above the toilet and the other is above the shower. Since I have the new cap and the install should be very simple, I'll give it a shot before my next trip coming up next week.

When reading the bolded lines it sounds to me like a leak and the contents leaking accounts for the "lingering" odor.

frank r
06-30-2020, 09:48 AM
When reading the bolded lines it sounds to me like a leak and the contents leaking accounts for the "lingering" odor.

Are you thinking the tank itself is leaking? I can tell you that I have pulled the coroplast since this issue presented itself, and there is no evidence of a septic leak in the belly of the trailer. Also, if it means anything, there is no detectable odor outside of the trailer at any time.

travelin texans
06-30-2020, 09:54 AM
Surely it is, but is there 1/2-3/4 of the toilet bowl filled with water after each flush?
Just trying to cover all possibilities.
I've read that a certain brand of toilet has hidden areas in/around the base, between the bowl & the floor, that waste gets into causing bad odors, might be worth checking out.

flybouy
06-30-2020, 10:35 AM
I'm thinking Danny may be on the right track. If it were me I'd get a new toilet to floor seal and pull the toilet off the floor. Give the toilet a good inspection as well as the floor.

JRTJH
06-30-2020, 04:39 PM
I'd suspect that if it is a black tank leak, once the odor "increases after the 4th or 5th day, it wouldn't "disappear after sitting a week with no trailer use"... Once that smell dries on the top of the tank or on the coroplast under the tank, it's going to be there every time you open the passthrough or every time you flush the toilet... Odors from the black tank don't "come and go" like that.

I'd guess that it's air infiltrating the black tank contents "somehow" and migrating up into the trailer cabin "somehow"...

If it was "liquid escaping the tank" the odor would linger much MUCH longer than a day or two.....

The toilet, if it's a Thetford, is a likely source, as is the foam rubber seal that is used in trailers in place of the wax seal that's used in S&B houses.

skids
07-01-2020, 05:55 AM
Is there a way of removing the cap from the pipe vent and run some water into it to ensure that it isn’t blocked? You are not putting the cabin on a negative pressure with a fan are you?

sourdough
07-01-2020, 07:26 AM
Surely it is, but is there 1/2-3/4 of the toilet bowl filled with water after each flush?
Just trying to cover all possibilities.
I've read that a certain brand of toilet has hidden areas in/around the base, between the bowl & the floor, that waste gets into causing bad odors, might be worth checking out.


The Thetford in our 14 Cougar HC had recessed pockets down every side of the plastic column supporting the porcelain bowl. When the bowl seal started leaking the liquids accumulated in those pockets and put out a stench. The smell would go away if you didn't use it and let it dry but as soon as you began using it they came back. I just replaced the Thetford that came in our 2020 and they have, thankfully, redesigned the inside of that column to more reflect a Dometic and there are no pockets to retain the liquids.

OP says that the issue is really prevalent when running the black tank flush and apparently pushing those odors back into the camper? If the ball seal is good it would seem to be either the floor seal or the vent.

flybouy
07-01-2020, 07:39 AM
Logically there are 2 scenarios.
1. There is a liquid leak of black tank contents.
2. There is a condition that is causing the odor (air) from the black tank to infiltrate the interior of the trailer.

If you have confirmed there is no leak that leaves #2. The possibilities are several,
creating a negative pressure by running an exhaust fan without providing an exchange of air such as another vent opened or window opened and the neg pressure is great enough to get the odor past the toilet itself or around the floor where the toilet is mounted. Using the bathroom vent fan while flushing the toilet will create a "rush" of blank tank air into the bathroom. The other possibility is having a vent open close to the stack vent that allow the air from the black tank to enter inside.

If I'm missing something here someone please point it out as I don't think it's a ghost with a gastric issue hanging around.

frank r
07-01-2020, 12:59 PM
Logically there are 2 scenarios.
1. There is a liquid leak of black tank contents.
2. There is a condition that is causing the odor (air) from the black tank to infiltrate the interior of the trailer.

If you have confirmed there is no leak that leaves #2. The possibilities are several,
creating a negative pressure by running an exhaust fan without providing an exchange of air such as another vent opened or window opened and the neg pressure is great enough to get the odor past the toilet itself or around the floor where the toilet is mounted. Using the bathroom vent fan while flushing the toilet will create a "rush" of blank tank air into the bathroom. The other possibility is having a vent open close to the stack vent that allow the air from the black tank to enter inside.

If I'm missing something here someone please point it out as I don't think it's a ghost with a gastric issue hanging around.

I am 95% certain that their is no tank leak. I know for a fact that the coroplast is not sealed well enough to conceal a leak (had a water pump leak that I first noticed because of the water running out multiple places in the belly of the trailer).

I do not see it being a negative pressure issue, as the odor shows up regardless of vents/windows being open/closed or the rooftop A/C being on/off.

The other popular idea is that this is being caused by a faulty toilet/floor seal. I have a trip coming up next week, and do not have the time to tear into that beforehand - so for now I will replace the vent cap (since I already have it and the install will take only a few minutes) and see if that does anything at all. If not - which I assume will be the case - I'll pull the toilet when I get home.

Again - I appreciate all the of the guidance thus far.

sourdough
07-01-2020, 02:08 PM
Frank pulling the toilet and placing it back might, MIGHT take 30 minutes at the very most if you have the seal. Disconnect the 2 retaining nuts and water line, lift toilet and remove the old seal (just pull it down/off the toilet drain, slip the new one on, drop it back down over the bolts (make sure the seal is inserted into the drain hole correctly) then reconnect. It goes really quick. Of course, hopefully the replacing the vent does the trick.

JimSchwenk
07-05-2020, 08:13 AM
Just a thought. Do you know if your outdoor kitchen sink drains into the blank water tank? Mine does, and and it drains via a Hepvo valve. If that Hepvo valve doesn't seal up the odors will come back into that compartment. I always turn on the water for a few seconds whenever I go to the camper just to keep that valve wet. I do the same for any "P" trap like the sinks. The water can evaporate if not used for any length of time.

Boy, that sounds familiar. My 2016 26RB Campfire has a familiar stench every time I open the big door to the outside kitchen. I always run a bunch of water into the sink there, but overnight it leaks out the sink drain. Of course with the overhead door open you don't notice it, but I keep it closed most of the time, especially when I leave for a few days.
I have no idea where the Hepvo valve is, can't see it by removing the under sink access panel. Been like this since new.
My bathroom sink is just to the left and above that outside sink; you'd think they would have drained it that way but I guess not enough pitch to have used a standard P-trap setup from the lower sink drain.

vulcanwayne
07-05-2020, 02:18 PM
Check to see if your toilet is a Dometic model 300? If it is then contact Dometic, they have a problem with that model. I just experienced the same problem and they sent me a new toilet. They have a 2 year warranty period.

Bullet19
07-05-2020, 04:15 PM
I own a 2019 Bullet 243BH and also recently contacted Dometic for a replacement toilet. Given the Passport and Bullet share many similar components it is likely you also have the problem toilet. There is no official recall of the unit but if you call they will offer you a replacement. Either a ceramic bowl for a small upgrade $ or the newly designed 300.

See this video ->https://www.youtube.com/watch?v=FzHEetmbQtM

frank r
07-06-2020, 03:17 AM
Check to see if your toilet is a Dometic model 300? If it is then contact Dometic, they have a problem with that model. I just experienced the same problem and they sent me a new toilet. They have a 2 year warranty period.

It is a Dometic, but I don't see a model # anywhere.

As expected, the new roof vent hasn't helped.

vulcanwayne
07-06-2020, 03:56 AM
You will need both the model and serial number. They are located on a sticker on the base near the flush lever valve.

Bullet19
07-06-2020, 04:02 AM
Model # and serial will be on a sticker low to the floor, right hand side. I used my phone to take a picture of mine to read. It was easier than getting my head stuck between the toilet and the tub.

frank r
07-06-2020, 08:27 AM
My unit is the Dometic 300. I just spent 93 minutes on hold with Dometic customer service, only to be disconnected while my call was being answered. I called back, got an operator and was told to "call back after lunch". I have on words...or at least no words that I can use in polite company.

vulcanwayne
07-06-2020, 08:34 AM
When I called I was on hold for 30 minutes and then was told that a replacement was needed but I should call back in a couple of days to get my info in their computer system that they were only two operators working. I advised her that I was not willing to go through on hold etc. again and that all she lacked was my address. She then put the info in and the unit was delivered in a couple of days.

frank r
07-06-2020, 08:42 AM
Thank you for the tip - I'll be sure to push the issue if they try to push me off again.

JRTJH
07-06-2020, 09:38 AM
Thank you for the tip - I'll be sure to push the issue if they try to push me off again.

Telling a customer to "call back after lunch" is despicable and should NEVER occur. I'm not defending Dometic when I say that right now, most CS departments are working with limited staffing, many at half staffing levels. After being completely shut down for the past 2-3 months, the "rush of business" has tripled or quadrupled and the staff is simply inadequate to give "pre Covid attention"....

Try calling Ford CS, GM CS, Keystone CS, Furrion CS, heck, try calling the local WalMart auto center and see how long you sit on hold....

These aren't "normal times" and expecting "pre covid attention" just ain't possible in nearly every business situation.

Give 'em a little slack, they are not "intentionally picking on you" ...

frank r
07-06-2020, 09:42 AM
Telling a customer to "call back after lunch" is despicable and should NEVER occur. I'm not defending Dometic when I say that right now, most CS departments are working with limited staffing, many at half staffing levels. After being completely shut down for the past 2-3 months, the "rush of business" has tripled or quadrupled and the staff is simply inadequate to give "pre Covid attention"....

Try calling Ford CS, GM CS, Keystone CS, Furrion CS, heck, try calling the local WalMart auto center and see how long you sit on hold....

These aren't "normal times" and expecting "pre covid attention" just ain't possible in nearly every business situation.

Give 'em a little slack, they are not "intentionally picking on you" ...

Oh,I understand completely and wasn't angry about the hold time. My frustration was over being disconnected after sitting on hold so long.

Anyway, I called back, got a very nice lady after a few minutes wait. She was all set to process my warranty claim when she asked me for the trailer's VIN...

...guess I'll try back tomorrow.

frank r
07-07-2020, 10:45 AM
Well, supposedly my new-and-improved stench-free Dometic Model 300 is being shipped out later this week.

Wish me luck...

On a serious note, thank you for all of the input. I will keep you posted on the results, but after we get back on Sunday, I don't have another trip booked until early August.