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 haven’t 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

Quote:

Originally Posted by flybouy

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

Quote:

Originally Posted by flybouy

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

Quote:

Originally Posted by flybouy

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

Quote:

Originally Posted by frank r

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

Quote:

Originally Posted by travelin texans

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

Quote:

Originally Posted by JRTJH

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

Quote:

Originally Posted by frank r

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

Quote:

Originally Posted by travelin texans

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

Quote:

Originally Posted by frank r

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

Quote:

Originally Posted by flybouy

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.

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