Home » Public Forums » GMCnet » Flush mount black tank vent? (Does it exist?)
| Flush mount black tank vent? [message #355079] |
Sun, 24 May 2020 13:52  |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
|
Senior Member |
|
|
So maybe a stupid question as i have the time to ask it.... does anyone make a flush mount RV sewer vent?
When Hughes built these coaches i'm not sure if they ever thought 2 AC units would ever be put on the roof....anyways to make a long story short i have a second AC i could put on but the black tank vent is basically in the way.  Some might say...just move it...and the mechanic in me says sure thing....but none of these units have fiberglass bathrooms like the GM models do and they ran the pipe from the tank up the hallway side corner behind the toilet hidden behind a "box".
In order to move it i have to also move "the box" and my cabinet maker wife said "leave it alone or your going to open up a whole can of worms".....so the only other choice other than redoing the whole bathroom, if i want to add the AC is a flush mount black tank vent that will be just under the none fastened part of the AC unit [the part that is held up off the roof].
So what do you think.....does one exist? Bad idea as it is possible the AC might suck in fumes from the tank vent? Options? I know i can not put the second AC on altogether and install some really expensive vents instead [i want one to be able to run in reverse].
Rich Mondor,
Brockville, ON
77 Hughes 2600
|
|
|
|
|
|
|
|
|
|
| Re: [GMCnet] Flush mount black tank vent? [message #355087 is a reply to message #355083] |
Sun, 24 May 2020 16:30  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
|
Senior Member |
|
|
Problem wit a flush mounted sewer vent is when snow and heavy rain will
drain down the vent and possibly fill your sewer tank.
On Sun, May 24, 2020 at 2:09 PM John Wright via Gmclist <
gmclist@list.gmcnet.org> wrote:
> This is true when more clearance is needed. When your parked the AC unit
> doesn’t know which way it is facing.
>
> J.R. Wright
> GMC Great Laker MHC
> GMCGL Tech Editor
> GMC Eastern States Charter Member
> GMCMI
> 78 GMC Buskirk 29.5’ Stretch
> 75 GMC Avion (Under Reconstruction)
> Michigan
>
>
>> On May 24, 2020, at 4:48 PM, Dennis Sexton via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>>
>>
>> Rich
>> Some have installed the rear AC unit reverse direction - would that give
> you the clearance you need.
>> Putting the AC unit on "backwards" apparently has no affect on its
> performance.
>>
>> Dennis
>>
>> 6cuda6 wrote on Sun, 24 May 2020 13:52
>>> So maybe a stupid question as i have the time to ask it.... does
> anyone make a flush mount RV sewer vent?
>>>
>>> When Hughes built these coaches i'm not sure if they ever thought 2 AC
> units would ever be put on the roof....anyways to make a long story short i
>>> have a second AC i could put on but the black tank vent is basically in
> the way. :cry: Some might say...just move it...and the mechanic in me says
>>> sure thing....but none of these units have fiberglass bathrooms like
> the GM models do and they ran the pipe from the tank up the hallway side
> corner
>>> behind the toilet hidden behind a "box".
>>>
>>> In order to move it i have to also move "the box" and my cabinet maker
> wife said "leave it alone or your going to open up a whole can of
>>> worms".....so the only other choice other than redoing the whole
> bathroom, if i want to add the AC is a flush mount black tank vent that
> will be
>>> just under the none fastened part of the AC unit [the part that is held
> up off the roof].
>>>
>>> So what do you think.....does one exist? Bad idea as it is possible the
> AC might suck in fumes from the tank vent? Options? I know i can not put
>>> the second AC on altogether and install some really expensive vents
> instead [i want one to be able to run in reverse].
>>
>>
>> --
>> Dennis S
>> 73 Painted Desert 230
>> Memphis TN Metro
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
|
|
|
|
| Re: Flush mount black tank vent? [message #355100 is a reply to message #355079] |
Sun, 24 May 2020 22:11 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
|
Senior Member |
|
|
JimK,
I hope I'm not being a wise-ass here, but a 30 gallon tank (about as small as we GMCers have) should hold about 3,920 inches of rainfall entering a 1 1/2" pipe opening. That's 326 feet of rain. Unless the tank is already brim-full, I wouldn't worry about it. 
HTH
rick Staples
Rick Staples, '75 Eleganza, Johnstown, CO
"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
|
|
|
|
|
|
| Re: Flush mount black tank vent? [message #355105 is a reply to message #355102] |
Mon, 25 May 2020 09:20 |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
|
Senior Member |
|
|
Not sure, i would have to see if it does.
And that "fresh air" is what im worried about.....lol.
RF_Burns wrote on Mon, 25 May 2020 08:17Does the A/C unit bring in outside "fresh" air when running?
If so you might not want a black tank vent in close proximity to it... the air might be just be "too fresh"... if you get my drift...
Rich Mondor,
Brockville, ON
77 Hughes 2600
|
|
|
|
|
|
|
|
|
|
|
|
| Re: [GMCnet] Flush mount black tank vent? [message #355113 is a reply to message #355109] |
Mon, 25 May 2020 13:46 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
|
Senior Member |
|
|
If you can get to that vent inside the coach you might be able to install an Air Admittance Valve and eliminate the roof vent. I'm not a big fan of these valves but they are code compliant. Just an idea, Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
|
|
|
|
| Re: [GMCnet] Flush mount black tank vent? [message #355114 is a reply to message #355113] |
Mon, 25 May 2020 13:54 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
|
Senior Member |
|
|
Assuming (yeah, I know) that you would probably only need the rear A/C unit when you were stopped (for the night?), one of those "weather vane" type venturi extractors on a maybe extended vent pipe could serve to get the "fumes" away from the A/C. I'm not even sure that our coach A/C units use outside air, so no real worry!
D C "Mac" Macdonald
Amateur Radio K2GKK
Since 30 November '53
USAF and FAA, Retired
Member GMCMI & Classics
Oklahoma City, OK
"The Money Pit"
TZE166V101966
'76 ex-Palm Beach
k2gkk + hotmail dot com
________________________________
From: Gmclist on behalf of Hal StClair via Gmclist
Sent: Monday, May 25, 2020 13:46
To: gmclist@list.gmcnet.org
Cc: Hal StClair
Subject: Re: [GMCnet] Flush mount black tank vent?
If you can get to that vent inside the coach you might be able to install an Air Admittance Valve and eliminate the roof vent. I'm not a big fan of
these valves but they are code compliant. Just an idea, Hal
--
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1975 Eleganza II, 101230,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: [GMCnet] Flush mount black tank vent? [message #355118 is a reply to message #355109] |
Mon, 25 May 2020 18:43 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
|
Senior Member |
|
|
Richard,
you are correct, however the rv manufactures do not want it to happen and
also easy to seal around the pipe at a higher level.
On Mon, May 25, 2020 at 8:48 AM Emery Stora via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Rich
> I once put a microwave into the top shelf of the cabinet opposite the
> bathroom. I found that the vent pipe from below wanted to go through the
> microwave. I cut the vent pipe below the microwave and then used radiator
> hoses with bends to vent around the microwave and then up to the existing
> roof vent. This worked very well for me.
>
> It will work just fine with bends in the pipe.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>
>> On May 25, 2020, at 8:22 AM, 6cuda6--- via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> I think I'm in a pickle and am going to have to just shelve the second
> a/c till i figure out the vent and bathroom deal.
>> --
>> Rich Mondor,
>>
>> Brockville, ON
>>
>> 77 Hughes 2600
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
|
|
|
|
| Re: [GMCnet] Flush mount black tank vent? [message #355122 is a reply to message #355118] |
Mon, 25 May 2020 22:00 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
|
Senior Member |
|
|
I was going to suggest an AAV, but I see Hal already beat me to it.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
|
|
|
|
| Re: [GMCnet] Flush mount black tank vent? [message #355133 is a reply to message #355113] |
Tue, 26 May 2020 08:59 |
 |
Richard RV
Messages: 631
Registered: July 2012
Location: Full-timer for 12 years, ...
Karma: -17
|
Senior Member |
|
|
Air admittance valves are code compliant for most residential construction codes, but I'm not sure about installation in an RV, particularly on a black tank vent. A residential toilet has its own built in water seal that prevents sewer gases from rising through the toilet, an RV toilet does not. How an AAV would play with a ventless and trap-less toilet, I do not know, but it'd be a good idea to do your homework before cutting and removing the existing vent.
Emery's solution of using radiator hose and hose clamps seems simplest and least likely to cause a stinky gotchya.
While on the subject of venting and traps, Hepvo waterless traps should replace P-traps in all RVs at the first opportunity. Easy to install, frees up some room under the sinks, no need to winterize and gets rid of the tiny black flies that use the drains' trap water as a watering hole.
Richard
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemont waiting its turn
|
|
|
|
| Re: [GMCnet] Flush mount black tank vent? [message #355139 is a reply to message #355133] |
Tue, 26 May 2020 09:13 |
GMC.LES
Messages: 505
Registered: April 2014
Karma: -2
|
Senior Member |
|
|
The vent pipe doesn’t care if it runs horizontal. Why not reroute the pipe horizontally along the top edge of the bathroom wall and have your wife build a cover to hide it.
The AAV would be a poor choice IMO because it is basically a 1-way valve, letting air into the system. The problem is they won’t let air out and could conceivably allow the Ptrap contents and tank gasses to get blown into the coach should something pressurize the holding tank.
Les Burt
Montreal
'75 Eleganza 26'
> On May 26, 2020, at 9:59 AM, Richard via Gmclist wrote:
>
> Air admittance valves are code compliant for most residential construction codes, but I'm not sure about installation in an RV, particularly on a
> black tank vent. A residential toilet has its own built in water seal that prevents sewer gases from rising through the toilet, an RV toilet does
> not. How an AAV would play with a ventless and trap-less toilet, I do not know, but it'd be a good idea to do your homework before cutting and
> removing the existing vent.
>
> Emery's solution of using radiator hose and hose clamps seems simplest and least likely to cause a stinky gotchya.
>
> While on the subject of venting and traps, Hepvo waterless traps should replace P-traps in all RVs at the first opportunity. Easy to install, frees
> up some room under the sinks, no need to winterize and gets rid of the tiny black flies that use the drains' trap water as a watering hole.
>
> Richard
> --
> '77 Birchaven TZE...777;
> '76 Palm Beach with 18,477 verified miles;
> ‘76 Edgemonte
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: [GMCnet] Flush mount black tank vent? [message #355167 is a reply to message #355139] |
Tue, 26 May 2020 21:01 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
|
Senior Member |
|
|
I agree with what Les said. An AAV is a great idea IFF there's another vent for the system. I seem to recall that even in a house, if you have a septic system like some of us do, you need at least one actual unrestricted vent to atmosphere to prevent possible pressure build up. In an RV, I think it's good to have at least 2 vents on different side of the tank to ensure one of them is always above the liquid level. Still, I plan to replace the vent beside the refrigerator with an AAV some day, as it enters the tank at the same point as the rear vent (GMC wet-bath coach) does, and so is superfluous for tank venting. (It's just here to be sure the water seal is not sucked out of the sink P-trap, as code requires if said trap is over 4' from the main stack/vent.)
Also, some have questioned the proximity of a vent to the roof A/C. I know my 2 ancient Duo-Therms don't have any connection to draw in or exhaust outside air, and I suspect most roof A/Cs are the same, but I'm not an expert on newer models. Even without a direct air intake, many roof A/Cs aren't sealed all that well, so odor could be an issue.
Finally, in my previous comment about rain into an open pipe, I should have specified that I assumed that no water would be funneled off the roof into the vent. As JimK rightly pointed out, you want the pipe to "stand proud" (as the Brits would say) from the roof for 1/4" or so to properly seal it, and prevent funneling.
My .02, HTH
Rick Staples
Rick Staples, '75 Eleganza, Johnstown, CO
"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
|
|
|
|
| Re: Flush mount black tank vent? [message #355171 is a reply to message #355079] |
Tue, 26 May 2020 22:10 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
|
Senior Member |
|
|
Yeah, I guess an air admittance valve would be a bad idea if it was on the only vent line. My GMC finished coach has two vents to roof. I have no idea what Hughes did.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
|
|
|
|
Goto Forum:
Current Time: Fri Apr 04 01:57:25 CDT 2025
Total time taken to generate the page: 0.01105 seconds
|
GMCforum
Search
Help
Register
Login
Home
