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11-13-2022, 12:45 PM
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#1
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Almost There
Join Date: Sep 2020
Location: Ontario, Canada
Posts: 75
Year: 2004
Coachwork: Thomas Built Freightliner. Allison 2000 tranny
Chassis: Freightliner FS-65 (dognose)
Engine: Mercedes MBE 906 six cylinder diesel
Rated Cap: 35 feet long
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Venting my gray tank
I’m planning on having a 40 gallon gray tank in my skoolie. Only a kitchen sink, a bathroom sink and a shower will drain into it. No urine. The drains will have Hepvo valves, so no P traps that might lose their water and allow smells into the bus.
From research in this forum and elsewhere, I assume I need to vent the gray tank. When wastewater flows into it, presumably (smelly) air in the tank will be displaced that has to escape somewhere.
I assume that the vent must be higher than any fixtures that drain into it. Do I want to vent the tank as high up as possible so the smell does not blow back into an open window? That pretty well means drilling a hole in the roof that I’ll need to make weathertight. Thoughts on placement?
Those of you who have done such venting, I’d appreciate details. What diameter pipe/tubing did you use? Is 1 ¼ inch enough? What kind of vent did you mount in the hole you drilled in the roof, that lets gas out but doesn’t let rain or critters in?
Thanks.
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11-13-2022, 01:47 PM
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#2
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Bus Crazy
Join Date: Jan 2020
Location: Fraser Valley British Columbia
Posts: 1,043
Year: 2007
Coachwork: Thomas
Chassis: Freightliner
Engine: C7 Cat
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Hi David
Yes the vent goes thru the roof on an rv tank similar to a house vent. The higher the better when venting, (think of a fireplace chimmney creating draft) the attached pic is the standard rv vent cap, your 1.25 abs would go thru the roof and into this cap then sealed with dicor self levelling sealant.
FYI your kitchen sink is considered black water as kitchen scraps contain proteins and will cause much more stink in your tank so the tank needs treatment for that.
Safe travels
__________________
God this is so much fun!!!
ewo1
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11-13-2022, 06:39 PM
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#3
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Almost There
Join Date: Aug 2020
Location: Greensboro, NC
Posts: 95
Year: 2008
Coachwork: IC
Chassis: IC CE300
Engine: Maxxforce DT
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Hi David, I am venting a 70 gal grey water tank (sink and urine) with a 3/4” hose and then a 3/4” horizontal pipe at the top of the vertical side wall, just before the roof curvature. The pipe only protubes by 1/4”. Has been working well so far. Using a 3/4” hose made it easy to route in the wall up.
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11-13-2022, 09:41 PM
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#4
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Almost There
Join Date: Sep 2020
Location: Ontario, Canada
Posts: 75
Year: 2004
Coachwork: Thomas Built Freightliner. Allison 2000 tranny
Chassis: Freightliner FS-65 (dognose)
Engine: Mercedes MBE 906 six cylinder diesel
Rated Cap: 35 feet long
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You both have been super helpful. Thanks. I just ordered that cap.
Nice to know even a 3/4 inch hose us adequate.
Is there a treatment you recommend for stinky food waste?
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11-14-2022, 07:03 AM
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#5
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Bus Nut
Join Date: Jul 2019
Location: Suburbs of Winterset, OH
Posts: 802
Year: 2005
Coachwork: Thomas
Chassis: FS65
Engine: Mercedes 6.4L
Rated Cap: just the 2 of us
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I used a cap similar to the photo above. I didn't want to put a hole in my roof so mine vents out the back. I did modify the base a little by creating a small groove in the base to prevent water from accumulating.
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11-14-2022, 09:52 AM
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#6
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Almost There
Join Date: Sep 2020
Location: Ontario, Canada
Posts: 75
Year: 2004
Coachwork: Thomas Built Freightliner. Allison 2000 tranny
Chassis: Freightliner FS-65 (dognose)
Engine: Mercedes MBE 906 six cylinder diesel
Rated Cap: 35 feet long
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Thanks for the description and the pix!
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11-15-2022, 12:33 AM
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#7
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Bus Crazy
Join Date: Jun 2016
Location: Orange County, CA
Posts: 1,362
Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
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And here's what I did:
https://www.skoolie.net/forums/f50/d...tml#post472637
One reason I did it this way was to avoid any roof penetrations: I have 2kW of solar panels up there, so vents wouldn't work too well of they're under the panels. Obviously the main reason to faff about with double vent pipes per tank is to assure an adequate through-flow of fresh air in each waste tank. I've never heard of anyone else doing it this way, but that's typical of much of my conversion. Don't be afraid of doing things differently!
John
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11-15-2022, 08:26 AM
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#8
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Bus Nut
Join Date: Jul 2017
Location: Rapid City, SD
Posts: 993
Year: 2001
Coachwork: Blue Bird
Chassis: CS RE
Engine: ISC 8.3 L 260 hp
Rated Cap: 36
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I am planning on venting my gray tank into my composting toilet enclosure where any stink will be pulled up a powered vent to the roof.
Ted
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11-15-2022, 01:57 PM
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#9
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Bus Nut
Join Date: Dec 2021
Location: Iowa City, IA
Posts: 642
Year: 2006
Chassis: IC CE300 (PB105)
Engine: DT466e @245hp | Allison 3000PTS
Rated Cap: 66
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I would not think you'd need to vent any higher than a couple inches over the tank since it's not a pressurized system? I'd just keep the vent under the bus and away from windows...
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11-15-2022, 04:51 PM
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#10
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Bus Crazy
Join Date: Jul 2021
Location: Southern Oregon
Posts: 1,607
Year: 1996
Coachwork: AmTran (Now Navistar)
Engine: DT444E (7.3L) International
Rated Cap: 31,800 pounds
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Quote:
Originally Posted by Oscar1
Attachment 69169
FYI your kitchen sink is considered black water as kitchen scraps contain proteins and will cause much more stink in your tank so the tank needs treatment for that.
Safe travels
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I've used various recreational systems over the decades ranging from 1/2 a tent and 1/2 the poles and lines with the other half carried by another Marine, though slide in campers, bumper pulls, 5th wheels, and motorhomes. NEVER used any sort of treatment for the GRAY tank and never heard of the concept of kitchen waste being "black" until the last few years. Black water contains fecal matter.
__________________
YouTube: HAMSkoolie WEB: HAMSkoolie.com
We've done so much, for so long, with so little, we now do the impossible, overnight, with nothing. US Marines -- 6531, 3521. . . .Ret ASE brakes & elect. Ret (auto and aviation mech). Extra Class HAM, NAUI/PADI OpenWater diver
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11-15-2022, 04:53 PM
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#11
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Bus Crazy
Join Date: Jul 2021
Location: Southern Oregon
Posts: 1,607
Year: 1996
Coachwork: AmTran (Now Navistar)
Engine: DT444E (7.3L) International
Rated Cap: 31,800 pounds
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Quote:
Originally Posted by Dbacks2k4
I would not think you'd need to vent any higher than a couple inches over the tank since it's not a pressurized system? I'd just keep the vent under the bus and away from windows...
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The reason for venting higher than all fixtures is that a vent below a fixture allows a full tank to then drain out the vent. Mounting the vent higher than all fixtures means that when the tank is full, your sinks will back up rather than (in most places) unlawfully dumping through the vent tube.
__________________
YouTube: HAMSkoolie WEB: HAMSkoolie.com
We've done so much, for so long, with so little, we now do the impossible, overnight, with nothing. US Marines -- 6531, 3521. . . .Ret ASE brakes & elect. Ret (auto and aviation mech). Extra Class HAM, NAUI/PADI OpenWater diver
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11-15-2022, 05:02 PM
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#12
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Bus Crazy
Join Date: Jul 2021
Location: Southern Oregon
Posts: 1,607
Year: 1996
Coachwork: AmTran (Now Navistar)
Engine: DT444E (7.3L) International
Rated Cap: 31,800 pounds
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Quote:
Originally Posted by TJones
I am planning on venting my gray tank into my composting toilet enclosure where any stink will be pulled up a powered vent to the roof.
Ted
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This will vent your gray tank but will not prevent a full tank from then "venting" liquid directly into your poo bucket.
__________________
YouTube: HAMSkoolie WEB: HAMSkoolie.com
We've done so much, for so long, with so little, we now do the impossible, overnight, with nothing. US Marines -- 6531, 3521. . . .Ret ASE brakes & elect. Ret (auto and aviation mech). Extra Class HAM, NAUI/PADI OpenWater diver
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11-15-2022, 05:22 PM
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#13
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Bus Nut
Join Date: Dec 2021
Location: Iowa City, IA
Posts: 642
Year: 2006
Chassis: IC CE300 (PB105)
Engine: DT466e @245hp | Allison 3000PTS
Rated Cap: 66
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Quote:
Originally Posted by HamSkoolie
The reason for venting higher than all fixtures is that a vent below a fixture allows a full tank to then drain out the vent. Mounting the vent higher than all fixtures means that when the tank is full, your sinks will back up rather than (in most places) unlawfully dumping through the vent tube.
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That makes sense. Thanks for the clarification!
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11-15-2022, 08:28 PM
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#14
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Bus Crazy
Join Date: Jan 2020
Location: Fraser Valley British Columbia
Posts: 1,043
Year: 2007
Coachwork: Thomas
Chassis: Freightliner
Engine: C7 Cat
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British Columbia government waste water definition
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11-16-2022, 06:11 AM
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#15
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Almost There
Join Date: Sep 2020
Location: Ontario, Canada
Posts: 75
Year: 2004
Coachwork: Thomas Built Freightliner. Allison 2000 tranny
Chassis: Freightliner FS-65 (dognose)
Engine: Mercedes MBE 906 six cylinder diesel
Rated Cap: 35 feet long
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According to this document from BC, to be black water it must contain feces. But gray water does not include water from a kitchen sink. So water from a kitchen sink appears to be neither gray water nor black water.
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11-16-2022, 12:13 PM
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#16
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Bus Nut
Join Date: Jul 2019
Location: Suburbs of Winterset, OH
Posts: 802
Year: 2005
Coachwork: Thomas
Chassis: FS65
Engine: Mercedes 6.4L
Rated Cap: just the 2 of us
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both of my waste water tanks are tied into one vent, which is mounted high on the bus.
Why are waste tank vents mounted high? Picture a hot, summer day, no breeze, and you want to relax outside under the shade of your awning. Take a deep breath, yuk...you can almost taste the smell.
Is a single vent adequate? I argue that it is, the vent allows water to enter and exit the tank. Water entering the tank is not going to be a significant amount, all at once. Even the toilet is only going to ad about a gallon at a time. And it's highly unlikely that you would be running sinks, toilet and shower water simultaneously.
By far, the biggest change in tank water level is when you empty the tanks. When you do, it's black water first, then the gray. Not at the same time, the gray water rinses out the sewer hose, etc which reduces the smell and makes it a least a little more sanitary (not completely).
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11-21-2022, 08:32 PM
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#17
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Almost There
Join Date: Sep 2020
Location: Ontario, Canada
Posts: 75
Year: 2004
Coachwork: Thomas Built Freightliner. Allison 2000 tranny
Chassis: Freightliner FS-65 (dognose)
Engine: Mercedes MBE 906 six cylinder diesel
Rated Cap: 35 feet long
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FYI, I have installed the gray tank vent. It's not yet hooked up to the tank because I haven't yet bought or installed the tank. But I drilled a hole in the side of the bus above the windows and completed that end of the installation. I've posted a YouTube video about the it:
https://youtu.be/ji3IfM11x-s
(Starts at 23:11)
Apart from a recomendation about the vent cover (thanks, Oscar1) I was not able to find much online about how manage the part where it exits the bus. So I pretty well winged it. If any part of my approach makes you smile (or makes you wince) feel free to share your thoughts so we can all learn.
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11-21-2022, 11:16 PM
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#18
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Bus Nut
Join Date: Jul 2019
Location: Suburbs of Winterset, OH
Posts: 802
Year: 2005
Coachwork: Thomas
Chassis: FS65
Engine: Mercedes 6.4L
Rated Cap: just the 2 of us
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Well done video.
Maybe you should create a path of escape for any water that may accumulate under the gray water tank vent.
My only other question is how all this will fit under whatever interior ceiling/wall covering you will use. Between the barbed fitting and the plastic vent tubing, you may need quite a bit of space. Bend that tubing too much and it will kink.
Only thing that I can think of at this moment would be to get a 1" heater hose with a 90 molded into it. You will still need space, but the chance of kinking the vent hose is reduced.
https://i.ebayimg.com/images/g/M2YAA...Ugk/s-l400.jpg
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11-22-2022, 12:00 AM
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#19
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Bus Crazy
Join Date: Apr 2013
Location: Colorado
Posts: 2,359
Year: 1993
Coachwork: bluebird
Engine: 5.9 Cummins, Allison AT1545
Rated Cap: 2
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i've used 1/2" pex as vent tubing on my bus, and marine fuel tank vents as the exit vent for the tanks. look for a vent that has an elbow on it.
i did not want to put a hole in the roof. i placed the vent high in the driver's side wall away from windows.
12 years since the first one and all works fine. did the same thing with a van last year and used 5/8" clear tubing. easy peezy installs.... works great
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11-22-2022, 06:22 AM
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#20
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Almost There
Join Date: Sep 2020
Location: Ontario, Canada
Posts: 75
Year: 2004
Coachwork: Thomas Built Freightliner. Allison 2000 tranny
Chassis: Freightliner FS-65 (dognose)
Engine: Mercedes MBE 906 six cylinder diesel
Rated Cap: 35 feet long
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My thoughts about hiding it aren't yet fully formed, but the tentative plan is to hide it in a mirrored vanity cabinet. I like the heater hose idea. Thanks.
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