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Author Topic: Tank venting  (Read 2396 times)
Tikvah
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« on: September 14, 2013, 05:42:07 AM »

I know this subject has been tackled many times, but let's do it once more.....two questions really.

I recently installed a vent on our black tank, seems to have helped a lot with odor.  Now I've finished my kitchen plumbing and realize that I need a vent in my drain pipes (my shower isn't draining properly).  Should I tie my shower drain pipe to my black tank vent?  Do I need separate vents?  I really don't want another pipe through my roof. 

Secondly, we took a drive and noticed some tank odor in the bus???

Dave
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« Reply #1 on: September 14, 2013, 06:25:19 AM »

Does anyone know how the high end converters get away with tank venting without any holes in the roof?

Dave the answer might help both of us.

Grant
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Grant Goold
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Jerry32
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« Reply #2 on: September 14, 2013, 06:31:12 AM »

When I did mine I tied all the vents to one like a stack vent with just one pipe through the roof. I havn't had any stink problems and has been working for over six years. Jerry
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« Reply #3 on: September 14, 2013, 06:38:02 AM »

I put 2 vents in , 1 black , 1 grey . The smell is from the toilet bowl seal . Hard to keep the seal working       dave
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« Reply #4 on: September 14, 2013, 06:52:41 AM »

You can tie the two vents together and have one exit up high.  You can even use the main drain line as part of the vent line, as long as it is a straight, constantly rising run to the tank (so before any P-traps).  As long as you have a main tank vent you can usually use an air admittance valve to vent a sink or a shower, if tying  the vents together is hard.  The vent is for two purposes, to let air in after water to improve draining, so you vent the drain lines, and to let sewer gases escape, so you vent the tank with a constantly rising line.

Brian
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« Reply #5 on: September 14, 2013, 07:05:13 AM »

   Make sure you put some antifreeze in that little hole at top of bowl. Otherwise, when it dries out, the tank fumes will escape into the coach, especially going down the road with the tank contents sloshing around.
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« Reply #6 on: September 14, 2013, 07:14:11 AM »

Ditto what Brian said.

I ran a black tank vent out the rear wall of the last bay to the rear tire well.  Initially I vented the gray tank but just on top of the tank into the bay not realizing how nasty smelling the gray tank was.  Come to find out the gray tank smells worse than the black tank.  It is nasty.  So I used 1" flexible tubing to go from the top of the gray tank and tap into the black tank vent.  Works great- smell is gone.

Some things to think about -
1.  Not sure why...probably air pressure something or other....but when we are moving down the road we cannot flush the toilet without air blowing back up into the toilet when we flush.  Can be messy.  Only a problem at highway speeds...not a deal killer to us.  I used 2" pipe to vent and that may be part of the problem.  Wifey was the first to figure that out and quickly let us know with a loud scream followed by a mumble of grossed outness.

2.  USE MICROFIBER SCREEN on your vent.  We had problems with poop flies after about a month and Scott Bennett gave us the inside tip on this one.  He gave us some screen that was tight enough to keep fruitflies out and we covered the vent with the screen held in place by a cap that we cut the middle out of.  Worked great.  No more flies.

3. Make sure your graytank vent is wide enough to let as much air in as water outflow.  If not then when you dump your gray tank it can suck the water out of your drain traps.  Then your bus will slowly start to smell like the gray tank until you run the sinks again.  We have a 1.5" drain and the 1" drainhose seems to let enough air in to prevent this.

Wish you the best!

-Sean


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« Reply #7 on: September 14, 2013, 08:37:06 AM »

I put three vents through the roof 1 1/2 inch. Might be overkill for our gray/black tank. One thing to keep in mind is is when you are sitting around outside with you favorite beverage is that you don't want to be smelling it either. I would think not venting it up high you may run the risk of having this happen. I have only smelled our tank when parked. That is when more chemicals go I tank.

John
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John Riddle
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« Reply #8 on: September 14, 2013, 04:32:24 PM »

I ended up putting a vent from the black tank up through the roof and venting all the internal plumbing with one-way valves like these: 
http://t.homedepot.com/p/Oatey-Sure-Vent-1-1-2-in-x-2-in-PVC-Air-Admittance-Valve-39016/100201861/
We've only taken a few trips since installation but no problems or smells in the bus so far.

~ Andy
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akroyaleagle
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« Reply #9 on: September 14, 2013, 06:27:11 PM »

We have one vent.
Tried several different things.
Last one several years ago is a venturi which creates a low pressure area rear of the vent. Works good.

Biggest problem was figuring out do not flush while moving until the drivers toll window is closed.
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Joe Laird
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« Reply #10 on: September 15, 2013, 07:10:22 AM »

we used 2 vents. one black tank, one gray tank. A thought if you don't want to go through the roof... we sent ours out the side up top.

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Lin
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« Reply #11 on: September 15, 2013, 09:32:33 AM »

If the problem you are trying to solve is slow draining from the fixtures, the inline vents work fine.

http://www.amazon.com/Oatey-39012-In-Line-Vent-Black/dp/B000KKSP52
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« Reply #12 on: September 15, 2013, 09:48:27 PM »

we used 2 vents. one black tank, one gray tank. A thought if you don't want to go through the roof... we sent ours out the side up top.
That pretty much what I'll be doing, but with a slight difference.   I don't have any vents going through the roof because there will be solar panels up there.   My gray and poo tanks each have two 2" vents in diagonally opposite corners on their tops, and the front vents of each tank join together.   The poo tank's rear vent exits up through a West Marine louvered hose vent out a blanked-off window on the left side, with the vent's louvers facing forward to force air into the tank(s) while driving.   The gray tank's rear vent goes down to ground level and points back, to help suck air out by venturi effect.   This way as I'm driving the air is circulating through both tanks, and the stinky air is at ground level so it cannot get easily drawn up back into the bus.

Keeping fresh air circulating through the poo tank will help the aerobic bacteria there do their thing, hopefully avoiding the use of nasty chemicals to control odors.

John
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« Reply #13 on: September 16, 2013, 02:59:32 AM »


Negative pressure for me. Don't need tank pressurized when driving. One might get unwanted blow back. LOL

John


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« Reply #14 on: September 16, 2013, 03:12:36 AM »

The idea of venting down into a negative pressure area seems intriguing to me.  Even if just during driving.  If I vent in front of my duals, is that enough?
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Tons of stuff to learn!
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