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Author Topic: We NEED tank help!!!  (Read 954 times)
John316
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MCI 1995 DL3, DD S60, Allison B500.




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« on: September 20, 2009, 07:09:53 AM »

We are on the road, and are having surprisingly few issues. One of the more major ones is our black tank smells. It doesn't smell all of the time, just a really strong smell comes up when the toilet gets flushed, when we are driving. I do think it is okay when we are parked.

We have the gray and black tank vented through the same 1.5" vent. I know that we shouldn't need deodorizers but, I am going to need them, if we don't get this issue fixed.

Ideas?

God bless,

John
« Last Edit: September 20, 2009, 07:26:50 AM by John316 » Logged

MCI 1995 DL3. DD S60 with a Allison B500.
Frank @ TX
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« Reply #1 on: September 20, 2009, 07:24:00 AM »

Hi John,
Sometimes the tank smell comes back from the toilet.  But only if we're moving down the hiway. 
I think the inside of the bus is a much lower pressure than the outside when it's in motion.

I also found if the toilet needs to be used on the hiway I open vents in the front and normalize the pressure (in vs out ) and then there is no problem.
Frank
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luvrbus
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« Reply #2 on: September 20, 2009, 07:37:33 AM »

John, did you use P traps on all the fixtures sometimes going down the road the water leaves the traps and it will break the seal causing the smell when the toilet is flushed just make sure the traps have water. 


good luck
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buswarrior
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'75 MC8 8V71 HT740




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« Reply #3 on: September 20, 2009, 07:56:24 AM »

As noted, it is a pressure thing, the toilet is breathing back into the bus when you flush.

Also, as noted, maintaining the stock driver's/defroster venting in the front of the coach, and/or the stock HVAC gives you ways to keep the interior under pressure. Many converted coaches have these openings blocked off during conversion.

Hurtling down the highway, every gap and crack in the sides is sucking air out. Opening the toll window and flushing the toilet will really let you know what was eaten yesterday....

Running the stock HVAC fans will pressurize the coach, all things being closed up, if the intake vents aren't blocked.

Beware that engaging the bathroom fan, or opening the vent in there, will be counter productive, if done prior to flushing.

From all the years on the boards, it seems that those with no smells had a bit of good luck in their vent placement strategy, and have deep p-traps. Shallow ones are easily sucked down just enough to let the wind through in the wrong direction.

Or, they don't use the crapper while under way?

happy coaching!
buswarrior
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BG6
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« Reply #4 on: September 20, 2009, 08:43:30 AM »

Have you tried putting a venturi cap on your tank vents?

Assuming that you are running a real toilet, what's happening is that there is higher pressure in the tanks than inside the coach, and the P trap in the toilet is sloshing open.

It may also be coming through the sink and tub drains, so you want to cap them when moving.

I did my greywater with a "lazy W" trap, which is essentially an S trap and P trap in series, then it drops about a foot to another P trap, then feeds into a sanitary Y with the 3" blackwater pipe trom the toilet, then into a single tank.  Built from PVC pipe and fittings, it cost maybe $15, but gives several "locks" and combats sloshing.
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JohnEd
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« Reply #5 on: September 20, 2009, 09:51:59 AM »

John,

You can beat the problem with air coming back up through the toilet drain.  Fill the toilet with water prior to flushing and when you flush do it so quick that there is still water left in the bottom of the toilet.  You need a lot of water in the toilet and you need to really "stab" the foot pedal.  This only works with "sinkers".....floaters need a yet to be devised strategy.  At least by me.

If you try this with a full of water while you are underway, you can determin if you are getting the back draft or the gas is coming in thru a trap OR an opening in a pipe.  If you get no odor with this test then make sure you have water in the drain traps or cover them before you try the flush.  If the drain and bowl tests still yield odor then you have a leak of gas back into the coach from an opening/crack in a pipe.  A crack should admit gas always when underway but if you get to that point then check every possibility. I fought this problem for months and it turned out to be a "CRACK" in the vent pipe behind the toilet.  It was a problem that "happened" after years of trouble free use.  The odor at flushing was HORRIFIC!!! Tongue Cry Angry

HTH,

John
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Hartley
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« Reply #6 on: September 20, 2009, 11:21:14 AM »

I got one of the vent - sail caps. solved my problem quickly.

I went in circles with vents and traps and still had the problem
while moving. The front end of the bus generates a vaccuum and pulls
air from the inside. That is what we found with a smoke bomb test.

Put the sail on the main vent and never smelled anything after that.

Dave...
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JohnEd
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« Reply #7 on: September 20, 2009, 01:20:48 PM »

THE SMOKE BOMB TEST!  Why didn't I think of that?  Absolutely a superb idea.  You can SEE stink if you use one of those. 

Thank you Dave!
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"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
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akroyaleagle
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« Reply #8 on: September 20, 2009, 02:55:06 PM »

Bus Warrior hit the nail on the head. Close the toll window while the toilet is being used.
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Joe Laird
'78 Eagle
Huron, South Dakota
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