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Old 07-13-2013, 08:09 PM   #1
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Black Water Smell

We are having a problem in the RV with Black Water Smell. We have put Cem in both the Potty and in the sinks but we are getting smell. We are camped at a full hook up park and dump every few days and we have run lots of water through. Can anyone Help us with some Ideas??????

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Old 07-13-2013, 08:24 PM   #2
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we have found that adding 2 or 3 gallons of water after dumping helps a lot.

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Old 07-13-2013, 08:28 PM   #3
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Something must be wrong with the sewer ventilation through the roof, is one thought.

I assume that you did not have the problem earlier, it just started. Therefore, if the smell is coming into the coach, there must either be something that is preventing the normal ventilation through the roof vent, or lowering the pressure in the coach versus outside pressure..

Another thought is that you are doing something that is lowering the pressure inside the MH. This could be things like running the fans (the fan in the toilet room, for instance, or constantly running the fantastic fan, etc.), or leaving all the vents and/or windows open. An example, if you need to run the fan in the toilet room, turn it off before flushing, which could cause the fumes to come into the coach versus venting outside. The fumes take the path of least resistance, so if the pressure is lower inside versus outside, the fumes will come into the coach.

You may have a leak in the dump area, which could be getting into the coach as the bin is closed.

You may want to look into a venting system that is better at pulling the fumes through the roof vent. They have options for this at Good Sam Club for instance.
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Old 07-13-2013, 09:25 PM   #4
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Black and Grey water smells can be the same. If you have a W/D make sure the p-trap is full of water; just run the washer. Tedgard01 is accurate in his appraisal. Adding vents to the roof pipes helps disperse odors so they do not get drawn down into your coach.

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We use a different brand but it solved the problem for us.

And periodically instead of just flushing our black water I use one of the high pressure attachments to a hose and stick it down the toilet and blast the scum out. It really helps keep the tank clean and free of odors.
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Old 07-13-2013, 09:34 PM   #5
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My guess would be it is defiantly through the roof vent. Also these smells can be stronger in the heat. But check your roof vent.
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Old 07-13-2013, 09:52 PM   #6
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In addition to checking the vent I add about 5 gals water after dumping (5 flushes of toilet) and I use the Geo Method. No smell in years.

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Old 07-13-2013, 10:34 PM   #7
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Every time we have this problem, running the washer fixes it. The P-trap for the washer evidently empties out just enough so that a direct air path is opened from the gray tank to the coach interior. We run the washer on a short cycle and that takes care of it. It refills the P-trap.

The gray tank can smell just as bad as the black tank.
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Old 07-14-2013, 05:08 AM   #8
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Flush your swanky really well and when you leave the park by 4 bags of ice and put it down the toilet. Drive for a while and find a dump on your way home. It will scrape all the chunky stuff out this alway solves my problem.
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Old 07-14-2013, 07:10 PM   #9
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You did not mention where you smell this odour. If you or a neighbour is leaving your grey water valve open while connected to the park sewer system,the smell outside is inevitable. In that configuration,you are furnishing a vent for the entire park sewer system.The nasty smells enter the sewer hose,continue into the gray water tank,leaving via the roof vent to waft down over you or the neighbour's patio.
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Old 07-14-2013, 07:22 PM   #10
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+1 on the roof venting, but I will elaborate. Sometimes it is not necessarily the vent itself, but the craftsmanship involved in construction. I had a very similar problem. We really didn't notice it until someone would take a shower. In that instance, enough water was going in the tank at once that it was really pushing the gas up through the vents. I ended up buying a Siphon 360 which I can say is a really nice roof vent for $30 and a lot better than the dumb hawk style vents the manufacturers use. That said, upon removal of my old vent, I realized that the vent itself was a 2" PVC pipe up through the roof, but the hole it ran through was about 5" and was not filled in. This resulted in gasses going up the vent, hitting the vent cap, and then coming right back into the coach! a $3 can of spray insulation from home depot filled in the gaps and I replaced the vent cap with the Siphon 360 since I had already purchased it. No more smelly problems!

It looked like you were rolling in a '12 model so figured you might be the first owner, and since you're hooked up to a sewer connection, figured you're pumping plenty of water into your tanks with no concern....and thus pushing that gas out faster than normal.
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Old 07-14-2013, 07:29 PM   #11
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Good advice so far IMHO but since this came on suddenly and you're on FHU, be sure to give your batteries a check. An over cooking battery can be confused with waste tank odor.

Originally Posted by brandonklink View Post
Flush your swanky really well and when you leave the park by 4 bags of ice and put it down the toilet. Drive for a while and find a dump on your way home. It will scrape all the chunky stuff out this alway solves my problem.
We like doing a variation of this frequently too but I make sure to add at least a half tank of fresh water to the black tank before adding the ice so it can reach above just the bottom few inches of the tank and moves around more freely.

Good luck.

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Old 07-15-2013, 07:16 PM   #12
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I put water softener and Dawn in both tanks then filled both tanks with water, let it sit for 24 hours then dumped, no more smells. I am purchasing a new vent for the roof to make sure I get good vent
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Old 07-16-2013, 07:44 AM   #13
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This is a long post, but stick with me here as I expand on my previous post......

I think that generally everybody has given good advice to ensure that you have a clean tank to start with, but if you really think the process through, I think you’ll see it’s most likely a venting issue and not a dirty tank issue. Think about it like this……if you have a half full black and gray tanks, and you park your rig for a couple weeks with a locked door, when you come back your coach isn’t going to smell like a latrine. That is mainly because the tanks are half full of fluid, and the other half full of gases. Without being disturbed, very little is going to happen. New gases will be omitted and slowly leak out the vent, but at such a slow pace you wouldn’t notice it. Now, if you take that same situation of having some nice stinky half full tanks and you decide to take a shower or do a lot of dishes, or anything that is using a lot of water, that water has to go somewhere. That somewhere is obviously into the tanks. As the extra water enters the tanks, it takes up some of the space previously occupied by the gasses in the tank. That gas has to escape or is pushed out of the tank through the vent system, and is forced to do so at a lot faster pace than normal as a large amount of water is flowing in and taking up the space. If the vent is not working properly, or there are gaps in it, the gas is going to escape to wherever it can (path of least resistance). Sometimes that means making it’s way into the coach and creating a smelly situation.

Given that you were at a full hookup site, I would bet that you are using a lot more water than if you did not have a convenient sewer connection to dump into. That would mean water flowing into your holding tanks a lot faster than normal and pushing the gasses out much faster than normal. I would reiterate that in my situation, we never noticed any smell when someone would use the potty or we did a few dishes. When we would notice it was when someone showered and was putting more than a short burst of water into the tank. It was forcing the gases out at a faster pace, they were going up the vent, hitting the top of the vent cap, and then coming back down into the coach via some extra space that was cut into the roof to run the PVC piping through. Pay attention to when the coach starts smelling. Is it fine after someone uses the potty? Can you wash your hands and such in a sink without it stinking? Does it only happen after heavy water usage?

I'm not saying this is for certain your problem, but I would note that regardless of if you start with a sparkling clean tank or not, as soon as you get some sewage in the black tank and some gray water in the other (which can smell just as bad), the tank is going to stink in general. The benefits to periodically cleaning your tanks as suggested should be obvious, but starting with a clean tank isn’t going to make the contents flowing into them smell rosey. As I just noted, don’t be perplexed if the smell is happening when you’re running the sink water or shower and figuring that is going into the gray tank whilst wondering why it smells like sewage. That gray tank water can be just as smelly as the black tank, and often times the vent pipes for the separate tanks end up being joined into one ultimate pipe that comes up through your roof; therefore, the gasses being pushed out of the gray tank can also pull some of the gasses from the black tank with it as it vents out the top.

Another poster who mentioned batteries has a valid point as well, but considering it looked like your rig was a ’12 model I think you can probably rule out corroding coach batteries. I’ve also seen things about stinky washer/dryer connections, and the small venting check valve that is under the kitchen sink; however, given your situation and what’s happening, I’d betting my money it’s your vent on the roof and gases are making their way back into the coach. The only thing I’ve not noticed but assume is that you are indeed closing both your black and gray valves and not leaving one of them open allowing all those sewer gases to come up out of the ground (through your sewer connection) and up through your MH tanks and subsequent tank vents. That would also be the same issue as described above. I’m also assuming that you have water in all of your P-traps under the sinks and shower so that gasses can’t just flow back up through those pipes. Seems obvious, but you never know.

If you think that what I’ve addressed may be your problem, your remedy is to fill in the gap in your roof so the gasses cannot come back into the coach. You may choose to replace your roof vent at that time since you’ll need to remove it anyhow. Whether you replace it or not, you’ll need to get a tube of Dicor 501. You can get it on-line or at your local RV parts store. It’s not cheap, maybe $12 or so for a tube, but you’ll see why you need it. Climb up on your roof, locate your tank vent. Take a putty knife and gently start prying up the old caulking that is covering the seam between the vent and the roof. Take your time and be gently so you don’t screw your roof up. You just need to be able to access the screws that hold your vent down to the roof. Once you have the screws exposed, remove them and gently pry the vent cap away from the roof. I think what you’ll probably see is you have a much larger hole cut in the roof than is necessary for the PVC pipe that is coming up through it. Fill in that gap with some spray insulation that you can pick up at any hardware store. Replace the vent cap, screw it down, and use the Dicor 501 to seal the seam. The Dicor 501 is self leveling, so as you apply it, you’ll see it spread out on its own.

I hope this helps, if not you, someone who might see it in the future while searching. I’m sure I’m not the only one that has/had this problem.
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Old 07-16-2013, 08:42 AM   #14
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There is one probability that hasn't been discussed. Under each sink and at the washer/dryer and perhaps the tub/shower there is a one way air vent which allows air into the waste pipe but not allow air out. These are very cheaply made and prone to leaking and failure. You can replace with a better built version quickly and might solve your problem.

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