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Old 08-19-2022, 12:24 PM   #1
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holding tank locations and access

I am having some trouble with my middle bathroom black tank, it seems to have a strong sewer smell most of the time, much worse than the rear main bath, and the flush system does not work on that tank. Also in that same bath the toilet tends to burp at you when you flush, so Im thinking a tank vent issue. does anyone know how to access that tank in order to check it out. I have a 2019 43 foot cardinal luxury 3700 with front living and rear main bath, with half bath off the kitchen area. do I have to pull the entire underbelly off the trailer to get to it? because i don't know if I'm up for that. my underbelly is all one piece and it would take a whole day just to get it off.
Thanks for any advice !!
Randy
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Old 08-20-2022, 03:36 PM   #2
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Randy, are you sure that tank is getting emptied? Mine bubbles up when flushing when its getting full.
Otherwise, I agree, sounds like a venting problem. Sorry, no advice to give, I have a 3850rl
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Old 08-20-2022, 03:52 PM   #3
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Yes Iím sure. The Rv stays in a permanent space at an Rv park and only gets used on weekends. So never here more than 2 days at a time and ranks get drained and flushed enemy time we leave. I want to fix flush system on this front black tank but canít find access to it from inside trailer. I know tank is directly under toilet because I can look down and see the bottom of tank through the toilet.
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Old 08-20-2022, 07:20 PM   #4
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You're probably going to have to get a toilet cleaner wand and rinse it from the top.
https://www.amazon.com/Camco-Rinser-...23020441&psc=1
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Old 08-21-2022, 08:38 PM   #5
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Double check your cap on the vent where it sticks up on the roof. I have heard where they stuck the cap all the way down on the pipe, effectively closing off the ability to "vent".

Other thing to add, my black tank was giving problems and I thought the valve stuck closed because when i pulled the handle nothing came out.
It turned out when the factory glued the pipe ends to the valve they slobbered so much glue on the fitting it ran into the groove on the valve and kept it from closing all the way.
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Old 08-23-2022, 08:27 AM   #6
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Don’t have any problems draining any of the tanks, they all drain fine, that’s another weird thing, if there were no vent on the black tank I wouldn’t think it would drain well due to airlock. I checked the two vents on the roof right in that area, when I pulled the caps off one vent looks fine and the other one was not there. There wasn’t even a hole cut into the roof. It is just the roof vent screwed down to the roof with no hole or pipe coming through. Do you think that is wheee the vent was supposed to be and they just didn’t put it in?
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Old 08-23-2022, 07:43 PM   #7
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That is very odd, but nothing about RV construction (or lack there of) surprises
me. Have you tried removing the interior panels in the basement? You should be able to see in there some of the piping, tanks, vents.
If they didn't run the pipe up through the roof, that would account for sewer gas smell.
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Old 08-24-2022, 10:23 AM   #8
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So this middle bathroom is not near the basement area. I wonder if they tied the black tank vent into the grey tank vent stack somewhere in the wall and only took that one vent line out through the roof ?? Who knows, I will never find out until I can see the tank and itís plumbing which means I will probably have to drop the entire underbelly.
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Old 08-24-2022, 12:18 PM   #9
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My Cardinal LTD 3600 has a grey galley tank that handles the shower and the kitchen sink.
It doesn't have a vent through the roof. All I have been able to find is the cheater vent under the kitchen sink. It seems hard to believe that would be how they vent the tank.

Do you have any cabinets or closets near that tank that may have a panel that can be removed? There may be a cheater vent that has gone bad and letting the fumes come in. Those vents are cheap and they do go bad.
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Old 08-24-2022, 01:58 PM   #10
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Quote:
Originally Posted by FirstFiver View Post
My Cardinal LTD 3600 has a grey galley tank that handles the shower and the kitchen sink.

It doesn't have a vent through the roof. All I have been able to find is the cheater vent under the kitchen sink. It seems hard to believe that would be how they vent the tank.



Do you have any cabinets or closets near that tank that may have a panel that can be removed? There may be a cheater vent that has gone bad and letting the fumes come in. Those vents are cheap and they do go bad.
Air admittance valves (usually under sink) are mainly used in addition to a roof vent, rarely in place of. But yes, they do go bad and can allow smells to escape. Cheap and easy to replace.
Are you sure your gray and black tanks do not share a roof vent? I have seen many RVs that the waste tank vents plumbing is joined at some point to use one roof vent.
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Old 08-24-2022, 02:46 PM   #11
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The toilet doesn’t happen to be a Dometic 300 ?
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Old 08-24-2022, 09:21 PM   #12
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Originally Posted by NMWildcat View Post
Air admittance valves (usually under sink) are mainly used in addition to a roof vent, rarely in place of. But yes, they do go bad and can allow smells to escape. Cheap and easy to replace.
Are you sure your gray and black tanks do not share a roof vent? I have seen many RVs that the waste tank vents plumbing is joined at some point to use one roof vent.
I can see my galley tank and the black tank vent. The black tank vent goes up the wall and comes out the roof. The galley tank has no where else to vent except that same wall and there is no other vent pipe there. The rest of the galley tank is under the kitchen floor and there is no place a vent can come up in the kitchen. The kitchen sink is in the island.
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Old 08-26-2022, 07:54 AM   #13
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OP, if this is the 1/2 bath tank look for the valve in the vanity sink cabinet.
I couldn't imagine Cardinal piping that vanity sink into another grey tank. They probably would have just piped it into the black tank for convenience.
Try changing that valve and see if the fume situation improves.
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Old 09-01-2022, 08:58 PM   #14
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If your entire system is plastic, you can use Oxyclean to control the smell. It will corrode any metal it comes in contact with. We had a houseboat black tank that wasn't vented. It always smelled. Oxyclean was our friend, but it was an aluminum tank. When we replaced the tank, we put in a vent that works, and haven't had a smell issue since.
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Old 09-06-2022, 01:21 PM   #15
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Quote:
Originally Posted by kr1928 View Post
I am having some trouble with my middle bathroom black tank, it seems to have a strong sewer smell most of the time, much worse than the rear main bath, and the flush system does not work on that tank. Also in that same bath the toilet tends to burp at you when you flush, so Im thinking a tank vent issue. does anyone know how to access that tank in order to check it out. I have a 2019 43 foot cardinal luxury 3700 with front living and rear main bath, with half bath off the kitchen area. do I have to pull the entire underbelly off the trailer to get to it? because i don't know if I'm up for that. my underbelly is all one piece and it would take a whole day just to get it off.
Thanks for any advice !!
Randy
Try using Happy Campers tank treatment after you dump and flush. Also, check that vent stack isnít blocked in some way.
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