I could see this helping keep the gases in the sewer instead of venting out of the roof, but all of your grey drains inside the camper have traps of their own. Do you know which drain had the odors?
[font size="3"]I know the theory of the vacuum breaker (VB) vents under the sinks, but I can't quite reconcile what I think I know with my experiences. The breakers should allow air to enter the drain lines but not allow air and gas to exit into the camper. The theory. But on two different campers I've has gas enter the camper when gas getting back into the camper with it connected to the CG sewer. The first, the Rpod, was "fixed" by replacing the faulty VB. It seemed to work, but I never really tested it. The problem was worse in the Pod because of its air tightness.
The second, this CL, had an early problem where the two sinks would burp and explode water all over the place when the gray tank got 1/2 filled from the shower. I thought the roof vent was improperly installed or clogged. I checked the vent stack and it was OK. The RV shop replaced the VB under the kitchen sink and the problem went away. They say they've seen that before. In theory the VB should not have ever let air escape the tank during filling, but maybe it did. If the VB is really letting air escape the gray tank in normal operation I might not ever smell it until I hook up to the CG sewer and leave the gray valve open. That would leave a clear path from sewer to camper, which is what I speculate is happening.
It's a mystery. Maybe you can decode it. I'd love to understand what's really happening.
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[quote timestamp="1413116470" source="/post/4220/thread" author="@charliem"][font size="3"]I know the theory of the vacuum breaker (VB) vents under the sinks, but I can't quite reconcile what I think I know with my experiences. The breakers should allow air to enter the drain lines but not allow air and gas to exit into the camper. The theory. But on two different campers I've has gas enter the camper when gas getting back into the camper with it connected to the CG sewer. The first, the Rpod, was "fixed" by replacing the faulty VB. It seemed to work, but I never really tested it. The problem was worse in the Pod because of its air tightness.
The second, this CL, had an early problem where the two sinks would burp and explode water all over the place when the gray tank got 1/2 filled from the shower. I thought the roof vent was improperly installed or clogged. I checked the vent stack and it was OK. The RV shop replaced the VB under the kitchen sink and the problem went away. They say they've seen that before. In theory the VB should not have ever let air escape the tank during filling, but maybe it did. If the VB is really letting air escape the gray tank in normal operation I might not ever smell it until I hook up to the CG sewer and leave the gray valve open. That would leave a clear path from sewer to camper, which is what I speculate is happening.
It's a mystery. Maybe you can decode it. I'd love to understand what's really happening.
[/font][/quote]That really is a mystery. I hope you mean air admittance valves instead of vacuum breakers though. Vacuum breakers are used on water lines to prevent backflow, while air admittance valves (AAV) are used on sewer lines to allow air to enter the sewer line during negative pressure. If the sinks are bubbling during showers then that would almost certainly point to a problem with your vent since it's a positive pressure problem. If replacing the AAV fixed that problem then I'd be worried that the new one is defective (especially if you're still getting odors from the sewer).
Another thing to consider is whether you use both sinks regularly. I could see that after driving some of the water might slosh out of the trap into the tank and there wouldn't be an air seal anymore. Might want to run the water on both sinks for a second after setting up camp to make sure there's water in the traps.
Here's what I'd do to solve the mystery though: open your grey valve while empty and point a leaf blower at the opening. Then inspect these points:
drains (if they're bubbling then the vent isn't working)
air admittance valves on both sinks (put your hand over the top and feel for airflow, there should NOT be any air coming out of them)
roof vent: there should be a significant amount of air coming out
If you want to kick it up a notch put a smoke bomb in front of the leaf blower :D
[font size="3"]TT,
I take your point on AAV vs VB. I've always called them vacuum breakers 'cause they break the vacuum caused by draining water. However we techies often get our mumble jumbled[/font][font size="3"][/font][font size="3"] so I yield to your superior knowledge. AAV it is. When I originally had the problem on the CL I thought it had to be the roof vent. The vent was clear and I could see water running from the shower if I looked down the pipe with a flashlight. That led me to conclude LL had shoved the vent stack too far into the gray tank, so I called Don at LL and he agreed I should take it to the nearby Camping World for service. CW fixed it, retested it exactly as I had, and proclaimed success. No drain burping problems since even up to full gray tank.
I dig your leaf blower suggestion. I'll give it a try when I get home. That should reveal the culprit. The comment on empty P-traps after travel is valid, but I was able to recreate the problem at home with known full traps. BTW, with your concurrence, I may bypass the smoke bomb for a while :P.
Thanks.
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If you are going to do the leaf blower test, it is of vital importance - and I need to be crystal clear about this point - that you make sure you know which valve is the grey water and which is "other". Vital. Importance. Do not get that even a little bit wrong.
[quote source="/post/4245/thread" timestamp="1413264487" author="@pinstriper"]Do not get that even a little bit wrong.[/quote]There's no such thing as "a little bit wrong" in this context.