sewer gas odor - trouble shooting, part 2

In my continued quest to find the source of the elusive sewer gas odor in Tatyana I finally have time to conduct a more thorough investigation. One thing I had wanted to do is to check he integrity of the vent connections of the two waste water storage tanks. Unfortunately due to the very compact packaging of the Westfalia design most of the connections can not readily be inspected visually. One prime suspect of the odor the vent tube plumbing system from the two waste water storage tanks on their way to the roof top vent port en route behind the plywood cabinetry. Most of these space are not visible without employing an inspection camera designed to see tight spaces.

While inspection camera recently becomes accessible for consumer most of them are junk except the one that still cost $200 or more. Still I could not justify one for the rare occasional need. I improvised my Microsoft Lifecam Cinema HD webcam hoping it would serve the purpose. One challenge is illumination. Unlike the purpose-made inspection cameras web cams do not have built in light source so using them in a dark space one try to inspect would required the challenge of illuminating the tight space one want to inspect with the camera. I have a solution - used a LED light powered from a USB port. I have an USB hub which allow me to plug in this USB LED and insert the LED into the crevice.

i use electrician's tape to secure the webcam to the end of a steel wire - i can bend the steel wire as needed to reach the camera into the crevice

the webcam provides a maximum of 1280x720 (720p) HD resolution

the webcam is inserted into the crevice behind the plywood cabinetry and the vehicle sheet metal on the driver side at the rear door

It turned out the webcam functions very well in very low ambient light. I was able to perform the inspection without the need of any auxiliary illumination.
black water tank vent tube emerging from the sewer storage tank - the connection is good and tight

grey water tank vent tube emerging from the plywood cabinetry - i could visually inspect the connection to the tank on the other side ant that is good and tight as well

grew water tank (front) vent tube en route towards the roof; the tubing with yellow rings is the furnace hot air supply to the bathroom

this is the connection that I could not inspect before - it is the t-connection in which the grey water tank and black water tank merges into a single vent tube which eventually vents to the roof-top vent port; this shot is taken from the crevice looking up towards the roof

another perspective of the t-connector showing the connections are good and tight; the cable ties secures the connector to the cabinetry to support the weight of the hoses

connections on the black water tank can readily visually inspected

behind the black water tank (black tank on left here) is a small part of the grey water tank (black tank on right here) visible

using a shop vacuum to check for leak

i use duct tape to secure the vacuum cleaner's hose to the waste water vent port on the roof

By using a very powerful shop vacuum cleaner to draw air from the roof top vent, I use a PVC  hose serving as a stethoscope hoping to detect any leak. The challenge is to discern a leak from the air rushing noise caused by the vacuum cleaner. I was looking for a significant change in the sound around a leak.
poor man's stethoscope

By removing the bottom panels of the kitchen cabinets under the sink I was able to check the connections with the PVC stethoscope. All the connections are good.
the black abs pipe is the kitchen sink drain; the small diameter grey hose is the overflow drain tube for the grey water tank; the hoses with the yellow rings are furnace host air supply to the cabin

With my poor man's stethoscope I found no leak in any of the plumbing joints. The inspection camera also found no obvious leak with the venting connections from the two tanks to the roof vent port. These leave the remaining suspects:

1. the u-traps may not be filled by water and allows the sewer gas to escape into the cabin
2. the two sink drain one-way vent valve
3. sewer gas re-enter the cabin from the roof vent through the bath skylight

To eliminate (1) I ensure all three U-traps are filled with water during my monitor period for the next week or so. To eliminate (2) I placed plastic bags onto the two sink drain one-way vent valves. It is my believe while these vent valves may be functioning as designed, they may be the cause of the leak as air pressure change lead them to open momentarily.

For (3) I begin to think is unlikely because: a) the bath skylight has a very tall parameter wall and any sewer gas lingering on the roof surface would have to "hop" this barrier to enter the cabin. I have never smell the odor in the bathroom.

the bath skylight has very high skirt (the white plastic) forming a barrier against sewer gas lingering on the roof

Armed with these new information from the further inspection the next step is to patiently wait for the accumulation of the odor. One problem with isolating the source of the sewer gas odor is the lingering odor in the vehicle. I have found the strongest odor tends to emerge from the crevice between the cabinetry and the vehicle sheet metal on the driver side (but hardly detectable in the under-sink cabinet). In the recent camping trip I left the rear door open for a while to allow the breeze to flush out he accumulated odor in the crevices in the lower part of the vehicle (most of these are underfloor and behind the interior trims and cabinets.

flushing out the odor remnant in the stiff breeze

While the likely suspect is the kitchen sink vent valve one would incline to think the cabinet would have strong odor but it only has a faint smell even in the worst situation. I now think the odor tends to settle to the lowest part of the interior due to the heavier methane gas. The heavier methane accumulates it displaces the lighter air and becomes more concentrated.

Any strong air movement in the cabin disturb this settled gas and being some into the cabin. Hence the elusive sewer gas odor comes and goes and especially noticeable in breezy condition or driving with a window open.

It has been nearly a week now that I have been monitoring the sewer odor and so far there is no increase in level of odor (over the faint residual odor at the crevices at the vehicle rear). This seems to be pointing to the two sink drain vent valves being the source of the leak (whether they are malfunctioning or not given the inherently weak design under dynamic pressure change conditions).

Before my ownership of this camper I had never heard of this drain vent valves. While they are designed to be use in some constrained residential house they are not permitted by code in most juridictions. Reading between the lines on this product page give you some obvious clues to their inherit shortcomings and limitations.

A Few Things About the NAFTA James Cook
A few words is in order on the design of the waste water tank venting system. From my research and inference this venting system is unique to the US version of the James Cook. I infer in the (asymmetrical) collaboration between Westfalia and Airstream the latter serves as the US RV expert to adapt the original European design so it meets the US regulatory and industry SIG (special interest group) including RVIA requirements. In my comparison of the parts diagrams between the European and our NAFTA counterparts all the plumbings for the Airstream (aka NAFTA) version is different from the European version. This include water inlets, connections, fresh water system (short of the faucets), toilet, drain pipes and fittings, hot water heater, and all the waste water system including the gas vent.

With my ownership of the camper of under a year, so far I am less than impressed with all the uniquely NAFTA design and implementations. Sure, many of the contents may be installed in Westfalia factory I infer most are Airstream's "expertly" contributions.

To quote one long time NAFTA James Cook owner - While the NAFTA James Cook based on the European James Cook manufactured by Westfalia, our NAFTA version resulted from the collaboration between Westfalia and Airstream. We ended up with a James Cook with a bunch of junks that Airstream specified or installed on the European version.

These junks that he refers to are:

• Instance that a roof top air conditioner is a must have standard equipment for the US RV market
• With the addition of roof top air condition a generator is required - we ended up with a lousy propane constant RPM generator in place of the spare tire storage; along with it comes the ugly controls
• An LCD TV with integrated DVD player - along comes more cabinet cutout and the roof top antenna
• US style toilet that is much bigger than the European version. The US style toilet necessitated the black water storage tank at the expense of lost storage space.
• A never-works black water tank indicator; I am sure the manufacturer done no testing on the design basically a pair of immersed electrodes that attempt to detect the resistance change of shit-mixture of the black water tank.
• Dubious duplex 115Vac outlet behind the rear door.
• Dubious cable/antenna and land line telephone input jacks - I can just picture the Westfalia engineer must had rolled their eyes at these ridiculous insistence by their US partner.
• A cheesy microwave oven inside a kitchen cabinet
• Instead of a on-demand intelligent gas-fired water heater we have a antiquated Suburban tank style water heater with a continuous pilot light. What's wrong with such design? It's designed to fail catastrophically steel tank requires a consumable anode rod. The pilot light contribute to interior heat when camping in hot climate.
• A huge ugly cutout and flimsy access panel for the Suburban water heater
• Some vehicle has added grab handle on the kitchen cabinet for accessing the upper berth, notwithstanding that Westfalia already provided one on the right side.

In the pictures below is the European cassette toilet. It has integrated flush water storage tank, and a removeable cassette waste water storage tank which you can empty into your home toilet.

 the stowable spout is for filling the flush water tank - in the bag in the foreground are the seat and lid

cassette waste water tank removed for waste disposal at home (or during the trip)