Mine may be in the same location as yours. I know they are "along that wall". Have you tried putting Bromide tablets in your toilet strainers. I do this on mine and it seems to kill the odor from the seawater when it enters the bowl. We don't have any pump outs anywhere near us but will where we are moving too. I hope to get a pump installed so when I do get odors I can take her offshore and eliminate. Interested in hearing the results of your experiment. I bet the tanks can be cleaned by putting them about 1/3 full and running offshore in 3-5' seas then pumping out. I used to clean my RV tank like this on Louisiana roads.