The Air Valve on my 5'er is in under the bath sink and it is fine and free. The bleach killed the bacteria that remained after the gray tank was dumped and also cleaned the tank level probes. Again, have had zero problems with the gray tanks since last fall. This latest issue was a critter that died, I just thought it was gray tank issues again. I haven't opened things up yet to see what it was and I probably won't. I have crawled underneath and looked for points that something could get in with no success, but we all know little critters can be very creative.