Unlike many of the hilarious stories on this forum thread, this one is true. I hope I'm posting this in the right place!
Shortly after we bought our motorhome, we went on a 4 day trip to "kick the tires" and see what happened. We arrived, set up camp and had a great time. We cooked dinner, did dishes, took showers, all the usual. After a few days I noticed that the shower wasn't draining properly - oh, oh!
We went out to the local store and got some drain cleaner and a plunger - we were loaded! Nothing worked. Oh boy - hey! Hon, go out and drain the grey water tank - maybe that's it! He did and it didn't help.
Hmm - we sopped out the water from the shower pan (thankfully it's several inches deep). We avoided the shower but the water rose again. Where was it coming from???? At my wits end and getting ready to leave, we drained the black and grey water tanks and guess what? The water was gone! What happened??? I had hubby show me what he had drained. He showed me - the tank closest to the back of the RV has a grey handle - he figured it was closest to the toilet and it would be the black water tank so he had emptied the tank with the black handle (to him - the grey water tank because it was closer to the front of the RV (by about 1 foot). I said - Hello! - Black handle = black water ---- Grey handle = Grey water.
For a man with a masters degree poor hubby has no intuitive ability - he tends to overthink the problem! We still laugh about it.