i have been cleaning my black water tank with every known product and still get smell. i decided today to remove the model 300 rv toilet and check the seal. I could not believe what I found. When i took the toilet outside and tilted it, stinky, gross waste water came out the back. Apparently there is an internal leak problem and waste water collects inside the toilet. very disapointing and spent untold hours cleaning the tank and expense of differant problems thinking it was a black water tank problem. Is this a known problem with the model 300? If so, is there a program in place to replace them? I dont have wall clearance for a model 310 or 320. Thank you, Jo Ann Miller