I have had a class A MH for a couple of years now. The last trip the commode would not hold water after use. I'm referring to pressing the right pedal and filling the commode with water after use.
Evidently the valve isn't closing completely.
Any ideas will be appreciated.
I agree that its probably the seal that the "knife-style" plastic piece slides in. Cut a metal coat hangar and bend one cut end about one inch long in a 90 degree angle. Turn off the water and step on and hold down the flush pedal. Gently run the cut end in the groove all around the seal. You may see tiny bits of TP fall out. Just remember to use your new tool very gently so as not to gouge or tear the rubber seal.