Mine quit in our 3121. Checked the vaccum break under the sink and all ok. Pulled the nozzle out of the tank, and broke down toilet paper had managed to get all the way through the holes and dry into a plug. First time that had ever happened to any black flush nozzle. After that, I never let the tank get as full as I did that time.
On the vacuum break, I usually ditch those and put one at the inlet, provided it's in a wet bay or outside. Also use a designated hose. Code requires them to be mounted above the toilet which is why you find them under the sink a lot of times. Almost every one I've had has leaked, which is not cool if you don't catch it. Our mobile scout was in the wall and leaked, our Tiffin was under the bathroom sink, and leaked, the one in our Silverback was under the sink, and leaked. So, usually that's the first item to be cut out of the system for us.
John and Rebecca Dickson
Emma-7 / Little John-5 / Iva-1
Full Timing Again, Rev B
2013 Ford F-350 Lariat CC LB PSD
2015 SOB TT - With OC's Awning Poles (#8)
At least in Heaven, RVs will be perfect, and I won't have to keep fixing them.