A few days ago, my wife mentioned the black tank burped when she flushed and i said it must be full.
drained it and it was not full, but i let the sleeping dog lie a few more days.
this morning went to flush and BUUUUUURRRRRPPP it went, followed by a splash upon the floor.
good thing it was only #1 and water.
i thought this is weird. i go out and flush the tank real good( i have two tornadoes, one at each end of tank) and thought for sure it was good.
went back in and filled toilet and did a test flush....BUUUUUURRRRP
got my trusty VENT snake 1/4" water hose blaster and climbed up top. removed the vent cap and took a look down the hole, YEP vent was clogged.
took us about an hr to get it all flushed out after i broke the blockage of what looked like a wasp nest or maybe ........TP
moral of the story...make sure the bowl is full of water when you flush..
my vent pipe for some reason extends down into the the black tank about 5 "...i know not why, but it is what it is because to fix it , is not going to be a fun day . and its right in the flow pattern of the toilet pipe..WHY why did they do that
so we had a good laugh this morning