25 year old early gravity watersaver. think its a gerber. at the inlaws. I've noticed it year after year at christmas time. flush repeatedly. never get a whirlpool or evidence of good siphon. and plenty of unevacuated matter even after flushing several times.

so I figured, bad seal at the wax ring and replaced it. no dice.

and here's the symptom I discovered by accident that continues to mystify me.

if you tip the handle lightly for 5-10 seconds and let a trickle of water out of the tank into the bowl, and then pull the handle all the way, the thing flushes like a champ every time.

Makes me wish the thing were clear plastic and had tappings to measure vaccuum at several points so I could see what was going on. I just cannot understand how trickling a small bit of water over the weir can make a toilet that won't flush worth a damn form a standing start flush perfectly, but I'm thinking somebody out there might have some idea.

talk amongst yourselves.