[ronrai]

What causes low water level in toilet bowl. The bowl will will fill to normal level when flushed, the 30 minutes later is is very low.

[ballengerb1]

Tom, Speedball1, can give you an explanation regarding defective china. It can also be caused by a clogged vent stack that siphons water down the drain. If it is a clogged vent it would drain at different rates almost every time. A defective china would drain identically each time.