replying to KOS, Lev L. John wrote:
A level toilet matters to proper flushimg
An off level toilet can cause the water to slosh side to side, making a poor
siphon. you want that vortex to go straight down to make a.strong siphon
through the trap and out. Those drain holes under the rim are angled to induce
the swirling vortex motion. unlevel units will set that vortex of water
rocking side to side when you flush, causing it to enter the trap more slowly
and making a weak siphon.

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