/diy/ - Do It Yourself

>>2547071
They did, and still do..."washdown" flush toilets usually have larger holes than the siphon type toilets you posted.
The washdown type uses a large amount of water dumped quickly to move waste and a bigger hole helps, but the tradeoff is that they dont do asxwell as removing stuck on waste and can allow sewer gas to get in, theyre also noisy and often need multiple flushes to get clean.
Siphon type has the benefit of an S shaped trap that helps create a siphoning action when flushed, that actually sucks the waste out. It's quieter and moves the water faster and for a longer time and is optimized to wash off waste that sticks to the bowl. Because of the siphon lock in that trap it also minimizes the chance of sewer gas coming into the space.
Especially with water conservation measures the siphon system has become more favored in many places, but picrel is a washdown toilet you can get now, note the large hole.