Toilet siphon sizes
 

My toilet siphon snapped, removed it, took it to several plumbers
merchants; all said it was larger than average at 12".

Average sizes are apparently 8" or 9.5" - plumbers merchants said they
wouldn't work in my cistern.

I'm confused, surely any siphon just sucks the water out of the
cistern and chucks it into the pan? Why wouldn't the 9" one work?

I can understand that it might not throw as much water down the pan
but the plumbers merchants said it would work at all but couldn't
explain why not.

If the siphon was shorter could one not adjust the ball valve a bit
lower?

Eventually found a 10" version with internal overflow - fitted it;
works fine. Why did the plumbers merchants say the others wouldn't
work?
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blackbat /\x/\