Best Toilet syphon

[FiremanT]

One of our WC syphons has never really delivered a really good flush. I should have sorted ot out when first fitted.Cobblers shoes etc.

I am Gas rather than a plumber, and do don't bathroom work.

What does everyone find is the best syphon for a low level, pneumatic operated, concealed cistern. I cannot remove the shelf above, so space is limited. I suppose I may end up removing the whole cistern.

 

[Bosswhite]

I find a flapper valve solves the problem one can empty the total water capacity of a cistern if needs require.
Other than that a bucket of water !!!