Simply Koi and More Koi

Can anyone help me how to make a Venturi using standard waste pipe? For some reasons, it does not work when I make them, somehow, water come out of the air hole as instead...

Please be specific what type of pipe work to purchase etc.

Thanks in advance

Hi All,
Please can anyone tell me rather I can use smaller pipe (say 40mm) for the uplift instead of 100mm. Also, what size air pump should required, is it the bigger the better? The reason is that I try to put it inside the multi-bay, has anyone tried?

Thanks in advance.

Giggleswick