David Wilson explained :
I am looking for 2 diaphragms for a Hailea ACO 9903 airpump. The only thing
is, when I search online I would be cheaper buying a new pump from my local
pet shop than buying a couple of rubber diaphragms online. How do the expect
to do business when 2 little rubber diaphragms cost £5 and they want £6 post
and packing.

I once managed to repair a diaphragm pump by using a bit cut from a
truck tyre inner tube. Much larger that your pump, but similar idea.
Could you use a section of rubber cut from an old bike inner tube?

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk