In message , John
Rumm writes
On 09/02/2018 23:00, wrote:
Replacing the cartridge in an early Aqualisa 200, but could not get
the rear o-ring out. Showerdoc is hopelessly optimistic when he says
use a crochet hook. Maybe the design changed a bit later, there's no
way to get anything behind it. The only option I can see is to skewer
it, but my skewering items all failed to get far into the rubbed,
it's stiff stuff. http://i68.tinypic.com/2j31ct0.jpg

Which bit is actually the O ring in that photo? Is is the whiteish bit
at the periphery of the rear "hole"?

Any ideas to get this thing out? Ie what tool could I make?

Some needle nose pliers...

One of the side benefits of a rural occupation is finding the discards
of petty theft in crops or gateways.

One such find was a set of tools possibly connected to the manufacture
of false teeth/dentistry. Double ended with a centre hexagonal finger
grip and choice of tiny knife blades, hooks, points etc.

It is some time since I changed our Aqualisa thermostat but I think the
pointy knife loosened the ring in its slot and one with an angled flat
tip hooked it out.

--
Tim Lamb