On 11/06/2019 12:24, Jim K.. wrote:
DerbyBorn Wrote in message:
of hot water with a dash of washing
powder. Vinegar, perhaps?


Are you sure it is getting a flow through the pipe. It sounds like you have
done what was needed. (Drill seems a bit over the top)


+1 as you've removed the jet, can you check there's a good flow
out the pipe? If not and the pumps working, there's a
leak...

+1.

Often, the root cause is a gelatinous "blob" of fungus/algae/bacteria
inside the body of the jet behind the actual pinhole. This is why
clearing the jet with wire or a micro-drill doesn't always work.

Provided you can remove the jet to get at the backside you can often
pull this gloop out from that side. Sometimes it can be pushed through
with "guitar string" from the jet side but sometimes the geometry is
unfavourable.

Obviously, check that you have a good flow through the disconnected pipe
too.