On Fri, 2 Oct 2020 10:09:00 +0100, The Natural Philosopher wrote:

I hate to say it, but if its a hard water area, you may have massive
scaling in the U bend.

It's a new pan, think it would have to be a *very* hard water area to
get enough scale/urea buildup to significantly affect the flush in
less than a year.

Of course with the standards of plumbing work show recently plumber
could well have installed new pan onto partially blocked by scale old
pipe without removing scale first...

--
Cheers
Dave.