On 02/10/2020 03:21, Paul wrote:
One thing to do, is compare your recollection of "how well"
the toilet used to flush years ago (just flushing water, look
at swirl pattern and velocity), versus today. If the bowl
drains slightly slower than it used to, with nothing but
water present, you have to figure out why.

We only took the building on a few years ago and there was no WC installed.
The underground plumbing in the yard is only around 5 years old.

The reason I feel like there needs to be more drop is that the flush is
quite slow to drain when it is just water. But as has been pointed out
that would make no difference to a blockage at the U bend.

Perhaps there's an impediment elsewhere in the pipework or the loo is
just poorly designed.

I need to inspect more of the pipe internals. Joy.