What is the best method of elimination to establish where and how my swimming is leaking?

Got any more info? Leak rate, what you've tried so far, pool type (overflow or skimmer), pool age, etc.

If its a skimmer, I would try putting epoxy putty around the skimmer joints, only 99 baht form most DIY stores .

Depends on the size of the leak but if its in the actual pool surface try squirting some betadine the antiseptic which is a dark brown water based liquid near it and watch where the brown coloured water disappears to

First step may be to let the water seep away until it has reached the level of the leak. I investigated two leaking pools in my career and the leak was found both times to be due to submerged lamps ( which didn't stop us digging away for a few days more, insurance was paying). The most likely place for a leak is at the base of the wall I should have thought.

The Betadine idea is a good one, but in larger pools a bit impractical.

You won't like this but I used to find leaks in plastic lined fish ponds using a pendulum. I didn't believe it either but it worked, you'd have to read up on that.

Grab a snorkel and mask and fill a syringe with food colour and go around the outside of the pool and squirt around.

Then fill with epoxy resin

You've done a bucket test right?

Hi!

I've been using this great tips I found using the bucket test.

https://www.swimuniversity.com/how-to-find-and-fix-a-pool-leak/

 

This test will determine if you have an evaporation problem or a real pool leak problem.

The article also shows how to check the pool leak yourself without hiring professionals.

 

If you have evaporation problem then it would be best to use liquid pool covers which are amazing!

They really do the work and prevent rapid evaporation.

Anyways, I usually buy the Ecosavr by Flexible Solution 2-pack liquid pool cover.

 

I hope that helped you! :)

Somebody squirted coloured water into where the walls meet the floor, and also along the bottom step of the pool.
Water was pouring out at quite a rate, in many places.
Once emptied they removed two tiles up, and two tiles from the walls.
Hacked out all the cement, half of it wet, they filled it with an extra strong bonding cement, that seemingly might not crack.