Drinking the chemicals certainly isn't good for them. Some animals will drink water from anywhere but their water bowl! Can you cover the pool when not in use?
Animals ofter prefer running water- it may be an idea to get a animal water fountain- this is made to encourage animals to drink, or even get a small paddling pool with fresh water in it- and see if they will drink out of this. I think you should try a few options and see if you can tempt them away from the pool!
The grass is likely to die with any urine on it. You can actually buy something called dogrocks which will help this problem IF you can get them do drink from a bowl!! They may actually prefer the water with a dog rock in it too.
Try this website.
I hope my answer helps and you can manage to tempt your pets away from the pool! Good luck!
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