Starting to get more calcium build up on black outer pool tiles
Is standard white vinegar the best way to remove these as also read you can use a pumice stone but worried about getting the tiles scratched
Also is the cause of this due to Ph/chlorine balance?
Thanks for all your help.

I use citric acid mixed with hot water and spray on the stains. Works well on tiles and porcelain.

https://s.lazada.co.th/s.Zdixa6

14 minutes ago, Hummin said:

I use citric acid mixed with hot water and spray on the stains. Works well on tiles and porcelain.

https://s.lazada.co.th/s.Zdixa6

Excellent just bought some thanks
Do you leave it on for 30 minutes or so and do you need to use anything like a non scratch pad to remove it afterwards?

I had some really bad stains in my toilet after leaking for weeks when I was gone, and I used a paint brush and I mixed a thick mix and left it for awhile, repeated and left for another 15 min or so, and it became as good as new.

On tiles in shower 5-10 min and clean off. Just be careful with skin and eyes if you do a strong mix. Glasses and rubber gloves recommended

I

2 hours ago, Hummin said:

I had some really bad stains in my toilet after leaking for weeks when I was gone, and I used a paint brush and I mixed a thick mix and left it for awhile, repeated and left for another 15 min or so, and it became as good as new.

On tiles in shower 5-10 min and clean off. Just be careful with skin and eyes if you do a strong mix. Glasses and rubber gloves recommended

Great thanks I will see how I get on when it arrives 😀

This is leaching out of the grout lines on the coping tiles. Possible re-grout or re-glue soon. Keep using the citric or "ascorbic acid" which is also great for iron stains. Well known in the pool industry for this reason.