@RDspaguy @waterbear
Thanks a lot for the insightful information! You've clearly got some great understanding of how water and the chemicals work, which is nice to see when Im so lost and it seems like I got a one-off problem no one can give me concrete answers for..
First of all, you are correct. We are using a floater dispenser for tri chlorine as it was included in the "Chlorine chemicals starter pack" from the spa dealer. Something else noteworthy, is that it doesnt include any sort of shock treatment which Ive found strange as it seems to be the core of sanitizing.
At first my theory was exactly as you say, that the chlorine gases stuck under the lid bleaches the parts, but I dropped the theory as the stains doesnt cover the entire surface above the water. It's a very distinct fade from the waterline up. As you say, Its very hard to notice in the picture which is why we didn't stress it too much at first. We got the spa just before winter time, only used it for soaks in the dark of night and didn't notice the stains around the edge of the acrylic. It's very noticeable when theres no water in it, but not too much filled up thankfully. I could get some closer pictures for you tomorrow if you'd like.
The stabilizer description says it binds metal-ions in the water preventing calcium and other minerals from building up from hard water.
I've only got the test strips as that is what the retailers supplied us with, and they claim pretty confidently that it is enough. Obviously this doesnt seem to be the case, and we should probably acquire some more advanced testing tech. If youve got any suggestions, Id be happy to hear! On the strips, the hardness in the new water is actually extremely low/soft after metal-gone and we're slowly building it up microdosing with the "hardness up" from the startkit, trying desperately not to start a second wave of calcium buildup from the new water.. The Ph is in the upper 7's as I took the advice from @RDspaguy and the alkalnity is also a bit on the high side, but if I understand correctly, you use Ph down to adjust the alkalinity as well, so I didnt mess with it to prevent getting a too low Ph.
Funnily enough, the SO managed to order Bromine by a mistake when we were resupplying, and looking up the differences and ability to swap, we decided to try it instead of chlorine this time (with new water, and a full clean of the tub)
The spa does have ozone, but I have not seen anything in the water that could indicate pollution (if its even visible). Probably worth mentioning is that the water has always looked pristine. Very clear and normal chlorine smell levels, and has been comfortable to soak in every time.
All the products we've tried to clean the calcium off with has been on the skimmer cover which is detachable and outside of the spa to not cover the shell or water with anything that could mess with chemical levels or cause soap/foam. I'll definitely get some muriatic acid to try this week. Other than that Im afraid I cant answer your other questions as Ive only got my test strips.. Ph and TA has been within the normal levels on the strips all of the time we've had the spa otherwise.(Ph between 7.2-7.8 and alk between 80-120ppm)
Many thanks again for the in depths answers. Its very appreciated!
