Hot tub ring, fc and ozone

[Bruuuce]

Two weeks ago I filled my newly built pool and hot tub. First time owner of both, so it's been a steep learning curve. I did lots of research on this site prior to the completion of construction. This site is amazing. I haven't been to the pool store once and the pool installers thought I was crazy not to get my water tested at the store. I've used my k-2006 test kit like crazy these past two weeks. Thanks for everything!

My pool is pretty good. Levels good, and adding cya as we speak. Water clear.

Questions relate to my hot tub.

I filled my tub with my very sulfur well water. The rotten egg smell went away once I added the chlorine, as expected since my house has a reservoir tank that has chlorine pumped into it to remove the smell. In the hot tub, I got a dark ring that wiped away with a sponge. I think it appeared as soon as I added acid but it might have just been a coincidence. It kept reappearing very 20 minutes or so but I kept taking the sponge to it. Every time the stain got more faint and eventually stopped appearing after maybe 4 or 5 hours. After a party, I had to top up the tub with a couple inches of water and sure enough the ring appeared again. Faint, but it came back. I assume it's metals in the well water but is there anything I can do about this? In the dead of winter, I don't want to be standing out there after a fresh fill, with a sponge worried that this ring is going cause a permanent stain.

I'm using the dichlor, then bleach method. My levels are

Fc - 6
Cc -0.5
Ph - 7.8
Ak - 60 (I'm still getting ph drift so I'm going to lower this tomorrow)
Ch - 200
Cya - I calculate 25 but I could be off by a few. I'll pay better attention next time.
Water looks crystal clear.

My fc seems to dropping close to zero everyday from 6ppm. I'm trying to figure out the cause of that. Not sure if it's bather load or the fact that I didn't decontaminate it on my first fill. My wife and I jump in for about an hour every two-three days. I'm adding 100ml per day of 8.25% bleach and after soaks. Hot tub is covered.

Any thoughts on turning off my clear ray between soaks and turning it on during soaks? Would that help conserve the fc between soaks? Any downside to this?

 

[chem geek]

Since you have a new hot tub I would suggest using Ahh-Some and then do a water change (or if you really want to wait, then do this before your next water change). New tubs have a lot of greases leftover in them and may also have biofilms in piping so you want to clean that all out. Dichlor-then-bleach then becomes a maintenance method to prevent problems in the future. Chlorine alone isn't great at removing biofilm nor grease though superchlorination does oxidize some biofilm, but the strong surfactant products do a much better job of that. Once removed, chlorine can kill bacteria BEFORE they form biofilms so there are no problems.

Do you only have a Clear Ray which I presume to be a UV system and you do not have an ozonator? Ozone will deplete chlorine if you don't use the spa a lot. I suspect your high chlorine demand is from a combination of the tub being new and the fill water which isn't that clean.

 

[Bruuuce]

Thanks for the response!

I will get some ahh some. Are you saying that my fill water isn't clean because it's coming from the well? After I use ahh some and fill with my well, will I still have higher chlorine demand simply because I'm using well water?

It's a clear ray uv system. I thought it was the same as ozone. Oops.

 

[chem geek]

Yes, water from a well may have iron or other chemicals that chlorine will react with, but quite frankly most of the chlorine demand is likely from the spa being new.

Your wife and you for an hour is 2 person-hours of soaking that would normally need (without an ozonator) around 2*3.5 = 7 fluid ounces (207 ml) of 8.25% bleach and you are adding 100 ml so about half of what is likely required. So that may also be part of the problem as well.

 

[Bruuuce]

Thanks again. Adding to your point... when I was re-reading my manual today, regarding the UV system, I noticed my tub is over 500 gal and not 400 gal! I've been much too light on the chlorine calculations.