New Salt System, algae is recurring regularly

[SunnyOptimism]

The 10mL test will have a +\- 0.5ppm error (Taylor error is basically +\- 1 drop)

However, you had an OCL (overnight chlorine loss) of 2.5ppm. Therefore, proper procedure is to immediately readjust your pool water back up to shock level and hold it there all day. If no one is able to test and adjust during the day, then you could go over the shock level by a few ppm's and then check again in the evening.

Basically you need to maintain shock chlorine levels until your OCL is 1ppm or less. I know it sounds tedious, and it is. Typically, the algae kill rate is high in the beginning and then the process tails off towards the end as your dealing with organic oxidation. It sometimes helps to backwash or clean the filter during this process to remove a lot of the dead algae (think of it as algae corpses rotting in your filter medium and emitting lots of organics into your water). Filter backwashing speeds up the tail end of the process which is the oxidation of organic compounds into volatile chloramines.

[jhk49]

Again, thanks for the info. I have just about run out of R-0871 but I have ordered some. Additionally, I am going out of town next week. So I plan on doing as much as I can this week toward solving the problem .... and, if need be restart in earnest upon my return.

[SunnyOptimism]

If your CYA is still in the low 30's, then use a float with 3" TriChlor tablets in it while you're away. Just make sure that the tablets are 99% trichlor and nothing else. It is perfectly OK to use trichlor with an SWCG. In my 16k gallon pool, three 3" trichlor tablets raise my CYA by ~8ppm and they take a good 10 days to fully dissolve from the float. Using that while you're away can help maintain some FC in your pool so you won't come back to as bad a mess if the algae starts in again. You can raise your FC above shock level before you leave with plain bleach and then throw the float in with a bunch of tabs and you should be good.

[Watermom]

If you are going to put some trichlor in a floater, make sure your pH is in the high 7s to allow some wiggle room for it to drop while you are gone. Trichlor is very acidic.

[SunnyOptimism]

If you are going to put some trichlor in a floater, make sure your pH is in the high 7s to allow some wiggle room for it to drop while you are gone. Trichlor is very acidic.

Hi @Watermom!!

I just wanted to say that I have seen this warning a lot (in various context, not just from you) and I have to say that TriChlor pucks have never had any substantial effect on my pH. Now my pool water normally likes to rise in pH, I have an SWCG and a gunite pool so all those factors probably contribute to trichlor' lack of effect on my pH. Also, trichlor tabs take forever to dissolve in a float for me (typically 10-14 days for three 3" tablets to fully dissolve) so while the water locally around the float might be low pH, my pool water pH barely moves.

Truth be told, I rarely use pucks (only when my CYA needs to be bumped up) so I'm not regularly exposing my pool to trichlor.

Just thought I'd share my thoughts on the subject....

[CarlD]

Hi @Watermom!!

I just wanted to say that I have seen this warning a lot (in various context, not just from you) and I have to say that TriChlor pucks have never had any substantial effect on my pH. Now my pool water normally likes to rise in pH, I have an SWCG and a gunite pool so all those factors probably contribute to trichlor' lack of effect on my pH. Also, trichlor tabs take forever to dissolve in a float for me (typically 10-14 days for three 3" tablets to fully dissolve) so while the water locally around the float might be low pH, my pool water pH barely moves.

Truth be told, I rarely use pucks (only when my CYA needs to be bumped up) so I'm not regularly exposing my pool to trichlor.

Just thought I'd share my thoughts on the subject....

You have other factors acting to raise pH. Many people have a constant rising pH with SWCGs (I don't--don't know why). Many people also have rising pH while their masonry pool is curing. So all your tri-chlor was doing was offsetting some of the upward pressure on pH.

I went away once for 2 weeks (9 or 10 years ago) and left 4 floaters full of Trichlor tabs. When I came back, my CYA went from 30 to 70, my FC was about 5 or 6, but my pH had dropped below the measurable bottom of 6.8. 4 boxes of Borax later I was back in the 7's. At the time, here, there wasn't much discussion of the acidity of Tri-chlor tabs, merely of the additional stabilizer. So I asked the question and the answer came back: Tri-chlor is highly acidic.

[SunnyOptimism]

You have other factors acting to raise pH. Many people have a constant rising pH with SWCGs (I don't--don't know why). Many people also have rising pH while their masonry pool is curing. So all your tri-chlor was doing was offsetting some of the upward pressure on pH.

I went away once for 2 weeks (9 or 10 years ago) and left 4 floaters full of Trichlor tabs. When I came back, my CYA went from 30 to 70, my FC was about 5 or 6, but my pH had dropped below the measurable bottom of 6.8. 4 boxes of Borax later I was back in the 7's. At the time, here, there wasn't much discussion of the acidity of Tri-chlor tabs, merely of the additional stabilizer. So I asked the question and the answer came back: Tri-chlor is highly acidic.

The SWCG on balance is actually a pH neutral process. Initially, during the production of chlorine from salt, the chemical reactions raise the pH. But eventually, when that chlorine oxidizes organics or kills algae, those processes are inherently acidic. So on balance an SWCG pool should see no pH change. @chemgeek has some very extensive posts on the chemistry of the SWCG process.

But yes, trichlor is acidic and I have both borates and other factors that suppress the pH drop from that. I was just commenting because pH dropping from trichlor is not inherently an issue for me and I should be more cognizant to warn others about its acidity.

Wow, that's a crazy pH drop though!!

[FormerBromineUser]

I plan on doing as much as I can this week toward solving the problem .... and, if need be restart in earnest upon my return.

Okay then.... What's your plan? How was your overnight test?