LSI/CSI and water temperature change causing imbalance

[Drd]

This is a new one for me, now when I finally get my numbers where I thought they needed to be to be balanced and now check to see how the overall water condition is, it's way off.

I played around with the calculator it to find it's because of the water temperature. I had input 80 degrees a couple of months ago and I re-checked it is now 55 degrees. To get the numbers I need to get to between -6 to 6 means I need to raise my PH from 7.4 to 7.8 (which I understand will lower the effectiveness of my chlorine) and the TA from 80 to 120 now to get CSI/LSI from -59 to -2. This just gets more mind boggling! Why does the temperature cause my pool to appear in trouble now? And what will it mean to now increase my PH/TA for the winter months? I never realized I would have to make changes in water balancing just chlorine level and maybe less pump run time.

CH 300
CYA 30
Borates 30
Salt 2750

 

[PoolStored]

which I understand will lower the effectiveness of my chlorine
^^ This is not true.

GENERALLY: Allowing the pH to go higher will give you the most control because you can lower it easily later. A higher pH will allow you to also maintain a higher TA without excessive pH drift. Adding calcium can help with CSI, but the impact is fairly small, and it's not easy to remove calcium, especially if your fill water is high in calcium.

In the winter, as the temperature goes down, the PH naturally goes up, resulting in the CSI staying at about the same level it starts with. If you are tracking and adjusting PH, you should allow this natural PH increase instead of "correcting" it.

Can you post a full set of test results?
Do you have a vinyl, plaster, or vinyl pool?
Do you use pool math? If so, login with same UID/password as TFP, go to the gear in the upper right corner on home screen. Scroll to bottom and enable sharing logs with TFP.
Do you use your pool in the winter?

 

[pjt]

How are you testing? (Add this to your signature.)

raise my PH from 7.4

Any pH in the 7s is acceptable. Let your pH drift into the high 7s and your CSI will increase.

TA from 80 to 120

Don't add anything to increase your TA. A TA of 80 is fine. Letting your pH naturally drift up will solve your CSI concern. Aerate if you want to speed up the process.

If you did nothing else and simply let your pH drift up to 7.8, your CSI would be around -0.2, which is just fine.

 

[ajw22]

A low CSI for a few months in the winter will not damage a pool.

As said above, let your pH drift up to 7.8 or even a bit higher, and don't force it down in the winter.

A CSI around -0.6 will be fine for a few months when the water is cold. The CSI will move around as the water temperature changes. Don't try and lock into keeping a CSI number. Use the pH range and the CSI range to keep things in reasonable balance. And if the CSI drops off the bottom of the range for a few weeks nothing bad will happen.

 

[mfifield01]

I'm having the same dilemma. My water temp went from 70 last week to 55 this week. I ended up bumping my CH a little bit to 280. I don't want to go higher, since it will probably rise on it's own next spring. Also, I don't want to raise my TA (currently at 80). My PH tends to rise quickly right now (4 month old plaster). I'll just plan to keep my PH around 7.8-7.9 for the winter. My only concern is when I'm gone for a week at a time. I'll have to bump down to 7.5-7.6 before I leave. If I set it at 7.8, it will probably go into the 8s before I get back.

 

[ajw22]

If I set it at 7.8, it will probably go into the 8s before I get back.

And what problems will that create? Likely none.

 

[Gary Davis]

I was researching for a related thread I just opened, and I was about to jump on the statement that "I need to raise my PH from 7.4 to 7.8 (which I understand will lower the effectiveness of my chlorine) ", but I see @PoolStored already rectified that logical error on the OP's part.

It seems the OP has an outdoor pool, the point being that the pH is "almost" meaningless in terms of chlorine effectiveness, simply because the CYA is negating almost any effect that the pH would have on the chlorine (an indoor pool, sans CYA, would be a different story altogether).

There was one statement by @mfifield01 that I didn't understand, which was "I ended up bumping my CH a little bit to 280. I don't want to go higher, since it will probably rise on it's own next spring", where the CH doesn't generally rise or fall unless the fill water changes it - which - I guess - is what he's saying.

Regarding @ajw22's comment about the pH, it's very interesting how much the pool stores want us to 'chase pH'; but in reality, if you look at what effect the pH has on things, and how much lack of control you have over an equilibrium situation, I'm with him that there's nothing unduly wrong with letting the pH rise to its natural ceiling (at least that's what I think he was implying).

As for whether or not an aggressive CSI will damage a pool in a short period of time, I'm on the fence with that one simply because it's almost certainly true, but also the winter is when the CSI drops into the aggressive range - so in a way it's true but in a way it's not.

BTW, in the OP's signature is 10% HASA liquid chlorine... I didn't know HASA made a 10% solution. Do they? Isn't it 12.5% instead? Mine is.