CH increase?

[rinaldok]

Hey folks, would love to get your input on this one.

Disclaimer: The CH test is my kryptonite. However I don't think I'm crazy on this.

My CH has somewhat suddenly increased and I'm not sure why. My autofiller is on a softened line, so it's not the fill water. We haven't had any rain and there's no other water sources that would be getting into the pool.

I've been about 320-340 consistently, but I just tested (5 times) and I'm coming out with 375-400. Now, I was PLANNING to bump the CH up to around 400, but the past couple weeks I've been focused on my TA.

I have been working to get my TA down to around 70. I'm hoping that will help with my constant high pH, and I also plan on adding borates this year. For the past couple weeks, every couple of days I will drop the pH to 7 and then run the pump and aerator until the pH gets back to around 7.6. Then I'll test the TA again a day or two later and repeat.

Over the past couple weeks I've added 2.5 - 3 gallons of MA total.

Could the MA and pH cycling have any contribution to CH climbing?

 

[Richard320]

Plug your numbers into poolmath and see what the CSI is, especially right after you add acid. You could be very negative and leaching Calcium out of the plaster, or maybe dissolving scale. Your only choices are fill water or the pool itself, and softened water shoudn't have any Calcium.

 

[rinaldok]

I thought it might be something along those lines.

My logs are in my profile, but I haven't been logging immediately after the acid adds.

If I take my existing levels and drop the pH to 7, the CSI does drop down to -0.69, which of course is not good, but I assumed this was expected with a drastic pH drop and also as long as it was short-lived wouldn't be too dangerous. That's one reason why I was waiting a 2-3 days between treatments, so that pH/CSI would be back in the normal ranges for a couple days before I hit it again with acid.

Is there something I should be doing different here, or is this an expected side effect of the process?

 

[Richard320]

I thought it might be something along those lines.

My logs are in my profile, but I haven't been logging immediately after the acid adds.

If I take my existing levels and drop the pH to 7, the CSI does drop down to -0.69, which of course is not good, but I assumed this was expected with a drastic pH drop and also as long as it was short-lived wouldn't be too dangerous. That's one reason why I was waiting a 2-3 days between treatments, so that pH/CSI would be back in the normal ranges for a couple days before I hit it again with acid.

Is there something I should be doing different here, or is this an expected side effect of the process?

Yes. Leave TA where it is and only add acid when pH needs adjusting. It will bring down the TA over time.

You don't want to etch the plaster or eventually the bonds will weaken and you'll start brushing your pebbles out of the walls.

 

[rinaldok]

Yes. Leave TA where it is and only add acid when pH needs adjusting. It will bring down the TA over time.

You don't want to etch the plaster or eventually the bonds will weaken and you'll start brushing your pebbles out of the walls.

Alright, thanks for the help.

I was following the path of "get the TA to around 70 before adding borates" but I guess I was being too aggressive? Putting my target TA into PoolMath just said lower the pH to 7.0-7.2 and aerate to bring pH back up. I guess I should have paid more attention to the CSI changes of that course of action.

My *intent* was to get to the following numbers for this season:

pH: 7.8
FC: 6
CYA: 80
CH: 400
TA: 70
Salt: 3000
Bor: 40

That would have put me in a nice CSI range of -0.2 -- -0.1 as the water temperature changes. Over the winter when the water temperature is colder I figured I would keep the pH around 8.2 to keep the CSI around -0.02.

Maybe I'm trying to overengineer it.

 

[Richard320]

A tip: plug your numbers into poolmath and get your acid dose, then scroll down to Effects Of Adding Chemicals and plug that in. It will tell you how much the TA will drop with that acid dose. Ignore what it says there about pH -- it's only correct within a very narrow set of parameters. But the TA reduction will be right. You'll see that you are making progress, just not as fast as you'd like.

 

[rinaldok]

A tip: plug your numbers into poolmath and get your acid dose, then scroll down to Effects Of Adding Chemicals and plug that in. It will tell you how much the TA will drop with that acid dose. Ignore what it says there about pH -- it's only correct within a very narrow set of parameters. But the TA reduction will be right. You'll see that you are making progress, just not as fast as you'd like.

Geez, I hadn't gotten into that part of the app before. I'd used it for SWG calculations. That's very helpful, thank you for your advice.