Sanity Checks on Plaster SWG pH Rise in 2nd Year Pool

[DB-Cooper]

When you add acid, it consumes alkalinity. That creates CO2 which makes the pH lower in the water. Then outgassing of the CO2 (from aeration, not the SWCG) makes the pH rise.

Well my SWG produces hydrogen bubbles which provide some aeration I'd imagine (probably not a significant amount) especially compared to just wind. That said, I expected the acid to bring the alkalinity down immediately, and I'm not seeing that (pH is going down immediately). It seems from the Pool School article and other posts that this takes multiple cycles of ph Down + aeration + pH Down + aeration. Not understanding the chemistry, is the consumption of alkalinity a slower process, it must be to support those statements.

 

[mknauss]

I expected the acid to bring the alkalinity down immediately

It did, but not within the range of accuracy of the test. Effects of Adding Chemicals in Poolmath will provide you how much TA will drop with so much acid added to a pool with a certain TA and pH.

 

[DB-Cooper]

It did, but not within the range of accuracy of the test. Effects of Adding Chemicals in Poolmath will provide you how much TA will drop with so much acid added to a pool with a certain TA and pH.

I guess I'm not following. Poolmath told me to get my TA from 70 to 50, I needed to lower my pH to 7.0 - 7.2. I did this by using Poolmath's calculation of 30 ounces to go from 7.6 to 7.2, and within an hour my pH tests confirmed I was at 7.2. However, TA didn't move. So there must be some lag here which is what the articles tend to indicate. What I don't know is if pool math is suggesting I maintain that for some duration. As stated, I had assumed these were going to be very linear, but I don't understand the chemistry of this alkaline consumption the acid does.

It's my belief that a reduction of TA of 20 as suggested by Poolmath would show up in the accuracy of the test. I'll test again shortly and advise.

I appreciate the education and help here, it's been awesome!

 

[crackers8199]

That also asnwers the question of why I don't go lower. At 7.2 or even 7.5 I start to fall out of the recommended CSI ranges. I don't have enough testing of the impact of pH to TA to say for certain, but using pool math, even if my TA comes down with pH my CSI falls out of range.

this actually leads me to a question i've always had (and i'll let the experts chime in because i'm certainly not one yet)...is it such a horrible thing if you lower the pH enough to get have the CSI slightly out of range on the low end? it's going to drift back up anyway as the pH comes back up naturally, so it's not like you're keeping it at that out of range CSI number for an extended period of time...

am i wrong in that thinking? i'm not saying drop it to like 6.8 and the CSI to -1, but if you drop the pH to 7.2 and the CSI is -0.65 and then is going to be back within range as the pH comes up a day or two later, is that really a horrible thing? genuine question.

 

[mknauss]

Poolmath told me to get my TA from 70 to 50, I needed to lower my pH to 7.0 - 7.2.

That is not specifically to lower that amount of TA. That is the process. It takes multiple additions, with aeration to raise pH in between, to achieve that.

Use Effects of Adding Chemicals. It will give you an approximation on how much your TA will come down based on a specific amount of acid added and your current TA and pH.

 

[mknauss]

is it such a horrible thing if you lower the pH enough to get have the CSI slightly out of range on the low end?

For very short durations, as long as the pH remains in the 7's at all times, it is not an issue.

 

[DB-Cooper]

this actually leads me to a question i've always had (and i'll let the experts chime in because i'm certainly not one yet)...is it such a horrible thing if you lower the pH enough to get have the CSI slightly out of range on the low end? it's going to drift back up anyway as the pH comes back up naturally, so it's not like you're keeping it at that out of range CSI number for an extended period of time...

am i wrong in that thinking? i'm not saying drop it to like 6.8 and the CSI to -1, but if you drop the pH to 7.2 and the CSI is -0.65 and then is going to be back within range as the pH comes up a day or two later, is that really a horrible thing? genuine question.

I'm no expert, but I read many threads on about this and general gist was things are safe for short periods of time. I mean if the acidity gets to a super low level like 4, then you have cause of concern, but it's an issue of super low for short periods of time are low for long periods of time, and that means months/years. I think vinyl is also more susceptible, but low pH can harm plaster of course. Most people consider 7.2 a perfectly fine level, even 7.0. In my case, my pH doesn't stay down long. I just measured and now it's 7.3, but given circulation and that I test in the deep end not too far from where I put acid in it makes sense.

I also noticed all my return jets point up, I can usually see there water path above water. I read they should be down for circulation and to not aerate too much. The waters a bit too cold for me to go adjust them all, but I did adjust the one that I can get access to. That might be another source of pH creep for me.

Long story short, I'm not overly concerned with anything short term. I'm going to be keeping pH at 7.4 - 7.6 for the next few days and measure TA more frequently and try to find any patterns.

During the winter I definitely let pH run higher and didn't use much acid (although I didn't fill the pool much either).

 

[DB-Cooper]

That is not specifically to lower that amount of TA. That is the process. It takes multiple additions, with aeration to raise pH in between, to achieve that.

Use Effects of Adding Chemicals. It will give you an approximation on how much your TA will come down based on a specific amount of acid added and your current TA and pH.

Ok, yeah we're on the same page now, I think I misread one of your earlier comments about a direct correlation. What you said is consistent with what I've read where like 26 ounces of acid is required to lower 10k of water 10 ppm. Considering I'm 3x the size, I need to get a lot of acid (and aeration) going to cycle what sounds like just under a gallon and a half of acid through. I've only got about 45 ounces in today, and pH is now very low, so I'll keep working at it for a while.

That said, I'm still perplexed as my fill water seems to be about 70 TA and that's what my TA has been at despite me adding acid seemingly daily. Something else is maintaining that TA. We've had a lot of pollen and then bugs in the pool recently, but I get those out with nets daily. I did read TA does natrually rise with high pH, so I'm guessing it's just prolonged higher pH throughout the winter.

Given how seldom I measured TA, I don't have a good baseline, so I'll start there and see if I'm making any progress. I don't have enough data to make any conclusions, but will start recording.

 

[mknauss]

I did read TA does natrually rise with high pH

The pH does not cause the TA to rise.

A plaster pool, that is still curing will add carbonate alkalinity to the pool water. The majority of that occurs in the first 28 days or so, but a small amount will continue for a significant time.

 

[twillux]

Just a thought, try mixing your acid first rather than pouring it directly into the pool. I found that the acid would essentially sink the the bottom and have little affect on my pH in a similar situation. Fill a paint bucket with pool water, add acid at suggested amount from Pool Math, stir with a paint stick. Then add to the deep end by your return jets, and I even then agitate the water with my pool brush for a minute as you’re doing. This really changed my pool’s reaction to the acid and the results were much more in line with expectations. Adding acid this way is also easier to handle from a safety standpoint; as soon as you mix it, the fumes are much less concentrated.

 

[mknauss]

Just a thought, try mixing your acid first rather than pouring it directly into the pool. I found that the acid would essentially sink the the bottom and have little affect on my pH in a similar situation. Fill a paint bucket with pool water, add acid at suggested amount from Pool Math, stir with a paint stick. Then add to the deep end by your return jets, and I even then agitate the water with my pool brush for a minute as you’re doing. This really changed my pool’s reaction to the acid and the results were much more in line with expectations. Adding acid this way is also easier to handle from a safety standpoint; as soon as you mix it, the fumes are much less concentrated.

That is unnecessary and increases the risk of spillage and getting the acid on you. Please do not do that. Add the acid directly from the container to the pool, if possible, or if you must use a measuring device, pour the acid into the measuring device over the pool and as close to the pool water as possible. Add the acid in a pencil size stream as close to a pool return as possible with the pump running. Brush the area if necessary after adding the acid.

 

[DB-Cooper]

The pH does not cause the TA to rise.

A plaster pool, that is still curing will add carbonate alkalinity to the pool water. The majority of that occurs in the first 28 days or so, but a small amount will continue for a significant time.

Thanks! I've had some other incidents, including one about two weeks ago where some construction and tile saw action found it's way into the pool and the robot had to go into overtime. I can't imagine that was good for pH or anything else. We've had a lot of storms and brushing reveals some dirt in the areas near where decking can get into the pool (splash pad). It's been a rough couple of months with weather, ice storms, wind, crazy pollen season, some construction/repairs at my house and a large construction project at my neighbor's house.

 

[DB-Cooper]

That is unnecessary and increases the risk of spillage and getting the acid on you. Please do not do that. Add the acid directly from the container to the pool, if possible, or if you must use a measuring device, pour the acid into the measuring device over the pool and as close to the pool water as possible. Add the acid in a pencil size stream as close to a pool return as possible with the pump running. Brush the area if necessary after adding the acid.

I read similarly, I don't have good access to a return due to reverse edge, the only one is in the shallow corner near my swim up bar, and I feel I'm better off going into the deep end. I am probably pouring the acid too quickly, but I do try to agitate the water then use the fountain which dumps significant water right in my dump site for 10 minutes after. I'll slow it down and spread it a bit more.

 

[DB-Cooper]

Day 2 Update:
I tested this morning prior to doing anything (and ended up doing nothing).

pH - 7.47
TA - 80-90
Water Temp - 66
CSI = -0.20

Not sure what to make of that, except maybe since I had been testing shortly after adding acid, my TA readings from before were low? So I guess my TA is high which could be causing the higher creep, possibly a result of not adding enough acid through the winter.

Outside of just keeping my acid lower to get more acid through it (I'll shoot for 7.4 - 7.8) and maybe trying to accelerate pH rise with more aeration, anything else I can do? I think this is going to take several weeks.

Thanks for the help.

 

[mknauss]

I agree, nothing to do.

Just manage the pH. No reason to focus on TA. It will balance out as you manage the pH.

 

[DB-Cooper]

I agree, nothing to do.

Just manage the pH. No reason to focus on TA. It will balance out as you manage the pH.

Thanks. Learning a lot here, so will stay the course with my plan. My guess is the TA has increased due to some construction debris that hit the water. Tile saw dust, etc. My CSI is in check, will just focus on that, but will come back to report updates weekly.

Thanks again

 

[mguzzy]

Hi DB.. kind of late to the discussion but wanted to add a few observations.. If you do nothing to adjust your pH, where does it settle? Sounds like if you adding MA daily, its hard to figure that. I find that if I know where I am on the high end, it gives me a better idea of how its buffering. Also you said you are running your water feature/spill over gizmos 10 min a day. What happens if you don't run them but once a week? Less aeration, less pH rise. I flush my waterfall once a week and that seems sufficient. And have you considered borates to help with the pH rise?
construction debris.. ugh.. that is always the bane of crazy pool chem

 

[DB-Cooper]

Hi DB.. kind of late to the discussion but wanted to add a few observations.. If you do nothing to adjust your pH, where does it settle? Sounds like if you adding MA daily, its hard to figure that. I find that if I know where I am on the high end, it gives me a better idea of how its buffering. Also you said you are running your water feature/spill over gizmos 10 min a day. What happens if you don't run them but once a week? Less aeration, less pH rise. I flush my waterfall once a week and that seems sufficient. And have you considered borates to help with the pH rise?
construction debris.. ugh.. that is always the bane of crazy pool chem

I've never really let it get to high, I think 8.28 is the highest. I was on vacation and we had a lot of wind. Maybe next down season (when I'm not chlorinating) I can let it go for a week and see.

On the fountains, yes in fact two weeks ago I didn't run them for an entire week as I was investigating whether I had a leak since there was always water near the bowl. It turned out my valve was just open too much and water was slightly exceeding the water path causing it to run underneath the bowl. Regardless, I didn't witness any difference during this week.

I've no considered borates, now that the pool is getting more and more acid, we'll see if it comes down on its own. Considering the rest of the my levels, if my TA gets too low, my CSI becomes a bit sketchy to where I don't have a wide pH range to play with. It would be interesting to see though if the lower TA would help reduce the amount and frequency of acid needed.

Today again was so windy, the pool was completely rippling from the wind. 15-25 mph sustained winds, and again no shelter from that. Even when the city is basically wind free, I'm higher on an exposed canyon and we still get gentle and constant 6 mph wind which is great for keeping a cool breeze and bugs at bay, but I'm imagining that is providing a lot of aeration as I'm getting effectively swells of 1-3".

 

[DB-Cooper]

After almost two weeks of running pH down to 7.4 every couple/few days, my TA is now 50-60, so will be letting it run up passed 7.8 now and see how fast it rises.

 

[cowboycasey]

Nicely done