one week after plaster

[carlos31]

The plaster dust is under control and brushing continues. I am adding bleach by hand, the liquidator is not online yet.

this mornings numbers

ph 7.5
ta 175
fc .8
cc 0
cya 0
ch 225 or 250 or 275?


I am using Taylor K-2006 and testing CH with a 10mL sample. My water looks more pink than red before adding R-0011L then it turns purple when hitting drop 9, more blue-ish after drop 10, and more blue-ish after drop 11, then stays that color. Drops 9,10,11 get me to 225, 250 or 275 CH.

Any advice on how I should read this?

Should I adjust CH up to 300?


In order to get TA down to 70, I intend to keep driving the PH down to 7.0 and let it rise naturally as the plaster cures, but will this process take too long? Should I aerate to drive the PH back up more quickly?


I added bleach to bring fc up to 2.0 just after this test. I need to start adding CYA as soon as I have cleaned and recharged the filter. The pool store CYA is expensive but the big box store CYA from HTH is relatively cheap. (96% CYA, 4% other ingredients)

Is it OK to use the HTH brand or is there a reason to spring for the pool store granules? I would like to use the liquid but its pricey.

thanks

 

[PoolOwnerNumber9]

I would not add any more calcium for the first 30 days. Your level is fine. Have it double checked at the pool store to confirm your readings if you have any doubt.

It is important to avoid a positive SI for the first 30 days to prevent scaling which is especially noticeable on light grey plaster. At a calcium of 275 and an alkalinity of 175 your pH should be 7.2 to achieve a 0.0 SI at 85 F. Just keep your pH balanced for a -0.1 to 0.0 S.I. By keeping your pH at 7.1 to 7.2 your alkalinity should start coming down on its own. As it comes down start raising your pH to compensate. I would also recommend that you keep the Cyanuric level at less than 10 until 15 days after plaster, 20 ppm for day 15 to 30, and after the first 30 days you can raise it to where you want it.

 

[JasonLion]

Well, I disagree with everything PoolOwnerNumber9 said after his first sentence.

Indeed, leave the CH level alone for the first 30 days. The CH test goes till the color stops changing, so 11 drops or 275.

You could aerate, but I wouldn't. During the first three or four weeks the PH can rise very rapidly. If you add extra aeration to that it might rise too quickly and get too high. If you keep a close eye on things you will be fine, but don't risk letting the PH get above 8.0.

Yes, HTH brand CYA is just fine.

Forget about trying to optimize the SI right now, that is impractical. Just keep the PH between 7.0 and 7.8 if at all possible and never let the PH go above 8.0.

You need some CYA in the water so you aren't losing all of your chlorine to sunlight. I suggest you aim for a CYA level of 30 to start and adjust from there.

 

[PoolOwnerNumber9]

Perhaps my post was poorly written, or not clear. So I will try to rewrite it to make it clearer. (Assumes a temp of 85 F.)

The current SI is + 0.3. When there is a lot of plaster dust, and a high SI, there is a risk of scaling and mottling. On a grey plaster pool the scaling and mottling would be especially noticeable. If the pH rose to 7.9 the SI would be +0.7, which would greatly increase the risk of scaling.

My idea was to balance the high Alkalinity with a lower pH. At an Alkalinity of 175 the pH for a 0.0 to +0.3 SI would be 7.2 to 7.5. Keeping the pH at 7.2 to 7.5 would cause the Alkalinity to drop. When the Alkalinity dropped to 135 the pH could be kept at 7.3 to 7.6. When the Alkalinity dropped to 110 the pH could be kept at 7.4 to 7.7.

As long as the pool is brushed and kept clean, a SI of up to +0.3 should not be especially risky. However, I believe that a SI over +0.3 would present a fairly large risk for scaling. I also would recommend that the SI not go negative, which could etch the plaster.

It is/was my understanding that certain chemicals like salt, cyanuric acid and sodium bisulfate should not be used for the first 30 days. On the Cyanuric acid, I may have been misinformed about the need to wait 30 days. However, I think it is best to wait until at least after most of the plaster dust is gone, which should be within the first 7 to10 days.

Hopefully, this is clearer. If you still disagree, that's fine. I just wanted to be sure it wasn't due to my poor writing.

 

[carlos31]

thank you both,

I can keep my CSI in the recommended range, so I am doing so. I just need to keep adding acid every day to bump the PH down. Instead of bumping it from 7.8 to 7.2, I am bumping it 7.6 to 7.4 which requires more frequent testing and smaller adjustments but I don't mind.

The Pool Calculator makes computing the CSI a breeze for us DIYs.

thanks,

 

[carlos31]

I am about 3 weeks in and I feel like I should have a tanker of acid parked in the driveway. To maintain the CSI in the narrow range of 0 to .3 during the initial cure month I add about 44oz of acid in the morning and the evening. My TA has only moved from 140 to 130. I figure I should continue maintaining CSI in the narrow range another couple of weeks. After that, will it be OK to start lowering the ph to 7.0 and aerating so that I can get TA worked down to 70? After I get TA down I would like to add borates to try to lock down the ph.

Does this approach sound reasonable?