1.5 Years into New Plaster - PH Still Rising related to Cracks?

[Hosertx]

I've been struggling with my pool chemistry since I re-plastered my pool in February of 2017 with Quartzscapes after purchasing my home. 1.5 years later, my PH continues to rise by 0.2 ppm per day. So I add acid every other day expecting that soon, my plaster would eventually fully cure. No luck. Per advice in TFP, I've allowed my Alkalinity to drop to 50, and then 40, and then 30 to no avail. I've even tried to increase the alkalinity above 80, but PH continues to rise and alkalinity eventually drops. My calcium hardness is really high at 1,100. I have not really tracked whether the CH has been increasing over time. As I researched TFP, I saw a few posts that indicated that a bad plaster job could cause high amounts of Calcium to be released and PH to continue to rise beyond a year. As I looked at the pool plaster closely, I do notice some "grazing" or cracking in sections of the pool. The good news is that, with the TFP process, my pool water is crystal clear, with no calcium deposits, no cloudiness, and no algae issues since i've owned the pool. Aside from having to buy and pour gallons and gallons of acid (1 gallon per week), I've got no complaints.

Questions: 1) Could the high calcium be a source of my rising PH, and would refilling the pool to get calcium back down stabilize the PH? 2) Are pool grazing/cracks an indication that pool could still be leaking calcium?

08/11/2018

Pool gallons: 14,985
FC: 6 (a little high)
PH: 7.6
TA: 30
CH: 1100
CYA: 30
Temp: 86
CSI: -0.02
Kit: Taylor K-2006

 

[JoyfulNoise]

What is the TA/CH of your fill water?

 

[Hosertx]

Fill Water:
TA: 50
CH: 60

 

[Jimrahbe]

H,

Do you constantly run your spa spillover or other water features that can cause aeration??

We don't really recommend that you let your TA drop below 50...

Are you trying to keep your pH at 7.2, or allowing it to increase above 7.8 before knocking it down.. When you lower your pH what level do you shoot for?

I'm not sure I've seen others from Austin with such high CH...

Thanks,

Jim R.

 

[JoyfulNoise]

Two points to make -

1. CH has nothing to do with pH and the level of calcium ions in the water has no bearing on the pH.

2. The source of calcium entering your water can affect pH.

With fill water so low and your plaster only being 1.5 years old, I don’t see how it is possible at all that it would be at 1100ppm CH. My fill water has a CH of 180-200ppm and it took 5 years with over 90” annual evaporation rates to reach 1500ppm.

Are you chlorinating your pool with cal-hypo?

 

[ctrav]

Interesting post...looking forward to see what happens.

 

[Hosertx]

Thanks Team. Answers to your questions:

Do you constantly run your spa spillover or other water features that can cause aeration?? No, only for 2 hours and when we are using the pool.

Are you trying to keep your pH at 7.2, or allowing it to increase above 7.8 before knocking it down.. When you lower your pH what level do you shoot for? When it gets above 7.8, i knock it down to 7.2. Creeps up to 8.0 in 3-4 days

Are you chlorinating your pool with cal-hypo? Use HDX Germicidal Bleach from Home Depot. Water does taste a bit salty.

With fill water so low and your plaster only being 1.5 years old, I don’t see how it is possible at all that it would be at 1100ppm CH. Yes, that's why i'm wondering if my plaster was not mixed correctly and the curing had something to do with it. The only evidence of bad plaster I see is the grazing and un-uniform color distribution in the plaster. I also wondered if my CH reagents or my technique are bad, but the "guess" strips tell me my CH is also above 1000+ (and that my PH is 0.5 -1.0 below where my taylor tests)

Also realizing my CH reagents are all expired. Ordering new ones on amazon now.

 

[JoyfulNoise]

How often and how much bleach are you adding to your pool?

Your CYA iscreally much too low for Austin, TX and so that makes me think that you must be adding quite a bit of bleach daily. Usually in TX we see CYA levels at the higher end of the recommended range, typically 50-60ppm.

 

[Hosertx]

Yes, adding 1/2 gallon of bleach daily (give or take). I'm been paranoid about keeping CYA low, so that I have room to use pucks when I travel for vacation or business. Good suggestion, I'll raise it.

 

[JoyfulNoise]

That’s about 3.3ppm/day in your pool using 8.25% LC which is not at a worrisome level but is definitely on the high end. Typical daily loss is 2-4ppm depending on bather load. As a comparison, I have an SWG pool and I keep my CYA high at 80-90ppm so my loss rate is about 1ppm/day.

Bleach adds salt and excess caustic (NaOH) to your pool water. If used heavily, you can drive up pH with it along with any sources of aeration. Dropping your pH to 7.2 is both unnecessary and not good for your plaster as your low TA coupled with low pH will make your water very aggressive towards plaster. Targeting a pH of 7.6 and waiting for your pH to get to 7.8 before dosing again will minimize acid use. You should also consider draining some of your pool water when the weather cools. A 50% drain would bring your CH levels down and then you can start tracking your CH more frequently to see if plaster emission is an issue.

Surface cracks in plaster (shrinkage cracks) are not uncommon. Typically they’re most noticeable when you drain a pool but otherwise the water hides them. Color variations (mottling) have more to do with installation, troweling work and plaster makeup.

 

[Hosertx]

Thanks Matt. Should I raise my TA to at least 50?

 

[ajw22]

Target your PH at the high end of the range 7.8. When PH gets to 8 lower it no lower then 7.6. Smaller doses of MA more often keeping your PH on the high side will use less MA.

Taking your PH down to 7.2 is eating a lot of your MA and most of the rate of the PH rise is between 7.2 and 7.6.

 

[JoyfulNoise]

If you raise the CYA to 50ppm then the cyanurate portion of the TA will go from 10ppm to 15ppm, roughly speaking. So you could add about 15ppm to the TA using baking soda or just wait for it to naturally drift up. Up to you.

 

[Hosertx]

Thanks everyone. I'll report back with results in a few weeks.

 

[spoonman]

Couple of thoughts here..

The crew plastering the pool could have used calcium as an additive when setting up the plaster. Someone more qualified than me may be able to comment on how much that could affect CH in the water.

My pool also had a CH of ~1500 after 18 months. I attributed this to a combination of fill water (high CH in the desert) and possibly CH from the plaster job. Can’t say for sure.

Coincidentally, my pool has also had a tremendous thirst for acid despite playing with the TA, making changes in dosing (negligible difference on my pool), etc.

I never did find a way to slow down my pH rise without going to extremes like covering the pool 24/7. For this reason I decided to automate acid delivery with a Stenner pump. I used to be always behind the curve on pH, finding it was more often than not into the 8’s after just a couple days.

Automation of acid is tied with a pool cleaner as the best thing I’ve done to the pool. I seriously feel like I’ve won a battle of wits with the pool. Now my pH is locked at 7.6 and I just look back and laugh. This is a great option if you can’t find another way to control pH rise.