Recommended Chemical Levels for Hydrazzo Finish

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DougS78

Well-known member
Apr 13, 2022
47
Indiana
Pool Size
25000
Surface
Plaster
Chlorine
Liquid Chlorine
I am in my first year of running this pool and spa (finished very late last fall) and still trying to get the hang of it. I am using the Taylor K-2006C test kit.

I have done pretty well keeping the water clear with liquid chlorine every few days.

What I'm noticing is that my PH creeps up every test despite adding Muratic. Almost always above 8.0 (highest test result) on each weekly test. I have done the Acid Demand test and get something like 3-4 drops in the pool to lower to 7.6. The number of drops for the spa is typically more like 12 or more. My question is why this might be and what the values are I am shooting for? I have typically used the values on the Pool Math Calculator, but not sure if those targets vary for hydrazzo.

Today's results
Pool:
Ph 8.0+ (acid demand = 4 drops)
TA = 180
CH = 300
FC = 0.2 (before I added a gallon of chlorine)

Spa:
Ph = 8.0+ (acid demand 12 drops)
TA = 370
CH = 325
FC = 0.2 (before adding 50 oz chlorine)

Any recommendations appreciated!

PS: This is a perimeter overflow pool, which we run some times but not others. Spa is mostly run without the aerated jets.
 
I have had Hydrazoo finish for over 20 years. There is no difference in Hydrazoo from other palster pools.

Keep your pH in the 7's and your CSI between -0.1 and +0.3,

Your TA of 180 is causing your quicker pH rise. My TA is 60-70.

What is the pH and TA of your fill water?

www.troublefreepool.com

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.
www.troublefreepool.com www.troublefreepool.com
 
Thank you both for the help. I see the link you shared @mknauss, but these numbers are lower than what the recommendations are on the Pool Math Calculator so I wasn't sure which to follow.

It does appear my TA is quite a lot higher than those on the link. So it sounds like I need to continue adding a significant amount of acid to continuously lower it to 7.0?

My understanding was that hydrazzo curing would raise ph, but at nearly a year I thought that would be mostly over. Did you find this AJW22?

Good question about PH and TA of fill water. I will test this and see.
 
The Poolmath app has the full range from minimum to target. Same as the link I sent.

Be sure you have the correct settings in the app.
 
DougS78 said:
My understanding was that hydrazzo curing would raise ph, but at nearly a year I thought that would be mostly over. Did you find this AJW22?
Click to expand...

Your high TA is contributing more to your pH rise then any plaster curing.

I need to add about 32 ozs of 31% MA to the pool weekly. Every pool is different. Your pH is likely to never be stable. It is a question of how rapidly the pH rises from about 7.6 to 8.

How much does your spa spillover run? Water featrues create aeration which cause pH to rise.
 
Ahh, Ok, that make sense. I do not think I've added nearly that level of MA. With that (lower) TA target in mind I will try to stay on top of that over the next few weeks and see where things go. So do you lower to 7.0 each time and then aerate back or simply try to lower to 7.6?

Spa doesn't spill over, its a separate entity from the pool. It doesn't have aeration for the most part (but we can turn on the aerator to add bubbles to the jet and then it does considerably).
 
DougS78 said:
Ahh, Ok, that make sense. I do not think I've added nearly that level of MA. With that (lower) TA target in mind I will try to stay on top of that over the next few weeks and see where things go. So do you lower to 7.0 each time and then aerate back or simply try to lower to 7.6?
Click to expand...

Lowering pH from 8 to 7.6 is for normal pH adjustment.

TA will drop much more when you lower pH to 7.0 - 7.2. You only lower pH that much when you want to deliberately lower TA.

You can do normal pH adjustments to 7.6 and TA will drop slowly or you can work on lowering your TA in a day or two by frequently checking pH and lowering it as soon as you see it is over 7.6.

From Lower Total Alkalinity

The acid/aeration process to lower TA:​

  1. Add acid to lower your PH to between 7.0 and 7.2 (this also lowers TA)
  2. Aerate until PH rises to around 7.6 (the only way to raise PH without also raising TA)
  3. Repeat steps 1 and 2 until you reach the desired TA.
 
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mknauss said:
You do realize the FC should never go below minimum for the CYA, right?
Click to expand...
I try to keep FC up by adding about every other day, but on the occasion I'm off by a day or 2 (vacation, etc) it does get lower.

But no, I didn't realize there was a minimum for the CYA, though. How does one find that value?
 

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