Intentionally raising CYA to lower ph ceiling

[Nfrisa]

I have to add about a gallon of Muriatic acid a week to keep my ph in check. It will go up above 8.0 and I add half a gallon. Within 2-3 days it’s back above 8.0. I’ve been looking for ways to mitigate this fast ph rise.

I was messing around with the Orenda app because it shows you the theoretical ph ceiling. One thing I noticed is as I raise CYA the ph ceiling comes down. If I raise CYA to approximately 140 the ph ceiling comes down to 7.9 and I could let it ride there. My question is would this be an acceptable way to manage the ph rise? Are there any downsides to keeping CYA that high?

My current numbers with Taylor drop test are:
Ph above 8.0
Alkalinity 80
Calcium 400
CYA 80
Chlorine 6.5
Salt 3,200
18 month old plaster pool 13,000 gallons

 

[Bperry]

I have to add about a gallon of Muriatic acid a week to keep my ph in check. It will go up above 8.0 and I add half a gallon. Within 2-3 days it’s back above 8.0. I’ve been looking for ways to mitigate this fast ph rise.

I was messing around with the Orenda app because it shows you the theoretical ph ceiling. One thing I noticed is as I raise CYA the ph ceiling comes down. If I raise CYA to approximately 140 the ph ceiling comes down to 7.9 and I could let it ride there. My question is would this be an acceptable way to manage the ph rise? Are there any downsides to keeping CYA that high?

My current numbers with Taylor drop test are:
Ph above 8.0
Alkalinity 80
Calcium 400
CYA 80
Chlorine 6.5
Salt 3,200
18 month old plaster pool 13,000 gallons

The higher the CYA, the higher the chlorine “floor” becomes. Your 6.5 above would be the bare minimum never allowed to go below that. You should simply lower your TA to 50/60 and the pH rise will slow down a lot. I haven’t had to add any acid at all this season yet.

 

[Nfrisa]

The higher the CYA, the higher the chlorine “floor” becomes. Your 6.5 above would be the bare minimum never allowed to go below that. You should simply lower your TA to 50/60 and the pH rise will slow down a lot. I haven’t had to add any acid at all this season yet.

I know I would have to keep my chlorine level higher but I have a salt water generator so once I get the chlorine up to 8-9 it doesn’t cost me anything to keep it there.

I would love to lower my TA and I’ve tried but my fill water has a TA of 80-90. The pool is in the sun all day with a high evaporation rate and autofiller. so I can’t get TA any lower.

 

[Nfrisa]

The higher the CYA, the higher the chlorine “floor” becomes. Your 6.5 above would be the bare minimum never allowed to go below that. You should simply lower your TA to 50/60 and the pH rise will slow down a lot. I haven’t had to add any acid at all this season yet.

The other option would be to just let my pH ride at 8.1-8.2. The CSI is close to zero so it doesn’t seem like it would be a problem. But I know people have mixed feelings on that.

 

[Bperry]

The other option would be to just let my pH ride at 8.1-8.2. The CSI is close to zero so it doesn’t seem like it would be a problem. But I know people have mixed feelings on that.

No one here has mixed feelings about that. But it’s hard to measure pH above 8 with the Taylor kits since they max out at 8.2. I’d also ditch the orenda app and just use poolmath.

If you lower your pH to 7.2 each time it gets to 8.0, the TA will drop a little. Do it enough times and the TA will come down. You can speed up the process by aerating the water to raise the pH (but not the TA). That’s how we advise people to lose their TA when they have aggressive TA fill water. (Hint: you don’t have aggressive TA fill water. Some folks have 200ppm TA fill water).

 

[ajw22]

The other option would be to just let my pH ride at 8.1-8.2. The CSI is close to zero so it doesn’t seem like it would be a problem. But I know people have mixed feelings on that.

Pool chemistry is about science, not feelings.

Aim for a pH of 7.8 and lower it when it gets to 8.2.

Watch out for scaling as your CH accumulates.

You would rather be adding acid then dealing with scale.

 

[Newdude]

I would love to lower my TA and I’ve tried but my fill water has a TA of 80-90. The pool is in the sun all day with a high evaporation rate and autofiller. so I can’t get TA any lower.

Let's revisit this with the suggestions above.

Evaporation is one thing but you average 5 ft of rain a year and it was 79 inches in 2021. You dont evaporate substantially more than 1 to 1.5 pool volumes.

When you do add fill, it will raise the TA a little and you will quickly knock it back down when done properly.

 

[duraleigh]

Do NOT manage your pH using CYA........Bad practice.

As others have said, lower your TA down to 50-60 and your acid use will slow down

 

[duraleigh]

what is the pH and TA from your source water? (autofill)

 

[Nfrisa]

what is the pH and TA from your source water? (autofill)

Fill water just tested with Taylor drop kit:
TA 150 (knew it was high but forgot how high)
Ph above 8.0. Looks like 8.1-8.2

I’ve tried to drop ph to 7.2 and aerate repeatedly but it has little effect. heck twice a week I add 2 quarts of acid which should bring it down To 7.2 every time but TA stays around 80.

 

[Newdude]

What is your run schedule for your water features/ spa ? (How much are you aerating?)


A leak needing constant refilling is more likely than evaporating as much as you think over the rainfall totals. Or your overflow line is wasting all the rain, so any evaporation needs refilling.

 

[Nfrisa]

What is your run schedule for your water features/ spa ? (How much are you aerating?)


A leak needing constant refilling is more likely than evaporating as much as you think over the rainfall totals. Or your overflow line is wasting all the rain, so any evaporation needs refilling.

My pool pump runs 60% for 10 hours during the day and 90% for 6 hours in the afternoon/evening

There are no water features running but I do have the main pump linked to 3 bubblers in the pool deck. When running at 60-90% this makes the bubblers barely break the surface. Not really sure if you consider that a water feature.

 

[Newdude]

water feature.

Water features is anything that breaks the surface tension causing Ph rise. It sounds like youre running way more than you need to and spiking the Ph. Features need purging once a day for a couple minutes when not in use. Twice a day for 10 mins is even better.

Then run the pump only for a reason, and as low as possible when doing so. You probably skim well at 1/3 of the speeds youre running. The heater may need a little more but still below what youre running.

 

[pjt]

The pool is in the sun all day with a high evaporation rate and autofiller. so I can’t get TA any lower.

Harvest as much rain water as possible. Minimizing use of the autofill will help.

Some folks have 200ppm TA fill water

330 here.

 

[Nfrisa]

Water features is anything that breaks the surface tension causing Ph rise. It sounds like youre running way more than you need to and spiking the Ph. Features need purging once a day for a couple minutes when not in use. Twice a day for 10 mins is even better.

Then run the pump only for a reason, and as low as possible when doing so. You probably skim well at 1/3 of the speeds youre running. The heater may need a little more but still below what youre running.

Good to know, I’ll adjust my schedule.

Is there a better way to lower my TA or is it just difficult due to my fill water?

 

[JamesW]

If I raise CYA to approximately 140 the ph ceiling comes down to 7.9 and I could let it ride there.

The reason is because the carbonate alkalinity drops with higher CYA.

Don't go to 140 on CYA.

You can lower the TA; it is really not that hard.

Test the pH daily and keep the pH at 7.2 for a week by adding acid and see what the TA does.

 

[PoolStored]

You would rather be adding acid then dealing with scale.

^^^This. For advanced TFPers, If you have TA in the 80-90 range

Is there a better way to lower my TA or is it just difficult due to my fill water?

You can use your water features to your advantage...

Lowering Total Alkalinity (TA) Quickly with the Acid Aeration Method

Thought I'd make a post that might help others. We've had quite a few members this year with high TA, and I've been typing the same information over and over. I'm going to post this so I can link it to help others. High TA can cause rapid pH rise. High TA is typically caused by high TA fill...

www.troublefreepool.com

 

[JamesW]

I am not a big believer in Borates, but you might want to consider them.

They also help lower the Carbonate alkalinity.

Borates and Adjusted Alkalinity.​

Adjusted TA = TA – (CYA X CYA C.F) – (Borate x Borate CF)

Borate C.F (correction factor) based on pH.

pH.......CF

7.2.....0.051

7.4.......0.0786

7.6......0.1248

7.8......0.1989

Cyanuric Acid correction factor based on pH.

pH........CF

7.0.......0.22

7.1.......0.24

7.2.......0.26

7.3.......0.28

7.4.......0.30

7.5.......0.32

7.6.......0.33

7.7.......0.34

7.8.......0.35

7.9.......0.36

For example, if the pH = 7.6, TA = 90, Borate = 50 and CYA = 70, the adjusted alkalinity is 90 - (70 x 0.33) – (50 x 0.1248) = 60.66.

Borates in pool - Further Reading

www.troublefreepool.com

 

[Nfrisa]

The reason is because the carbonate alkalinity drops with higher CYA.

Don't go to 140 on CYA.

You can lower the TA; it is really not that hard.

Test the pH daily and keep the pH at 7.2 for a week by adding acid and see what the TA does.

So maybe I was only being the ph down to 7.2 once or twice a week and that wasn’t enough?

Should I be checking it every day and adding acid every day for a week to try to keep it that low?

 

[Nfrisa]

^^^This. For advanced TFPers, If you have TA in the 80-90 range


You can use your water features to your advantage...

Lowering Total Alkalinity (TA) Quickly with the Acid Aeration Method

Thought I'd make a post that might help others. We've had quite a few members this year with high TA, and I've been typing the same information over and over. I'm going to post this so I can link it to help others. High TA can cause rapid pH rise. High TA is typically caused by high TA fill...

www.troublefreepool.com

Are you saying TA 80-90 is a problem? Not sure I understand your response.