Help: Pool pH 8.0 equilibrium

[HobbitPool]

Hey TFP forum, this is my first post. Just finishing up my first full season of owning a pool. I'm very grateful for TFP Pool School, and all the great resources. Outside some hiccups opening the pool before I knew about TFP, I've had a fantastic season with completely clear water. I test daily for pH, FC, and the others periodically. My pH level seems to find equilibrium at 7.9-8.0, no matter what I do. During the 24hrs around chlorination, it will spike up to 8.1-8.2, but heads back down after that. Even when I use pH reducers (i.e. dry acid/sodium bisulfate) to try to lower it, it generally spikes back up slowly over 36 hours from dry acid addition. I was puzzled by this, so started testing borate levels. The prior pool owner used a pool combo product weekly, "Shimmer" (47.6% Cal Hypo, 20% Sodium tetraborate pentahydrate, 32.4% other, see: Simple Salt Shimmer), and tested at pool stores. I suspect I might have higher borate levels, ~ 100pm, given Taylor test strips. The same test strips tested my non-pool tap water at 15pm, which should basically be 0ppm.

Questions:
1) Should I be concerned about my pH stability around 8.0?
2) Is my borate level of any concern?
3) Is it important to find a more accurate borate test?
* Per TFP articles...
a) "mannitol test for borates has been developed by some creative members. It is a bit complex and you can read about it here."
b) "commercial Borate Alkalinity Test Kit is available...."
4) I will drain about 25% of the pool water (i.e. 1 ft) when closing the pool at end of season. This should reduce borates by about 25%. Any reason to drain more than this?

Today's Tests:
FC: 4, pH: 7.9, TA: 90, CH: 265, CYA: 40, TEMP: 81F, Borates: 100ppm (rough approximate, as at end of Taylor test strip spectrum). Water description: Clear

Sources/What I've Read:
PH - Further Reading
Borates in pool - Further Reading

 

[ajw22]

Welcome to TFP.

No, No, No & No.

 

[reggiehammond]

Your pH is rising because your TA is high. TA can be raised by chemical addition, or from fill water (my well water is ~250 TA)

Use muriatic acid to lower (no dry acid recommended), using effects of adding in Pool Math. When pH gets to 8.0, target 7.2 and dose for that. Once you knock down to 50-60 TA, your pH will stabilize.

Your FC is pretty low - your min is 3 and 4 is below recommended range. Flirting with an algae bloom.

 

[HobbitPool]

@ajw22 Thanks, appreciate your reply.

@reggiehammond Thanks for your detailed message. I'll test my TA in my fill water (public municipal tap), good point for me to know my fill water TA. I prefer not to use muriatic acid, given additional safety factors involved around usage and storage, though I know its preferable from TFP PoV. I don't see any reason why dry acid would be less effective, if one follows PoolMath. Even after three attempts at using dry acid (without accounting for borate levels in Pool Math), I've had no permanent change in TA levels. Why might this be? From a high-level, my understanding is that TA acts as a buffer against pH reduction primarily, and borates primarily act as a buffer against pH rise . I've read the TFP articles indicating that keeping TA lower is more a matter of historical data points/experience in keeping pH stable, as opposed to a detailed chemistry reason. My hypothesis is that my current borate level, requires a lot more acid reducer amounts (i.e. whether dry acid or muriatic acid). PoolMath seems to greatly increase the acid reducer quantity if borate levels are higher. Hence, why I posted earlier about having higher than average borate levels, etc. Does any of this additional context change your answer? Thanks kindly for your consideration.

 

[Bperry]

Hey TFP forum, this is my first post. Just finishing up my first full season of owning a pool. I'm very grateful for TFP Pool School, and all the great resources. Outside some hiccups opening the pool before I knew about TFP, I've had a fantastic season with completely clear water. I test daily for pH, FC, and the others periodically. My pH level seems to find equilibrium at 7.9-8.0, no matter what I do. During the 24hrs around chlorination, it will spike up to 8.1-8.2, but heads back down after that. Even when I use pH reducers (i.e. dry acid/sodium bisulfate) to try to lower it, it generally spikes back up slowly over 36 hours from dry acid addition. I was puzzled by this, so started testing borate levels. The prior pool owner used a pool combo product weekly, "Shimmer" (47.6% Cal Hypo, 20% Sodium tetraborate pentahydrate, 32.4% other, see: Simple Salt Shimmer), and tested at pool stores. I suspect I might have higher borate levels, ~ 100pm, given Taylor test strips. The same test strips tested my non-pool tap water at 15pm, which should basically be 0ppm.

Questions:
1) Should I be concerned about my pH stability around 8.0?
2) Is my borate level of any concern?
3) Is it important to find a more accurate borate test?
* Per TFP articles...
a) "mannitol test for borates has been developed by some creative members. It is a bit complex and you can read about it here."
b) "commercial Borate Alkalinity Test Kit is available...."
4) I will drain about 25% of the pool water (i.e. 1 ft) when closing the pool at end of season. This should reduce borates by about 25%. Any reason to drain more than this?

Today's Tests:
FC: 4, pH: 7.9, TA: 90, CH: 265, CYA: 40, TEMP: 81F, Borates: 100ppm (rough approximate, as at end of Taylor test strip spectrum). Water description: Clear

Sources/What I've Read:
PH - Further Reading
Borates in pool - Further Reading

The borate test strips go bad fairly fast once the bottle is opened. I wouldn’t trust them.

pH will always rise, the only thing you can do is slow it down. pH of 7.8 to 7.9 is fine as long as you can measure it reliably.

Note that dry acids add sulphates to the water which can damage pool surfaces and concrete. Don’t use those. Use muriatic acid instead.

 

[reggiehammond]

@reggiehammondWhy might this be? From a high-level, my understanding is that TA acts as a buffer against pH reduction primarily, and borates primarily act as a buffer against pH rise . I've read the TFP articles indicating that keeping TA lower is more a matter of historical data points/experience in keeping pH stable, as opposed to a detailed chemistry reason.

No need for hypothesis, the chemistry is well understood. More reading here:

PH TA Relationship - Further Reading

www.troublefreepool.com

 

[HobbitPool]

No need for hypothesis, the chemistry is well understood. More reading here:

PH TA Relationship - Further Reading

www.troublefreepool.com

Thanks, this is a very helpful article and table.

 

[HobbitPool]

The borate test strips go bad fairly fast once the bottle is opened. I wouldn’t trust them.

pH will always rise, the only thing you can do is slow it down. pH of 7.8 to 7.9 is fine as long as you can measure it reliably.

Note that dry acids add sulphates to the water which can damage pool surfaces and concrete. Don’t use those. Use muriatic acid instead.

Thanks for your response. Good to know that borate test strips don't last long after opening.

 

[Mdragger88]

During the 24hrs around chlorination,

What does this mean? Are you not chlorinating daily?
If you’re using liquid chlorine for chlorination I think you’re correlating two different things that are unrelated unless you’re raising fc higher than 10ppm which invalidates the ph test. It can make it read falsely high.

 

[HobbitPool]

What does this mean? Are you not chlorinating daily?
If you’re using liquid chlorine for chlorination I think you’re correlating two different things that are unrelated unless you’re raising fc higher than 10ppm which invalidates the ph test. It can make it read falsely high.

Thanks for your message, I could have wrote that phrase a bit clearer. What I meant by "24hrs around chlorination" was that if I measured the pH within the first 24 hrs of adding chlorine to the pool, I typically get a temporary increase in the pH. I don't measure the pH immediately upon adding chlorine, but typically about 12 hours later (i.e. the morning after adding chlorine post-sunset the prior evening) and then the next evening (i.e. 24hrs later). In almost all cases, the FC level <= 10 during those measurement periods, so pH readings should be relatively good. While I use the TFP-Pro pH test often, I also use the TFtestkits pH meter add-on (i.e. p95 pH meter), regularly calibrated. For what's it's worth, I don't know what the p95 meter accuracy is like above FC=10, couldn't find a spec sheet on the website. For chlorine source, I use cal hypo, 68%, easier to store and keep safe from small kids in the limited storage space.

 

[Mdragger88]

The meter should be unaffected by higher fc levels.
Be careful with the cal hypo- it is one of the most dangerous forms of chlorine to store.
Be certain it is stored separately from all other chemicals as it can cause an explosion if it is allowed to mix with other chemicals in its dry state.
It also raises your ch with each dose-which can only be lowered through water replacement.
Having low ch is not a problem in vinyl pools but high ch can cause scaling problems in all pools. Your pool falls into the “do not add” category.

 

[reggiehammond]

For chlorine source, I use cal hypo, 68%, easier to store and keep safe from small kids in the limited storage space.

There's definitely an argument to be made that CalHypo is actually one of the more dangerous things around kids/animals.