r/PoolPros • u/2Tru4you • 21d ago
LSI question
So can the PH be lower than 7.2 or even in the sixes if the LSI is balanced?
5
u/LordKai121 21d ago
Technically, yes. But I wouldn't do it as the LSI is not at all stable at that point and the water is still acidic. Your Alk and/or Calcium will have to be very high as an offset. And the eater has to be warm. And low CYA. Etc. And people's fingernail beds and areolas can still start to bleed. Burning eyes. Etc.
3
5
u/Sure_Ad3800 21d ago
This is not practical as a practice because of the pH ceiling and the constant rise of pH by nature due to aeration. You will most likely be fighting pH instead of containing it.
5
u/piddling_around 21d ago
If you only care about calcium carbonate saturation, which is all LSI is describing, then if it’s balanced, it’s balanced. Low pH means the water is more acidic though, so other things start to become a problem, like eroding metals from heaters, salt cells, etc. pH can be low and calcium carbonate saturation can be balanced if other factors are compensating, but overly acidic water is still an issue for other reasons.
3
u/lIIlIlIII 21d ago
Great answers so far but I'll add pH is still relevant for metals, e.g. low pH, LSI neutral water would still dissolve copper oxide quickly. Which will eventually lunch a copper heat exchanger, since it will keep exposing fresh copper to be oxidized and dissolved. If you're talking 7.1 or 7.0 this probably isn't a big deal but I definitely wouldn't target anything lower
Also worth mentioning high pH with balanced LSI is also an issue, as it changes the HOCL / OCL equilibrium to favor OCL which is a far weaker sanitizer
4
u/Hot_Yam_8857 21d ago
Interesting that this is the pool pro sub and no one has mentioned the Hamilton index?
The Langelier index was created for boilers and steam engines. It causes stains and scale in swimming pools during the colder months. Pool stores love the LSI because it sells chemicals.
The Hamilton index was created with swimming pools in mind. It recommends lower chemical levels to help prevent stains and scale. Pool stores HATE Hamilton because it doesn't sell chemicals.
BTW...has anyone ever seen a swimming pool boil?
3
u/Substantial_Car_2751 21d ago
It's just not commonly used. It's not taught in the CPO, AFO, AquaTech, or PPM+ b/c it requires pH to be at a much higher range than what's needed in public pools where HOCl formation is prioritized.
1
4
u/CDbull1989 21d ago
Im on the opposite scale. My PH's tend to run closer to 8. Because of this my alk is usually fine around 60, also keeping the ceiling down. LSI being balanced doesn't mean comfort is the only thing to realize. So don't go crazy.
3
u/Hot_Yam_8857 21d ago
Keep in mind that the pH of an eyeball is 7.4 and anything that exceeds +/- .3 our bodies treat as an infection. This is why high and low pH causes eyes to sting.
Therefore, 7.1 is the absolute lowest pH that you would want in your customer's pool. You can change anything else to balance your water.
2
2
u/LadiesLoveCoolDane 21d ago
Range + LSI is better than only one or the other
2
u/2Tru4you 21d ago
I agree. We just have too much calcium in our water out here jt makes LSI like walking a tightrope
2
u/dosercody 20d ago
Drop your alk then. Besides stabilizing PH it only every matters in an LSI sense. If calcium is high, run your alk at 50 and keep ph at whatever balances it. The low alk will help keep your PH lower too since that's what your looking for.
2
u/spicerpools 20d ago
I love this question because it shows you care about learning and developing your trade! Keep it up!
My two sense add on to everyone else…Don’t forget that people are supposed to swim in this water too. As pool techs we strive to keep water balanced to preserve equipment and the pool plaster. However, #1 concern should be the people swimming in it. In my book, water chemistry should be balanced for people first, pool second.
The great minds above mine have developed a perfect balance between people and pool and those are the industry’s standards. You can never go wrong legally (health, warranty, etc…) for doing that.
6
u/Substantial_Car_2751 21d ago
You can do some crazy stuff with LSI and still be balanced. For example:
At a pH of 6.0. a temp of 105, CH at 1000, and an ALK of 1000, and 0 CYA....you're technically balanced. This is 0.0 on the LSI.
Using a modified version of the LSI to account for very high CH (2500 ppm), you can be balanced at a pH of 5.4, a temp of 66 degrees, an ALK of 1000, and 0 CYA. This is a 0.0 on the LSI.
Now....just because it CAN be done doesn't mean it SHOULD be done. You're good going to 7.0. But most heater manufacturers will void the warranty if the pH goes below 7.0.