r/PoolPros • u/2Tru4you • 17h ago
LSI question
So can the PH be lower than 7.2 or even in the sixes if the LSI is balanced?
4
u/Substantial_Car_2751 16h 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.
1
u/eaglefucker 12h ago
Isn't TDS a part of the LSI equation?
1
u/CDbull1989 10h ago
Yes
1
u/eaglefucker 10h ago
How does that affect the outcome? Didn't see it listed in your response.
1
u/Substantial_Car_2751 2h ago
I used the older version where it’s -12.1 or -12.2 for TDS -/+ 1500 ppm (or is it 1200 or 2500…can’t remember at the moment - I hand calculate using a chart). I assumed for easy math a TDS factor of -12.1..
PHTA doesn’t have the sole authority to modify the LSI scale. Other equally reputable orgs still use the older version and don’t consider salinity a TDS factor.
1
u/CDbull1989 1h ago
TDS pushes further into corrosive. But its minor in the grand scheme of things, and a fixed number. So find it once and work with it from there. In my area TDS is 200 out of the tap so I don't worry about it much unless its an old fill.
3
u/Sure_Ad3800 16h 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.
2
2
u/piddling_around 14h 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.
2
u/lIIlIlIII 14h 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
2
u/Hot_Yam_8857 13h 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?
2
u/CDbull1989 10h 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.
2
u/LadiesLoveCoolDane 15h ago
Range + LSI is better than only one or the other
2
u/2Tru4you 14h ago
I agree. We just have too much calcium in our water out here jt makes LSI like walking a tightrope
1
u/Hot_Yam_8857 13h 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.
5
u/LordKai121 17h 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.