Extreme Climate Las Vegas Pool


Oct 7, 2019
Las Vegas
Hi everyone!

I was reading now since several weeks, and decided to join the form. What a wealth of amazing information!
I do have a couple of questions to the experts in this forum and would like to thank in advance for any comment!

1. I am in Las Vegas, extreme heat in summer, extreme dry (humidity under 10% normally) during the year.
Plaster pool, 5 years old, Pentair SWG, Pentair Cartridge Filter, Pentair Pool Pump, 25k gallon.

2. I have pool services coming and going for the past 2 years since I bought the house and after reading on this website,
I decided to get rid of the pool guy and do it myself, as it seemed that he did not keep any parameters in line with recommended

Currently my pool as following parameters:
TA 70
FC 7
CYA 20
PH 7.5
Calcium Hardness 800
Salt: 3600
CSI from 7.2-7.8 PH around -0.3 to + 0.3 with those paramenters and currently around 75F.

3. I am facing following problems:

a) Very high evaporation level. Put total new tab water 2 years ago, which is TH of around 260. Now my pool water has calcium hardness of around 800 (acc. to Taylor test kit).
Tab water has TH of about 260 in Las Vegas. Pretty hard to start with. I did have a massive calcium scaling problem when I had a pool service, now when I balance the water myself I do not have it. My question is, if I need to drain the water or keep on going with such high CH? Will this irritate skin at one point and make the water unpleasant? Should I add borates if my water is already so saturated wit calcium? Would a liquid pool cover (polymer) help to reduce evaporation and thus keep calcium levels rising slower?

b) My pool includes designs (spa overlow into the pool and a platform) that are made of stones including lots of iron naturally. I had my stairs under the platform getting brown every couple of months. I now treated the stairs with abscorbic acid and I add bi-weekly Jack`s Magic Sapphire Stuff to bind metals in water. I was thinking if sealing the stones would bring any improvement, or, if I need to take any further action that the Sapphire Stuff to keep my pool from staining in future again. I assume previous pool services had also a higher PH than 7.8 which maybe caused part of the problem. Any recommendation on how to keep the pool stain free even having natural iron rich stone in it?

c) The is one spot in the pool where it seems that reinforcement steal or a metal is rusting out of the plaster. It is dia 1 inch brown spot. What would be the best solution about this problem? Just sealing it e.g. with sealing silicon glue the next time I drain it so the steel has no contact with the water?

d) My pool requires about 1 gallon of 14.5 muriatic acid at TA 70 to go from 7.7 back to 7.2. With the pool math calculator, adding my details, I would just need a 3/4 gallon.
Not sure if there is an error with my data or if there is something else off with my pool or if this sounds about right?

e) I do not understand why with a SWG pool, CYA is recommended so high? Is there any issue with keeping it at 10-20? As the pool pump is 8-10 hours in operation it seems that even at 70-80% capacity there is never a problem with FC levels even with a strong Las Vegas sun. Never had an algae issue.

f) Pentair SWG offers the option of "Superchlorination". Can this be considered a shock treatment especially with low CYA?

I know these are many questions at once, but any comment will be much appreciated.


Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Welcome! :wave: While I live in S.A. now, I grew up there and just returned from a short visit, so I know the area quite well. Some things to keep in mind ....
- Good job taking ownership of your chemistry. You're much better off that way. :goodjob:
- A CH of 800 is approaching the point of water exchange. Some will do their best to compensate by lowering the TA and pH as much as they can, but soon a healthy water exchange will be needed. When you do, it's best to do that in the colder months (Dec - Feb) which is best for plaster while it's exposed. With high CH fill water, it's never low, but it should be better. Things to keep in mind to help are (yes) a cover to slow evaporation (dry air and windy days), rain water collection (monsoon season best), and suppliment by adding softened water.
- The elevated CYA is to help presevre your SWG-produced FC and help maintain a longer cell life. In the 2-4 cold months when water temps drop, you might get-by with a lower CYA, but in the high-heat seasons it's best to have it higher (70).
- The superchlorination feature may be helpfull in a pinch, but not if you ever get algae and have to perfomr a SLAM Process.
- The metal rust spot sounds like rebar trying to come through and bleed through the plaster. I don't think there's much you can do with that unless you get into it (physically) at a future re-plaster date.
- The suspected staining from the stones used in your pool is interesting. I'll ask someone like @JoyfulNoise to see if he has an opinion.
- Stick close to the PoolMath tool or APP. As long as your pool parameters are loaded correctly, it will help tremendously with your dosage amounts. Also keep an eye on your "CSI" level to keep it slightly negative if possible. I know it's a challenge when the CH is so high, but at least you know.

Hope that helps. Welcome to TFP! :swim:
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Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Welcome to the forum.
I am in more extreme climate Laughlin!

As Pat described, your CH is getting close to where it is hard to keep from scaling. I get about 16 months and then do a full water exchange.

I would recommend following our CYA levels. If mine goes below 70 ppm I see a dramatic rise in FC loss during the swim season.
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Oct 7, 2019
Las Vegas
Thanks for the great answers! Greetings to the very south of wonderful Nevada! P.S. will the high calcium bring skin discomfort at one point or is it purely a scaling problem?
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