Saturation Index

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George Whitzel

Well-known member
Jul 23, 2017
247
San jose, california
Pool Size
17000
Surface
Plaster
Chlorine
Salt Water Generator
My pool measurements today were as follows:
FC 6
CC 0
PH 7.5
TA 90
CH 100
CYA 60

After testing I read for the first time a card in my Taylor test kit. I used the card to calculate a Saturation Index 0.5.which the card says will cause cloudy water or deposit scale. My pool looks clear. What is this Index for and do I need to worry about the reading I got?
 
Have you discovered the web version of TFP's PoolMath yet?? Enter your numbers in there and play around, at the bottom you'll see your CSI. Ideally you want it -0.3 to +0.3.

www.troublefreepool.com

Calcium Saturation Index (CSI)

How is CSI calculated? Very simple – use our PoolMath tool. To ensure long plaster life and save money, click here to learn more.
www.troublefreepool.com www.troublefreepool.com

Make sure to enter your pool size at the top of page, and your source for chlorine, TFP and vinyl down at the bottom so that the suggested levels are appropriate.

PoolMath

Discover the calculator behind the perfect pool, PoolMath. Dealing with pools has allowed TFP to become the original authors of the best calculator on the net.
www.troublefreepool.com

Maddie
 
You want to pay attention to CSI. Taylor's Saturation Index is kinda old school, if it's what I remember. I don't use that calculator. CSI is the better index for keeping your pool's plaster/pebble surface healthy and happy. I'm kind'a obsessed with CSI and believe it is the key to stretching the lifespan of my pebble. So yes, you need to worry about CSI. I had to replace my 4-year-old plaster because the pool guy I used to use had no clue and destroyed my pool, partly with bad water chemistry (out of range CSI) and finally with a very bad acid wash while attempting to correct the affects of his CSI ignorance. I'm convinced that the years of bad CSI weakened the plaster, and the acid wash finished it off. Since I got my new surface, I'm taking care of it myself (with TFP) and am hoping that this pebble will outlast me, so I don't have to pay for another round. Proper CSI will ensure (or at least help) keep calcium from building up on your surface and minimize undo wear from aggressive water (low pH). Since properly controlling my CSI, I don't see any calcium build up on my pebble. Before, my plaster was virtually covered with it.

Maddie has steered you to an online tool that can help you track your CSI. But TFP's Pool Math app also does a great job of calculating CSI, if having something on your phone works better for you. I use the app and check/correct my CSI every time I test my water (which is at least once a week). I maintain a very stable CSI of about -0.15, give or take. I keep it negative to help keep scale from forming on the plates inside my SWG. If you don't run a SWG, then -0.3 to +0.3 is the general recommendation.

PS. Don't be intimidated by CSI. There are several factors that affect/control CSI, but the primary ones are water temperature and pH. As long as all my other levels are in range (TA, CH, CYA, salt, etc), I only need to play with pH to keep my CSI in range. It's pretty simple once you get the hang of it. When it's hot and the water is warm, my pH is around 7.4 to 7.5. Winter time, when the water is cold, I run my pH up around 8.0. That's all there is to it to keep my CSI where it should be (your numbers might be different for your pool, but that's what the CSI calculator will help you figure out).
 
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I plugged in your numbers and got a CSI of -0.73. That's too low. What did you get? It looks like your CH is pretty low for a pebble pool. I keep mine around 350. There are others here that are better with the chemistry stuff than me, but at first glance I'd say your CH and CSI are out of range. Don't panic, it takes months of whacky CSI to affect your pool, but you should get it straightened out sooner than later... I'm not for certain it works this way, but what I have in my head: if your CH is too high, the calcium will come out of solution and deposit onto your pebble (that's what happened to me). But if CH is low, the water will draw calcium out of the plaster that is holding your pebbles together, and that'a no good. @JoyfulNoise can maybe correct me if I have that wrong.
 
Fill water measurements are as follows:
PH 7.4
CH 300

So I remeasured pool water and CH read 315 (probably did test wrong first time). Using the Taylor test kit card with this CH reading yields a SCI calculation of 0.05 (between 0.0 and 0.1) .
 
Using Pool Math I now get a CSI of -0.24 for your pool, which is in range. Good. Some here will be able to make sense of the numbers you're getting from the Taylor kit, but most all of us use the CSI calculator from Pool Math. Which means you'll get more advice if you switch over from the Taylor calculator to the Pool Math CSI calculator, because we'll all be "speaking the same language."

The following is a bit advanced, but you'll need to come to terms with it eventually. The CH in your fill water is about like mine. And like salt, CH collects in your water and does not evaporate. So every time you add water to your pool you're going to be adding calcium, which is going to continue to elevate your CH (which is why you're now at 315). Rain and splash-out will counteract that rise to some degree, and you can maintain a proper CSI as your CH rises by tweaking some of the other levels that affect CSI. But eventually your CH will get too high and you'll be forced to replace some of the water. But with a CH of 300 in your fill water, you can see that you'll need to replace a lot of water to bring down your pool's CH significantly. My fill water CH is also high, about 350, so I was facing this same dilemma. My solution was to replumb my auto-filler to my water softener. Now I top off my pool only with soft water (CH=0) or rain water (also CH=0). So for the last several years since I did the replumb, my CH has remained stable at about 350, which keeps my pebble happy and my CSI easy to maintain.

If for some reason I didn't like using soft water inside the house (to save my plumbing fixtures), I'd still go out and install a softener just for the pool! My CH doesn't build up, my salt doesn't build up (I think because of the rain in the winter) and so I don't expect to have to ever exchange water in my pool (at least not for those reasons).
 
George Whitzel said:
So with a SWG pool with no heater do i need to be concerned about this CSI calculation or not?
Click to expand...
If you're asking if you can ignore CSI for now based on your current levels, then yes, you're in range. But as I explain in a couple posts above, if you want to take good care of your finish moving forward, you're going to have to monitor CSI regularly, and keep it in range. I believe the more you do so, the longer your pebble will last. SWG or no, heater or no, doesn't matter. CSI is something everybody with a plaster-based finish needs to control.
 
CSI is something everybody with a plaster-based finish needs to control.
Click to expand...
I strongly disagree. CSI is ONLY important if your fill water or other circumstances somehow prevent you from managing your water within TFP parameters..

If you live in the majority of the USA, you can manage these parameters and pay no attention to CSI whatsoever. This subject has been hashed over wa-a-ay more than once but I will just say my fill and refill water in NC was pH 7.4, TA 80, CH 80......CSI is totally irrelevant in that scenario.

The entire East Coast and most of the upper half of the United States has similar water parameters.

In the case of OP with fill of 7.4 pH and CH of 300 he can easily manage that pool and never do ONE csi calculation.......ever. He will likely need to replace some water every couple of years or so as his CH climbs but his pool is manageable without ever giving a thought to csi.
 

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I appreciate everyone responses. My pool is 14 years old and the pebble sheen still looks good and the water is crystal clear. Because of evaporation in the hot California sun I do have to add about 3 to 4 inches of water every week to keep it above my skimmer level. So with my fill water having a CH of 300 I think I will always be in that range for C during the summer months. During the past few winters I had to actually pump water out pool during heavy rains to keep it from overflowing. I record all of my test readings in a logbook and when I look back at them I see that during the rainy winter months my CH is lower than 300. So i think this keeps my overall year round CH from climbing to high. Local Leslies shows a CH range of 200- 400 being in the acceptable range.

As for CSI calculations I am still not sure what an acceptable range is for my pool.

Ps: i will download Pool Math and use it in the future for my CSI calculations.
 
I used pool math to calculate a CSI reading of - 0.23. Pool math model says reading needs to be in range of -0.3 to +0.3. Someone earlier in the replies said they calculated it to be - 0.24 and that was in the OK range?
 
@Dirk, or anyone else - why the Taylor SI index is so different? Why should we so much trust the TFP CSI? was it created by someone special who does that kind of stuff?
It is a bit crazy to see that both are giving me such a different results and... above I can read that actually I could completely ignore it :p

To be honest when I do some simulation on the perfect settings for SWG: FC 5, pH 7.8, TA 80, CA 375, CYA 75, Temp 83 the calculated CSI is perfectly on 0.010
however a tiny change in pH to 7.6 makes a huge change to -0.18, and ph 7.5 moves it to -0.27 It doesn't look to me very maintenance free.
 
We teach you how to get your pool to be TROUBLE free, NOT maintenance free. All pools need maintenance. I do a little every day, and a larger chunk once a week. Other things once a month or once a year. Even with all my automation! My goal was not to eliminate maintenance, but to minimize the time it takes. And to maximize my pool's longevity. For me, where I live, CSI will be playing a large part of both. Keeping my scaling in check, and maximizing the life of my pebble surface. You can ignore CSI depending on where you live and the composition of your fill water (I'm learning that now myself.) and on what type of pool you have. But if your fill water is hard (high CH) and you have a plaster pool that is prone to CH buildup (as mine is), then we need to monitor CSI.

Would it be great if we didn't have to figure this out? Of course! But from my own experience, I know it needs to be done and so someone's got to do it. But I didn't have the choice, because my pool guy didn't have a clue about CSI and destroyed my plaster because of it. $9000 worth! The next guy I hired didn't know this stuff either. So the only way I could be assured of good health for the new pebble was to suck it up, learn this stuff, and make sure it gets done right.

It's not very hard to do. Pool Math does the calculation for you, based on the tests you need to do for your pool anyway. So there are no additional tests or effort to obtain your CSI. All you have to do is just have a look at it and make sure it's in range. If it isn't then you need to make some simple adjustments using household chemicals (most of which you're already likely using). And from the sound of it, you already know how to use Pool Math to figure out what to do. EZPZ.

If it helps, I muscled through the same learning curve. But now, it's nothing. I test, I check the CSI, and then adjust this week's acid dose accordingly. It takes about a minute. If that minute gets me another 5 or 10 years out of my pebble, then that'll be a fair trade!

Regarding your first question, I have read about it, and then promptly forgot the whys of it. My take away was that CSI is the better of the two for monitoring your pool's health, so that's where I landed. Marty has pointed you to an article about it.
 
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Thanks Marty and Dirk. Looks like I'm going to to stay late again reading TFP :p My wife woke up a few nights ago around 2am, saw me reading the TFP page on my phone in the bed and... "it can't be so interesting!" haha. OK, so I will know more tomorrow, at this point I will trust you.

Well, I already decided to trust you and I'm almost there since I started all changes a few days ago. I hope I will not have any issues by following the "Taylor" Langelier index for last two months. It does a bit different math. It was obvious to me it is important and nothing changed except now I'm changing the whole chemistry to the TFP recommendations. I think I was slightly smarted than you, or lucky. I had my pebble installed middle of June so it is about 2 months now. Not having the best opinion about pool service companies I decided to take care of the start up myself from the beginning because I love my new pool :) Ordered the test kit and started monitoring and maintaining everything everyday, researching subject in the meantime. I do not believe any guy for $100-$500 would provide me that level of service. I saved money, learned a lot and I think I'm on the good path to have a trouble free pool. Right, it is not going to be maintenance free :cool:

As you know from another thread I decided to buy and use acid dispenser (set to 100%) because I had to dump so much acid regularly and... in last two days when I started raising my CYA I ended up with turning it off and changing SWG from 85% to 15%. Right now I'm in a bit strange situation (2 days so far).
FC 5.6
pH 7.4
TA 80
CA 375
CYA 60
Temp 83
That results with CSI = -0.33. If I raise pH to 7.8 I will be set on 0.05, however my pH is so crazy stable now that it doesn't want to go up haha. Anyway, I still have my socks with CYA in the skimmer running for another 24hrs so tomorrow my CYA will be around 75 and... this is what worries me. My CSI will be even more acidic ~0.37, if I can call it that way. I think I need to figure out how to bump up the pH. I directed returns toward the surface (I installed Venturi returns) to create a bit of bubbling, turned the waterfall on, and the spa spillover. I read that aeration can help me to achieve it without any additional chemicals. It is not really changing so far.
 
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Uh, dude, not sure why Marty and I are even here. YOU HAVE GOT THIS DOWN!! Pretty much everything you need to know. Even how to correctly use smilies in your posts! ;) Your numbers look good. Your logic sounds good. All good! The only thing I can think to add, and I had to scrape this up, is be careful how you add and test CYA. It can take a while between dosing and testing to get the full result. You want to kinda sneak up on your target amount. So add a little less than you think you should, wait several days, then test. Repeat until you get to your target. It's easy to overshoot if you're not patient, then you have to either wait until it degrades out of your water, or exchange water, to get back down to your target.
 
Also, do not chemically raise pH. Aeration and your curing plaster will do that. The only time you chemically raise pH is if you crash the TA and pH by adding too much acid. Way too much.
 
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