Pool Math vs. our Pool Professional

Erin R

Bronze Supporter
Mar 14, 2019
Tallahassee, FL
Thank heavens for this website, which has helped my family manage our pool for the last several years! But we recently had an equipment failure that required professional help, and the professional who helped us strongly disagreed with how we've been managing our SWG and pool chemistry following TFP's Pool Math instructions. I'd be grateful for some guidance on which way to go from here. Three issues came up involving the SWG and balance between FC and CYA; I hope it's okay to post them all in the SWG forum, because I suspect they may be related:

(1) Run Time vs. Efficiency. For several years, we had been following advice we saw here about some studies showing the SWG can do better running at higher percentage efficiency for a shorter run time than lower efficiency for longer run times. We usually set our timer to run the pumps and SWG between 4-5 hours (shorter in colder weather) at 85-90% efficiency. Once we started doing that, our electric bill dropped $100 per month, and the water was usually in great condition. This professional said that such a high percentage would kill the SWG, and he reset it to run for 10 hours a day at 40%. He also said that electricity was cheaper than the chemicals I would otherwise burn through--although that has not been our experience. Is there a right answer to this question? Can it be done either way, or are we really killing the SWG by running it at 85-90%?

(2) TFP Pool Math vs. SWG guidance on FC-CYA levels. The professional was also shocked that I was aiming for a free chlorine level of around 8, with levels occasionally going as high as 10 (during cold months when we're not in the pool). He said that the FC level should be between 2-3, and pointed to instructions on the inside cover of our SWG display, which did suggest levels closer to 2-3. He said that keeping the FC level so high would bleach out our vinyl liner, and would make the water bad for swimmers. My husband, who kept the water clear and pleasant for years, said that we'd have an instant algae bloom at a level of 2-3. I pointed to the Pool Math recommended guidelines showing much higher recommended levels, but the professional he said these numbers couldn't be right, and that commercial pools are legally required to close if the FC level gets to 10. Again, I'd be very grateful for advice about where to aim, and why there seems to be a difference between the guidance on our SWG display and the pool math on TFP.

He was also shocked that I was aiming for CYA levels between 50-60 and said it should be more like 100, which is way higher than TFP recommends, and even higher than our SWG display recommends. He said that the higher the CYA is, the lower percentage of time the SWG can run, and the longer it will last. He also said that every time I add a bag of salt, I should add a pound of stabilizer. I learned about the relationship between FC and CYA on your website, but my husband always took the opposite approach to the balance: keeping FC high and being conservative about adding too much CYA because it's so hard to reduce it if you overcorrect. I'd be grateful for advice about which way to go here.

(3) Cleaning the SWG with a Vinyl Pool. Finally, my husband used to clean the SWG at least once or twice a year, even though we have a vinyl pool. The professional told me that I never need to clean the SWG at all, and that he never does. He said that it was unnecessary with a vinyl pool, but needed with a cement pool. Is he right? I'd love to not have to do that if I don't really have to. Maybe it depends on the percentage efficiency you're running it at?

I'd be very grateful for any and all advice on how to reconcile this man's advice with what had been working for us for the last few years! --Erin
May 3, 2014
Laughlin, NV
I'm sorry, but the 'pool professional' is wrong.

The SWCG could care less whether it is set at 1% or 100%. It has a finite number of generating hours. Run it as you had been. Save $$ on electricity.

This person also does not understand the FC/CYA relationship. Typical. I would strongly suggest following TFP recommended levels.

The SWCG should not need to be cleaned, ever, if you are managing your CSI to between 0 and -0.3. Input your recent test data (I assume you have a proper test kit) into Poolmath and CSI is calculated for you.
As far as what he said - hogwash - if the water chemistry is allowed to go into scaling tendency then the SWCG will get scaled somewhat. It has no idea if it is adding chlorine to a vinyl pool or gunite pool.

I highly recommend not using that person for any pool water chemistry again.


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Trust what your eyes are telling you.

The SWG cell has the same life and CL output if you run it 10% for 10 hours or 100% for 1 hour.

Smile, wish the Pool Professional a nice day, and continue with your pool your way.


TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
NW Ohio
So he points to the suggested numbers on the SWG to back up his opinion that FC can't be high, but then tells you the CYA should be high and when you point to the SWG suggested numbers he tells you they are wrong?

That tells us a lot about his way of thinking...

Gene Clean

In The Industry
Aug 19, 2018
Modesto, CA
That poor pool man. Being taken by the big company standard. Every pool tech is taught it and that's why they think that way. I know because I was one of them. It's hard to accept the TFP method after years and years in the business. It's so different from the standard we've all been taught. Like everyone else here. I tried it and it's now the only method I use. I'm spreading the word to fellow Pool techs so hopefully it catches on sooner than later.
Likes: Leebo


Mod Squad
LifeTime Supporter
Jul 10, 2012
Tallahassee, FL
Erin good for you for checking! Better to be sure but man he has it all wrong but like Gene said he is only saying what he has been taught. It is sad the info is outdated and not backed by science though. TFP has spent many years, hours, bucks, effort, etc to come up with our way of pool care. There are many papers and articles we could point you to BUT since your pool has done so well already I think you already KNOW what is right for your pool.

Now go look at your pretty pool and know you are taking the best care of it out there!! :hug:


Bama Rambler

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
Everyone here has done an excellent job of refuting the "pool professional" but just to lay it out in bullets like you posted it.

1) Run Time vs. Efficiency.
The percentage on SWG's for the most part just set the amount of time the cell is own per a given length of time. So the cell "works" just as hard when it's on at 10% as it does at 100%, it just takes 10 times as long at 10% to produce the same amount of chlorine running it 100% would produce. That amounts to exactly the same amount of cell life to produce 10ppm of chlorine whether at 10% or 100%. The only thing runnig it at a lower percentage does is cause you to have to run your pump longer and increase your power usage, as you've already found out.
Also, thousands of us vinyl pool owners keep our FC on the high end according to the FC/CYA chart and we've never had a problem with fading. He has no idea how high the FC would have to be to even be a factor in fading a pool liner. The sun is a much larger factor in fading than any FC will ever be.

2a) TFP Pool Math vs. SWG guidance on FC-CYA levels.
As said above, he doesn't understand the FC/CYA relationship. He also doesn't understand the buffering effect of CYA. If your pool had zero ppm CYA then you should run it at 2-3ppm FC, but once you add CYA to the mix then you need to raise the FC to match. Also having 10ppm FC in a pool with 50ppm CYA is actually like having less than 2-3ppm FC with zero CYA in the water.

2b) TFP Pool Math vs. SWG guidance on FC-CYA levels.
Donldson hit the nail on the head about this. He argues for one mfg's recommendation and then argues against another. Sorry, but he's wrong on both counts!

3) Cleaning the SWG with a Vinyl Pool.
Again, he's showing his ignorance. He has no idea what causes a SWG cell to scale. It has absolutely nothing to do with the pool surface material. Rest at ease that it has nothing to do with SWG runtime percentage either.

So as others have said, Keep doing what you were doing before the "professional" showed up.


Gold Supporter
TFP Guide
Jun 7, 2017
Damascus, MD
My former pool start-up guy would laugh at me when I mentioned to him what I learned on TFP for pool chemical balance. He asked, "Did you hear that, 'online'". He felt the guess strips were adequate testing and that flinging (literally flinging over the edge) chemicals into the water was the right way to go. He lasted 3 visits and I called his company and told him I did not require their services anymore. You have to look at where these "professional" chemical levels come from. That is, companies that sell you products. They not only sell products that keep your water "balanced", but also products that rid you of algae and other water "repair" calamities. Most of them preach the weekly "shocking" is necessary. I have never once, not even a single time, ever "shocked" my pool. I have never once had a spec of algae. My water is near perfect, all the time, with a minimal amount of chemical additions. With a SWCG there is very little needed to add during the season. I suggest you nod politely at clowns like this, send them on their way, and trust the TFP method. Your results speak for themselves!

Erin R

Bronze Supporter
Mar 14, 2019
Tallahassee, FL
Wow, I can't tell you how grateful I am for all your replies! Today I reset the SWG back to running at the higher percentage for the shorter time, and will continue to follow the Pool Math approach on water chemistry. Thank you all so much for your reassurance--this is a wonderful forum! --Erin
Likes: kimkats