Struggling with newer fiberglass pool

tech135797531

Member
Jun 14, 2019
12
FL
Hello everyone,

I have a 1 year old San Juan 10k fiberglass pool that the installer left with metal stains. I was finally able to get rid of most of them over the last 2 weeks and I'd like to get my water balanced to where it needs to be. As of 3 hours ago, here are my levels:

FC - 1.8 - I got it back up to 2 after adding liquid chlorine a bit at a time for 10 days after using ascorbic acid. And now I've just turned on the SWG to 8% to keep it around 1.5-2.
CC - 0.0
PH - 7.4
TA - 65ish
CH - 190ish
CYA - 35ish (if I squint real hard I can still see the darn dot)
Water temp 55 degrees at the moment. (I'm in NE FL and it's been chilly lately).

I have not tested my tap water but I've only added 2 inches once 6 months ago because of all the rain we get. Instead, I drain 2-3 inches once a month.

Here are my questions:
1. The San Juan book and the their rep says that the TA should be 125-150. But everything I have read online including here mentions to keep fiberglass pools in the 60 to 90 range. Which one is it?
2. The SWG and liquid chlorine raise the PH which I have to reduce with muriatic acid which then lowers the TA which I then have to raise with baking soda which still raises the PH some. But this is a never ending cycle. Is there a magical way to end this cycle?
3. The TFP's Recommended Levels are 350-550 for CH and 70-80 for CYA - but again this goes against what my manufacturer recommends which is 175-225 for CH and 30-40 for CYA which I'm perfectly in the middle of. Where should I be?

Thank you for all your help. My profile lists all my equipment and I am trying my best to learn and do the right thing. Thank you!
 

JJ_Tex

Gold Supporter
Bronze Supporter
Jul 17, 2019
2,298
Prosper, TX (DFW)
Pool Size
13000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I think your #1 priority should be your chlorine. Why are you targeting 1.5-2? If you look at the FC/CYA charts, 2 is below the minimum for anything (salt/non-salt, low CYA, etc.). You are risking getting algae, especially when the water warms back up.

While the salt water chart doesnt go down to a CYA of 35/40, I would at least shoot for a target FC of 4.

Once you get your chlorine in line, I would look at your pH. Your test above is 7.4 which is great. When are you adding acid? Ideally you can let it rise up to 8.0 before knocking it down. That will hopefully let you go longer without adding acid and help keep your TA in line.

I'll let others address your other questions, since I do not have fiberglass. I will say that on my gunite pool, I have always managed to TFP specs and never had any issues.
 

tech135797531

Member
Jun 14, 2019
12
FL
I guess that's another good question. Everything I have read and been told (including San Juan's book) states that the FC should be 1-3 (they actually say 1-2ppm). I have kept it all last summer at a steady 2ppm and I never got algae. So it seems like everything that the manufacturer is recommending in their booklet does not match up with the recommended values here. I also know that high chlorine levels can promote metal staining in fiberglass pools that have been exposed.
 
Last edited:

JJ_Tex

Gold Supporter
Bronze Supporter
Jul 17, 2019
2,298
Prosper, TX (DFW)
Pool Size
13000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Me again... Just wanted to point you to the article below for the ideal levels. I know that TFP differs in what pool manufacturers and chemical companies recommend, generally around the FC levels. It has always been explained to me that most of the pool world is still based on industry science from the 60's and 70's and uses constants for FC, generally FC of 1-3.

TFP recognizes the relationship between FC and CYA, which is newer science and starting to be accepted but the industry is being slow to adopt. The FC/CYA relationship means that your FC should be proportionate to your CYA level, as seen in the chart.


 

tech135797531

Member
Jun 14, 2019
12
FL
@JJ_Tex, I now understand and thank you for the information. I've done further research into this and I get it now. I'll address the FC issues as you suggested.

Can someone help with my questions from the original post?
 

tech135797531

Member
Jun 14, 2019
12
FL
Hey guys, I'm going to make one last plea and see if there's someone who can provide some insight into my question. I've spent an unhealthy amount of time looking for answers online and no two opinions are the same.
 

MiguelACA

Silver Supporter
May 12, 2020
151
Houston
I was in the same boat as you @tech135797531, following the "industry standards" when I first got my pool. The water was clean and clear, or so I thought...never had algae, or so I thought. While I have never had a full blown algae bloom problem, I did notice a yellow/green film showing up by the tanning ledge skimmer and tiles every week. Figured it was normal...nope, not normal. Decided to go the TFP route, now my pool is CLEAR and have yet to see any of the algae come back. I haven't had to shock/slam the pool at all. These guys and gals have been doing this for a long time, they cant all be wrong, right? Go with the methods here, save some money, and enjoy your pool!
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Here are my questions:
1. The San Juan book and the their rep says that the TA should be 125-150. But everything I have read online including here mentions to keep fiberglass pools in the 60 to 90 range. Which one is it?
2. The SWG and liquid chlorine raise the PH which I have to reduce with muriatic acid which then lowers the TA which I then have to raise with baking soda which still raises the PH some. But this is a never ending cycle. Is there a magical way to end this cycle?
3. The TFP's Recommended Levels are 350-550 for CH and 70-80 for CYA - but again this goes against what my manufacturer recommends which is 175-225 for CH and 30-40 for CYA which I'm perfectly in the middle of. Where should I be?
Tech, it looked like you requested some specific replies to your questions, so I wanted to be sure we did that for you as follows:
1. The TA can vary and we have a lot of leeway. Finding the right TA is often times based on your equipment (i.e. SWG) and how quickly the pH rises in your pool. The higher industry range often is needed to compensate for owners who use acidic pucks all the time. For those with SWGs, the lower TA helps to keep the pH from climbing quite as fast.
2. SWG and chlorine raise the pH, but for different reasons. The SWG (aeration) and the chlorine (it's own pH level). Of course with liquid chlorine the pH will eventually fall back to where it was once the FC level drops a bit. For us SWG owners, the aeration occurs at every run cycle, so again we keep the TA a bit lower. I find that a TA of 50 - 60 works well with my pH. I may eventually need to increase the TA a little over time, but not too much.
3. Remember that industry levels are generic and do not account for all pool types, equipment, or situations. The TFP levels account for more than you may realize at first. For CH, as long as you are in the wide area of acceptable CH you will be fine. Keep in mind our FG pools are not made of calcium, so a low CH is generally not a problem. Don't go any lower than about 100 though to protect from stains. Too high (especially with a high pH) and you can still get scale like any other pool. For SWG owners, we find that the elevated CYA helps to protect the FC better throughout the day, especially in July - Sept when the sun is high over the pool.

The link below is my favorite one-stop shop for TFP info. I hope that helps address your questions. If we missed something, let us know.

 

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