New pool owner CYA is driving me crazy

May 16, 2017

Me and my wife purchased a home with a pool and it's my first pool that I have to maintain.

With that being said I have done countless hours of research and can't seem to figure the whole CYA deal out.

When I first started with the pool the numbers were off the charts and the local Leslie's pool supply said drain and start over.

So that's what we did emptied and refilled added a bag of shock and a few other things I can't remember and our pool was up and running crystal clear and CYA was at 30.

Fast forward 7 months and pool is still crystal clear but the CYA is steadily increasing. After finally figuring out that's it's caused by the tabs I'm floating I switched to 12% liquid chlorine.

The CYA is obviously staying put at 50 but I can't seem to dump enough liquid chlorine in the pool to keep it at the 5ppm recommended.

I have talked with several people and I am seriously convinced it's impossible to keep chlorine levels in spec while not using tabs to maintain or not to be dumping liquid chlorine in every two hours.

So what is the magic system here that I am missing, pool is crystal clear!

Thanks in advance.

Plaster Pool
Sand Filter
12,900 gallons

PH 7.5
TDS 600
CYA 50
Phosphate 0
Calcium 250


LifeTime Supporter
TFP Guide
Jan 18, 2015
Bunbury, WA, Australia
Welcome to the forum!!

From what you describe you may have an underlying algae issue. The problem is that as you increase the CYA level you need to maintain a higher FC level to keep the dreaded algae at bay as per this FC/CYA chart. It doesn't take much to drop below this level or for very long and once it takes hold you constantly battle to keep your chlorine levels up. By following the SLAM procedure you can eradicate the problem by raising your FC up to a relatively high level and then maintaining this level usually for several days to knock it on the head.

We also don't like to rely on pool store testing which is what I am assuming your test numbers are from. Getting one of the recommended test kits will help you either the TF-100 or K-2006C is the way to go

Try starting at Pool School and read some of the article around what TFP is about.
May 16, 2017
Thanks Jezza,

Sorry forgot to clarify on some things:

I do have my own test kit as well as CYA test kit.

All winter here in AZ wasn't a concern keeping chlorinyin the pool.

Now that we are in the summer the chlorine is obviously being burnt up do to larger evapotion rate.

Not sure about having algae in the pool both with the look of the water condition as well as zero phosphates.

I have read through all the pool school chapters.

Thanks Heath

- - - Updated - - -

Also noticed I didn't give alkalinity.

Alk: 80


Gold Supporter
Platinum Supporter
LifeTime Supporter
TFP Guide
Jul 16, 2012
Central MD
HK - Jezza has you headed in the right direction. Please post the test kit you are using. It's the key to the science. There is no magic. Once we identify the test kit, we can proceed.


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

No real magic here... if you add liquid chlorine to your pool it has to go somewhere. Either the sun or algae will consume it. Most pools use about 2 to 4 ppm per day.

A quick test you can do is called the OCLT... you basically wait until after sundown, add chlorine and wait for 30 minutes and test the FC level. Get your rear out of bed, before sunrise (sorry) and test the FC level again. If you lose less than 1 ppm of FC overnight than it is a good bet that nothing is in the water is eating your chlorine. If you lose more than 1 ppm then you have algae.. Pretty quick and simple test.

Here are the exact directions...


Jim R.


Well-known member
Oct 7, 2016
I'm over in Gilbert with what looks like a nearly identical set of pool stats. See my signature line.

My CYA is around 50 and I have no trouble maintaining a 6 ppm CL level. This time of year I'm adding maybe 30-40 oz of 10% bleach per day.

Be advised that you can have a clear looking pool and yet still be battling some type of low-level algae growth. Do the Overnight Chlorine Loss Test (OCLT). That is a great way to learn if you are losing too much chlorine to algae because it takes sunlight out of the chlorine loss equation.


Active member
Mar 27, 2017
Leander, Tx
I'm new to all this as well. So just a couple of comments from one new guy to another. I thought I had clear water as well. Turns out I really didn't know what clear water looks like. Anyway, It took me a while a first to handle on the chlorine levels and I'm convinced I had the very beginnings of an Algae problem just waiting to bloom on me. I got one of the recommended test kits and after getting my CYA into an acceptable range, at first I was using quite a bit of chlorine but after a week or at the correct target level or a bit above things evened out. I probably should have done a SLAM but I think I caught the problem early enough that beginning at target level or above it was able to catch up to the problem and eradicate it early enough. I didn't really know what I was doing at the time, but I feel like I have a handle on my pool now and although chlorine use is increasing slightly due to the sun I can fairly accurately predict my chlorine levels and addition requirements. Right now I'm using around 64oz of 10% on a sunny day. With CYA 70 and a target of 8-10 FC. I'm not 100% confident of my CYA reading but I'm pretty confident it's either 60 or 70 so I go with the higher number to be safe.
May 16, 2017
So my understanding is with zero phosphate algae has nothing to grow or live on or am I missing something?

I will do the chlorine use test as pointed out and see if there is something going on there.

Just get so frustrated with 10 different people having 10 different answers. I just want to have the solution so I can enjoy our pool rather then chasing my tail.

It can't be that hard can it. I mean I can keep a saltwater reef display going but I can't seem to balance a pool to save my life :)

Thanks again for all that have had input!



Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
Aug 10, 2012
Nope, not true about phosphates. The way to keep a pool algae free is to always maintain FC above minimum for your CYA, [FC/CYA][/FC/CYA]. I keep mine at target or above at all times. When FC drops below minimum the pool is unsanitary and algae can grow. With or without phosphates. Algae can consume phosphates as a food source but all plants primary food source is photosynthesis. We don't even recommend testing phosphates. I'm on my sixth swim season and I've never tested phosphates in my pool.


Silver Supporter
Aug 23, 2012
S. Louisiana
^^^^^ what he said...and he is the man.

if you really look back at your thread, everyone is really on the same page. it's all a chlorine cya balancing act, and everyone has different pools, parts of the country, equipment...

you're already a pool expert, you just don't know it yet :cool:


Bronze Supporter
LifeTime Supporter
TFP Guide
Jun 3, 2015
There are not 10 different answers, only one, and it is chlorine. Your FC should never ever drop below 7.5% of your CYA or algae will be able to grow.

Perform the OCLT. It will tell the tale.....


LifeTime Supporter
Aug 10, 2013
Arab, Alabama
And to can't perform the OCLT without a good test kit! Only two exist...TF-100 or the Taylor K2006, if you are using some other kit it will be next to impossible to help.
May 16, 2017
I appreciate all the responses, I have order the K2006C kit so time will tell. I will keep the chlorine as the CYA chart says.

Do you guys run floating chlorine?


LifeTime Supporter
TFP Guide
Jan 18, 2015
Bunbury, WA, Australia
Good job on the K-2006C- you won't regret it.

Most of us don't run floaters and add in CYA separately. The problem with floaters is that they continue to add CYA to the water until the levels become unmanageable. The only practical way to then reduce it is to drain some of the water in the pool.
May 16, 2017
Well sorry for the long delay but I am back with some numbers, I actually ended up with the TF-100 kit!

PH-8.2 needs acid
Borate-0 Wanted to test as I plan on adding

let me know thoughts of where I need to go from here, thanks in advance!


Mod Squad
May 3, 2014
Laughlin, NV
Good Job on the test kit!
Round up the CYA to 50.
Follow the FC/CYA chart for normally chlorinated pools (I assume you do not have a SWCG - filling out your signature would help us help you)
Put your test results into PoolMath and look at your CSI. A very important number to us here in the land of high CH/TA fill water with high evaporation rates.
Keep your CSI between -0.6 and zero. You will find by lowering your pH to 7.2 with muriatic acid you will slowly lower your TA which will assist greatly with your CSI.

Most likely this winter it will be time to drain and start over as your CH will be near or over 1000ppm and it will become increasingly difficult to keep from scaling.

Good luck!