Some questions on the CYA/chlorine chart

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Newguy209

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Aug 8, 2018
5
Riverbank/Ca
Well I got rid of my pool guy after 3 months because all they were doing was literally dumping in a bunch of chlorine to last from week to week. I watched on the camera and timed him. The guy was literally here 2 minutes. There's no way he was able to test the water chemistry and calcualte what he'd need based on those results in two minutes. They'd bump the chlorine levels up to 10 so it would last until the next week when they came. Problem was my pH was 8.2 and my Alkalinity was 180 so they weren't doing anything with that. I even tested it several times in the day they would come when the chlorine would drop back to normal levels of 4 or so, just to make sure the high chlorine levels weren't messing up my tests.

Anyways, I've got everything back in check over the last couple weeks.

FC-3.8
CC-0
Ph-7.5
Alk-100
CH-250
CYA-55

So here is my problem. They added a bunch of CYA when they first came out. I'll be honest I didn't even know what that was and hadn't added it to the pool in the 2 years I've had it. I just added the chlorine tabs and kept chlorine and other stuff levels at the normal with strips and called it good. I had never added MA, baking soda, etc.

I've read through all of the Pool School, learned a bunch, and got my water balanced using my Taylor K-2006C. One thing I'm curious about though is the CYA/chlorine chart. With my CYA levels where they are, it's saying I should be all the way in the 6-7ppm range on my chlorine. Everything I've read to date says not to even let people in the water with anything over 4ppm and that it's not safe to swim in. Then every pool place I've spoken with says my CYA levels are right where they need to be.

I really don't want to have to drain my pool now that I've worked so hard to get it balanced, just to knock the CYA levels down. I also don't want to keep my chlorine levels so high. Even if I did keep the chlorine at 6-7, would I be going through more chlorine to keep it that high vs if I had it at 3-4? I would assume that the pool is going to use it up at the same rate no matter what level it's at.

Not sure where to go from here?
 
:wave: Welcome to TFP!!!

Follow the [FC/CYA][/FC/CYA]. It is perfectly safe. The "Do not go in over 4ppm" is based on 0 CYA. The CYA acts as a buffer and a lot of the pool industry still ignores that relationship.

Your CYA is fine, just keep the FC above the minimum listed in the [FC/CYA][/FC/CYA].

The CYA will protect your FC from the sun so your losses should not go up at the higher FC. In fact, you will use more FC if you keep it too low, because algae is going to start and consume it and then you have to SLAM again.

FYI, it is safe to swim up to the shock FC level listed for your CYA. At that level, the active chlorine (harshness) is still less than a pool with 0ppm CYA and a 1ppm FC.
 
^ What he said.

I have the same level CYA as you -- and actually you always round up to the nearest 10 when using the CYA chart, so use 60 as your CYA level. For California, CYA of 60 is okay.

I adjust my FC up to 8 ppm each evening, and it's usually down to around 6 by the next evening when I test and adjust again. The water in my pool feels great, and there are none of the smells or other issues people associate with high chlorine levels.

Also, I don't think they added CYA -- the CYA you have came from using the chlorine tablets, which have CYA in them. You are lucky it isn't higher. So stop using those tabs, because you really don't want to go above about 60 ppm on the CYA. Switch immediately to liquid chlorine.
 
Hi, and welcome to TFP!
Man, your CYA is just fine.
I agree 100% with blizzle.

When working with science, you cannot look at a specific number as the answer. Many things in chemistry change (such as CYA levels) and other things, and these are variables and change frequently and when they do, then that Number must change also. So whats the way to solve the equation?

So with respenct to FC, you have to look at it as a percentage. Lets compare TFP to Pool Industry recommendation using percentage. Recommended FC level = FC/CYA

On the TFP chart The Recommended FC is 11.5% of the CYA, the minimum is 7.5% of the CYA for non-saltwater pools.

The pool industry recommendations is FC 3 and CYA 30. Guess what the answer of FC/CYA is? Its 10%

So up to CYA 30, the pool industry and TFP are pretty dang close with their recommendations.

But thats where the pool industry stops. After all, if the cat got out of the bag to maintain FC at 10% of whatever the CYA is, then everyone would have lovely pools and the pool folks would be out of the business of selling miracle cures.

We recommend a higher CYA because Chlorine wont last long in an outdoor pool with steady UV from the sun with a 30 CYA for non-saltwater pools. The CYA helps shield FC from those UVs that burn it off. So higher CYA (up to a point) means less consumption of FC which means a few more pennies in our piggy bank.

So keep this % factor that we call the FC/CYA ratio in mind and that it needs to be maintained for chlorine to do it's job.

7.5 to 11.5% (and 10% is a good rule of thumb and makes the math easier!).
 
Thanks for the info. I need to make a trip to the pool store I found that has a returnable chlorine jug/exchange system going on. It's a mom and pops store that's been around for almost 40 years. I'm trying not to be throwing away a ton of 1 gallon chlorine jugs every week. I'm not a treehuger by any means, actually the complete opposite, but I try to do my part where I can. Only problem with that is I'm paying $1 more per gallon vs buying from home Depot. I need to find out if buying in bulk(maybe 10-15 gallons at a time) will lower my cost. At the pool store it's $18.80+tax for a 4 gallon crate. Not sure how many I'll go through a week but this seems way more expensive over the tabs that I don't have to add more than once a week in the summer here in California. I've already called HASA to see if they had a refill station nearby but I guess good ol California doesn't allow that like some other states do. Only if you have a business license, youre able to from what I was told.

Also, will have my free chlorine in the 7-9 range make my test kit results innacurate?
 
JoeSelf said:
Not with the drop based FAS-DPD test, it can test up to 50. If FC is over 10, then PH test is invalid. Will show high.
Click to expand...

Ok so last night my pH was about a 7.6-7.7. I added one gallon of 10% chlorine from Home Depot to bring my chlorine levels up to match the CYA level. So I checked my water right now and the FC is sitting at 8.6 but now my pH is showing higher than the 8.0, so I'd guess maybe 8.2.

Should I add MA to bring it back down or do you think it's reading high because of how high my chlorine levels are?

I'm begging to feel like this is an ongoing juggling act.
 
Your ph test is accurate with FC below 10 ppm.

Your TA is quite high. It is driving your ph rise. Continue to lower your ph to 7.4 or so each time it reaches 8. This will eventually lower your TA.
 
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