New to TFP -- having difficulty maintaining FC

[Jdhaenen]

I've been lurking on this forum for a while. I purchased a home in South Florida with an existing smaller 7.5K gal gunnite pool about 1 year ago and have never owned a pool before.

Last summer as a newbie I was trying to maintain the pool with trichlor tablets in a floater. We had some algae issues, especially if we'd go out of town for a while. It wasn't terrible but wasn't great. We occasionally used some algaecides and clarifier.
Our local pinch a penny sold us some 2.5 gal containers of liquid chlorine to use a shock and over the winter I ditched the tri chlor after learning about CYA and seemed to have no issue maintaining the FC with additions of liquid chlorine every few days of maybe 16oz.
CYA was 100+, not sure of the exact number. Our pool gets a lot of full sun in summer months, in the winter due to the trees on the south side we don't get much sun.

Fast forward to this summer, once the sun got more intense I was having difficulty staying on top of the FC, was using more than a quart daily even with the high CYA. It would drop fast during the day. Also I had discovered this site and being kind of a geek thought I would try to use the methods on this site.

I bought a Taylor FAS-DPD kit, a Stenner Econ injection pump (4.5 gallons capacity, variable speed, with 7.5 gallon tank) that I got set up. I wanted a pump so I could maintain chlorine even when we are out of town.

I emptied a lot of water to bring CYA down to 30 as confirmed with the test kit (and pool store). Balanced everything, did the SLAM. I had to use a lot of chlorine to keep it at the recommended level for my CYA during the SLAM, at least a gallon daily. I had cranked up the Stenner pump during the SLAM to keep the level high and turned it off at night.

I've never had an issue with CC for the entire time I've had the pool, always has been less than .5. I did SLAM for a couple days, I wasn't having an issue with the nighttime test or CC so didn't do it any longer than that.

Since then my water has looked beautiful, I have no issue maintaining my pH and haven't needed to add anything except chlorine. It didn't seem to solve my problem that my pool burns so much chlorine during the day. I'm aiming for about FC=4. I'm adding about 32oz daily with the Stenner but sometimes still need to add more manually. Chlorine is fresh from pinch a penny and does what it should to my FC number but it just doesn't last.

I've started dropping a tri chlor tablet in the skimmer now and then to bring up my CYA. When I do that it seems to maintain better for some time.

Is this a normal amount of chlorine to add daily? 32 oz means I am losing all my chlorine daily. I do get a lot of sun now, pool temp gets up to 90 degrees. I have an in floor cleaning system which moves a lot of water around so maybe it's giving the water more sun exposure. Also the pool has a large shallow sun shelf and the floor cleaners blow a lot of water across the floor there.

Right now my FC 4, CC under .5, pH 7.4, TA 90, CH 180, CYA 35

Curious on opinions if I should try SLAM again, or keep moving the CYA up, or if my chlorine consumption is just normal for my environment.

 

[Mike1162]

CYA of 35 is probably not high enough for a sunny pool in Florida. I'm going to guess you should be around 50 but wait for someone else to give you a recommendation.

 

[Dtkokay]

+1 to increasing your CYA to better protect your chlorine. I would go to 50 on CYA, and be sure to increase your FC level according to the CYA / FC chart on this web site.

Also, I get the sense that you are maintaining your FC at the minimum required level. That doesn't give you any room for error. I try to maintain my FC at the upper end of the recommended range for my CYA. Having too much FC is not a big deal. Having too little can lead to algae, as you have seen first hand.

 

[bmoreswim]

Using 2-4 PPM of FC per day is normal. Agree with the above on a higher summertime CYA level. That makes FC last longer and requires a slightly higher FC level to be maintained. My FC is always at the high end of the range. It's just how I roll. I never worry about it getting too low then.

 

[PoolNewb2020]

Welcome to the forum!
It's good to see you figured a lot of things out already.

However, I'm more inclined to think that your FC of 4ppm has something to do with it. The minimum FC level for CYA of 40ppm is 3ppm, so you are riding very close to the minimum and with daily swings you could go below between additions. You may still have a small amount of algae that eats your FC.
I would perform an OCLT and go from there. Overnight Chlorine Loss Test (OCLT)

As for FC level, try to keep it on the high side, which is 7ppm for CYA of 40.
For reference here is the Chlorine/CYA Chart, it's one of the most important tools we use to keep a proper free chlorine levels in relation to CYA levels.

 

[Jdhaenen]

Thanks for the responses. I plan to bump up my cya, but in the meantime I did another SLAM and bumped up my stenner output. Actually the pool is looking amazing even better than when I thought it was good.

I’m going to back the Stenner down slowly every couple days until I’m at the high end of the recommended level, maybe about seven. It was at 13 and has drifted down to 9 with adding about 1.8 quarts of liquid daily which is 7.4 ppm. Still seems like a lot but if that’s what works I’m ok with it. Hopefully it will get better with more cya.

 

[Chasarms]

When you have FC at slam levels, it will degrade more quickly from the sun’s UV because there isn’t enough CYA to protect it at those levels.

You should gauge FC losses based on your experiences with FC losses at maintenance targets. 4ppm per day of loss to UV is not outside the norm.