Puzzled..... periodic slight cloudiness, despite SLAMs & high-ish CL levels

[Chris_in_FL]

Greetings! I've appreciated all the great info on this site for ~4 years now.... kudos to everyone! I'm wondering what the cause(s) may be for recurring slight cloudiness. This happens each summer here in Florida (pool temp in the 80s). I've SLAMed many times, adhering to the SLAM guidelines. (Taylor test kit w/ DPD, check FC level 3-4x daily, OCLT test and clarity pass, etc...) Almost without fail, within about 2 weeks of SLAMing, the water begins to get slightly cloudy again... despite testing every 1-2 days & keeping the FC level at 6-7ppm after SLAMing. (I do mean SLIGHTLY cloudy - I bump up the FC level w/ liquid Cl, or SLAM, or shock with potassium monopersulfate when the water strays noticeably from being sparkly clear.)

I brush & vacuum the pool roughly weekly, year-round.​

Again, I'll affirm that I've followed the SLAM guidelines scrupulously. (I'm retired... got lots of time to obsess over the pool, and am familiar with chemistry.) I wonder if perhaps our water feature is the culprit. We have a stack-rock waterfall along 2 sides of the pool (about 22 ft wide total, and 2 ft high), which has a zillion crevices where crud might hide. I run the waterfall daily for up to 1 hour. I've sprayed it every few weeks with 3-4% chlorine. I've run it for a couple of hours during SLAM... brushed the heck out of it during SLAM... done everything but performed an exorcism. The one thing I haven't done is use algaecides (or add borates).

Thanks for any insights or suggestions!! I'm resigned to keeping the FC level up around 7-8ppm, and occasionally using oxidizing shock if needed. Today's readings (which are pretty typical):

FC: 7
CC: 0.5
Ph: 7.6
TA: 85
CH: 350
CYA: 80
Temp: 85F

• 10,000 gallon, IG w/ pebble-tec & tile (includes both pool and attached spa)
• All Hayward: DE filter, NorthStar 1.4HP single-speed pump, H350 gas heater
• T15 Hayward SWG w/ prologic control
• Hayward Tri-star 1/2 HP single-speed pump for waterfall
• Taylor k-2005 test kit w/ DPD
• Screen enclosure over pool. Filled w/ town water as needed.

 

[Chris_in_FL]

Should have mentioned... We run the filter for 7-10 hours/day, depending on the water temp. Typically 5-7 hrs during the daylight, and 2-3 hours starting around 12AM. There's generally minimal fluctuation in the FC level throughout the day/night. Filter & SWG cell are well-maintained. Cheers!

 

[mknauss]

Do you use a Taylor K2006 kit or the pool store? Your signature says pool store ...............

Keeping your FC well above minimum is a good idea.

 

[Chris_in_FL]

Sorry - old signature, from before I became addicted to testing & using DPD for FC tests. I test myself w/ Taylor kit every 1-2 days. (I also go to the pool store, but just use their info as a sanity check for CYA, CH and TA.... that I test myself ~weekly). There are a couple of good folks there, and some newbies who's readings are suspect.) Tnx for the quick response!

 

[Chris_in_FL]

One thing I worry about ("worry" is probably overly strong), is whether keeping FC high... like in the 7-8ppm range will seriously shorten the life of our brand-new Hayward heater, and anything else that's metallic. So it would be nice to find a 'real' solution, so we could enjoy a pristine pool with FC closer to 4. Cheers!

 

[mknauss]

Low pH will harm your heater. Not chlorine.

 

[Chris_in_FL]

True. But I figure since chlorine is a good oxidizer, it also attacks metal. Anyhoo.. it'd be nice to find that I've been a bonehead and missed some explanation for the underlying issue.

 

[Pool_Medic]

If your swg is plumbed after your heater you will have zero issues. That 80cya buffers the chlorine. I keep my pool at 10 chlorine for over 15 years, not one issue but crystal clear water. ?

 

[Danforth]

Not sure if this helps, but you mentioned performing multiple SLAMs. When you performed the SLAM procedure, you lowered your pH at the beginning. Which leads me to the following thought:

I have noticed in my pool that as pH drifts toward the high end, the water seems slightly dull. I wouldn’t call it cloudy, but such things are subjective, of course! After adding acid and lowering the pH, it gets super sparkly again. Could this be what you are experiencing?

 

[Chris_in_FL]

Hi Danforth. The cloudiness appears to be unrelated to Ph. But I'll keep an eye out for that, just to be sure. Poolmedic - Tnx for the comment. The SWG cell is plumbed as it should be - just before the returns. Agree that high CYA reduces the effectiveness of the Cl. (I've wondered if it also reduces the oxidizing effect... assume that it does, similar to the effect on sanitizing, but would welcome confirmation.) What I was thinking about is the normal background FC level being high... not the super-high Cl level after the salt cell.