Confused (FC decrease)

tcat · Sunday at 11:17 AM

Things have been good (clear) until about a week ago. Been keeping my CYA 40-50 (now closer to 40). FC at 3.5-4. All of a sudden it's dropping to 1 in 12 hours (with SWG set 2 LEDs higher than normal). When I check CC, it's always below .5. My CSI is always 0 to -.5. Going to HD to buy 6 gallons of LC. Is it worth buying their HTH phosphate remover? No clue what mine are, but I've never bothered with it.

Going to slam and check OCLT. I had to do this several years ago, but I always find it odd when it just comes on out of nowhere. Could it be the terrible oak pollen season just ending?

Jimrahbe · Sunday at 11:29 AM

T,

When my FC consumption goes up, it is almost always a sign that my CYA is too low... A CYA of 50 is too low for a pool in Texas... At least, it is for mine. I run a CYA of 60 to 70..

Don't do a SLAM unless you fail the OCLT..

Since the CYA test is pretty subjective, a reading of 40 could easily be just 30..

I suspect that increasing your CYA will 'fix' your problem.. :mrgreen:

Thanks,

Jim R.

tcat · Sunday at 11:40 AM

Jimrahbe said:
T,

When my FC consumption goes up, it is almost always a sign that my CYA is too low... A CYA of 50 is too low for a pool in Texas... At least, it is for mine. I run a CYA of 60 to 70..

Don't do a SLAM unless you fail the OCLT..

Since the CYA test is pretty subjective, a reading of 40 could easily be just 30..

I suspect that increasing your CYA will 'fix' your problem..

Thanks,

Jim R.

Your right! Hadn't checked CYA in a week or two, closer to 20 now! Not sure how it dropped that far, but time to add to get to 50-60. I'll run OCLT tonight before adding, much less chlorine required if it does need slam.

tcat · Monday at 7:58 AM

FC 8.0 at 8 pm (I had added a gallon of LC 6 hours earlier), 6.0 at 7 am. CC still lower than .5. Off to buy more LC...

Jimrahbe · Monday at 8:42 AM

Tcat,

It is almost impossible to get algae, with a saltwater pool... :scratch:

I could be wrong, but it appears to me you are trying to keep your FC as low as possible...

I believe in keeping my FC at or above my target 24/7, even in the winter, when the cell is not working..

Not sure what else it could be, but we are not too far apart weather wise..

I do run my pump and cell 24/7, at a low rpm...

Until recently, I owned three pools.. They were all run the same way, for well over 12 years.. In all that time, I never once had algae, and I am almost ashamed to say that I have never done a SLAM...

Thanks,

Jim R.

tcat · Monday at 8:58 AM

I check CYA in April and make sure it's at least 50. I have kept my FC at 4-6 up until it started going down. My salt cell is new and seems to be producing (no error lights). I'll bring CYA up to 40 today and do another OCLT tonight. My pump was off after last night's test, so this morning may have been inaccurate, I'll run it tonight. Have had nothing but clear water. Algae would seem odd.

tcat · 2025-05-20T09:36:10-0400

Well, added 4# CYA yesterday, it's 40 today. FC only dropped 1 last night. Added 3 more pounds today. I never realized FC went down so fast with low CYA. I also didn't think CYA decreased so much over a couple months. I only backwashed once. Guess CYA needs to get checked more than once a year!