Salt water pool which gets little to no sun not holding FC - Excessive chlorine required to SLAM

[jc259]

Over the last few weeks I noticed a slight cloudiness to the water in our 13'-11,000L (2905Gal) above ground salt water pool (Water was new this year in May). I thought the slight cloudiness was because I have a 20ft blue tarp that is over the pool area (which was new this year and blocks out most of the sun), but it looks like it was a water quality issue. This last week the salt water generator seemed to stop working or was just barely producing any chlorine so I had turned it to run longer progressively and was getting to the point I thought it was broken.

Today I confirmed the SWG is actually generating chlorine by taking water right off the return with a hose and testing it. After some reading on here I decided I would SLAM the pool today even thought the water looked pretty much clear at this point with no algae growth in the pool at all. Basically looking at the water and the levels everything seemed great other then it wouldn't hold FC. Before I started the SLAM this afternoon FC 0, CYA 30, PH 7.2, TA 120, CH 280, salt 2840, temp 84f.

1) 4:00pm Added 500ML of 10.6% bleach - FC after 1.5 hrs was 2.5 (right here I was confused as I expected it to be much higher)
2) 5:30pm Added 500ML of 10.6% bleach - @6:27pm FC 5.0 - @7:20 pm FC 4.0
-Went to pet store and had water tested for Ammonia - showed little to no Ammonia at this point
3) 7:25pm Added 600ml of 10.6% bleach - @7:45PM FC 9.0 - @8:07PM FC 7.0 (I think the pool water is looking slightly clearer then it was earlier today)
4) 9:32pm Added 500ml of 10.6% bleach - @10:30pm FC 9.0 - CC under 0.5 as I was using 10ml FAS-DPD test
5) 10:30pm Added 600ml of 10.6% bleach - @11:30PM FC 11.5 - CC under 1 accidently put two drops in before swirling it.

I did check for CC a couple times earlier in the process and it was always below 0.5 but was using 10ml sample.

Does it make sense I have dumped 2.7 Liters of 10.6% bleach into 11,000L (2905 Gal) of water and my FC has only got to 11.5 even though the water looked pretty much perfect this morning? Could there be something else causing the water to not hold the FC?

I'll post more as I go.

 

[Texas Splash]

Does it make sense I have dumped 2.7 Liters of 10.6% bleach into 11,000L (2905 Gal) of water and my FC has only got to 11.5 even though the water looked pretty much perfect this morning?

With algae, yes. That's the initial drop from all the contaminants. In the early part of the SLAM Process, you often times have to add chlorine more frequently. Once the chlorine overtakes the organics, it should stabilize. For now, watch it closely and keep the FC up to "12" which is your ideal SLAM FC level. Over time that should hold better. Follow all the SLAM protocol and maintain that FC level until you pass all 3 SLAM criteria. Good luck.

 

[jc259]

Thanks for the response. This morning my testing shows the following, Is it normal for such a large drop over night?
6) Day2-8:31am FC 4 - CC under 0.5

I am wondering if I am better off to just use some Dichlor to get past this since my CYA is only 30. I am planning to replace some water anyhow to try and bring my Calcium down as well in the next bit. Would it make sense to do this in one day vs SLAMing for potentially days?

Another option: If we are not going to swim in it, could I just go to a higher level of FC like 15,20 or 30 to try and get the chlorine to take over the organics using liquid chlorine?

Appreciate any feedback

 

[Texas Splash]

A CYA of 30 is perfect for the SLAM because it requires the least elevated FC level of 12. But if you wanted to change water now to lower the CH, go ahead. Put the SLAM on pause while you exchange water. Then rebalance and ensure the CYA is back to 30 (you'll need to add some) then resume the FC level of 12. With a CYA of 30 and FC SLAM level of 12, there is no need to go over the 12 number. It will not speed up the SLAM and will only result in a waste of chlorine with not enough CYA to adhere to during the day.

 

[jc259]

Thanks @Texas Splash. In my case where I have a cover over the entire pool area, ie zero direct sunlight, does having CYA in the pool do anything or is it unnecessary?

 

[Saturn94]

Thanks @Texas Splash. In my case where I have a cover over the entire pool area, ie zero direct sunlight, does having CYA in the pool do anything or is it unnecessary?

In addition to protecting chlorine from UV light, CYA also makes the water much more gentle on skin and eyes, hence why TFP also recommends adding CYA to indoor pools.

 

[jc259]

Took a few days but the FC started holding. I also realized my CYA was way down. I thought it was close to 30 as the dot was just visible when the tube was full but it was actually way down. I have it around 40 now so it's easier to gauge when looking in the tube.