Not generating enough chlorine

[Sailracer]

I have really been struggling with my SWG this year. I have never had problems before, but this year I have not been able to keep my chlorine levels stable. I SLAMmed the pool about a month ago and went up to the mustard algae shock levels just in case there was any of that around. I scrubbed out my light niches, backwashed, etc. The pool passed the OCLT and had no measureable CC. Once that was achieved I started raising my CYA from 30 up to 65. After a few days when the FC dropped down to the 12 ppm range I started working on setting the run-time for the SWG. I found that running it at 100% for 12 hours a day was not enough to maintain the chlorine levels. It is now about a month later and I am still having to run the SWG at 100% for about 18 hours a day to maintain FC in the 7-8 ppm range. I noticed my PH is drifting up fairly quickly. After reading on this forum, that is probably because I am running the SWG for so long. TA was 120 several days ago. I have been adding muriatic acid to knock the TA and PH down and will continue to do so, but would high PH and TA cause increased chlorine demand?

Yesterday had a surprise. The FC dropped from 7 down to 4 and CC went from 0 up to 1.5ppm (the pool was only lightly used and it was a mostly cloudy day). What could cause that? I had not seen any measurable CC since completing the SLAM. Could the muriatic acid cause that?

This is probably a good point to show my numbers from yesterday after adding a gallon of muriatic acid:

CYA: 65
PH: 7.1
TA: 110
FC: 4
CC: 1.5
CH: 100 (need to work on bringing this up)

Should I try another OCLT to see if there is something in the water using up all the chlorine? It looks like the generator is working- I see lots of cloudy water coming off the cell. Also, the solar panels are new to my system. Could the extra 4 or 5 degrees they are adding to the water over previous years increase the chlorine demand by that much? In the past I have only had to run the generator for 11-12 hours to maintain chlorine levels. Is trying to maintain the level at 7ppm harder than trying to maintain it at 4?

Thanks for any help or ideas.

 

[Sailracer]

I may have answered one of the questions. I just rechecked the numbers this morning and FC was back at 8.5ppm and CC was 0. Either the muriatic acid caused a low reading last night or there was some other contaminant in the test tube. So back to the original question- why do I need to run my SWG so long?

The RJ45 SWG is claimed to output 2 lbs of Chlorine per day. Using the pool math page, that would be enough to raise my FC from 7 to 16 in 24 hours assuming no usage/UV losses, yet I can barely maintain an FC of 7 with 18 hours of running. Does that sound like excessive chlorine usage?

 

[pooldv]

That is a bit high FC usage for a day. Have you done an Overnight Chlorine Loss Test?

When things are a little fishy in my pool I'll raise FC to about 50% of shock level, [FC/CYA][/FC/CYA], for a couple of days and brush a little extra. It clears up any sipuspicious activity. You never know if some critters had a party in your pool all night. Or there was a duck drive by or something. We have a fair amount of animal scat on our pool deck and coping most mornings. Especially when it is HOT! They like to hang out by the watering hole.

Raising your cya up to 80 will also help with your daytime FC loss to the sun.

 

[Sailracer]

I have been afraid to shut off the SWG for a night to do the OCLT again since I need a lot of the run time at night to keep the chlorine up. Maybe I'll try it tonight just to be sure the chlorine level is stable overnight.

 

[pooldv]

Grab a few jugs of bleach at the grocery store as insurance. I get store brand at Kroger, 8.25%, plain unscented. A jug will add about 3 ppm in your pool, 4ppm in mine. Add a jug or two at 8-9pm, let the pump run and test FC 30-60 minutes later. That way there is no risk of FC dropping below minimum.

I always keep 4-6 jugs of bleach around to add before/after big swim days, when things aren't quite right or to raise FC before going out of town. I find it easier to add a jug or two of bleach than to constantly try to tweak the SWG output.

 

[Sailracer]

Overnight chlorine loss was 0 last night. I ran the SWG and pump for 15 hours yesterday during the day and it raised the FC by 1 ppm to 9, so that seems to be an improvement over where I was, but it still seems like I am using a lot of chlorine during the day. Could all of that loss be from sunlight? Will going from 65 up to 80 on my CYA make that much difference?

 

[pooldv]

That is good news! Yes, it will make a big difference going from 70 to 80.

 

[Sailracer]

OK. CYA is now at 80. I'll see how this week goes- it's supposed to be sunny and warm.

 

[Sailracer]

It seems like the CYA at 80 has made some difference. I ran the SWG at 100% for 10 hours a day for the first couple days this week and the FC crept up slightly from 9 to 9.5 PPM. I lowered the SWG to 70% 3 days ago and the FC has drifted down to 8. I just upped the % to 80 and I'll see if I can slowly drift down to a target FC of 6 and then bump the % up to 90 or 100 to stabilize. It will probably stabilize just in time to close the pool for the fall

Does that still seem like high chlorine demand?

Thanks!

 

[Vickery]

Does your RJ45 have the clear cell? If so have you examined it for any scaling that would reduce the output?

 

[Sailracer]

Yes, it is the clear cell. It had very little visible scale on it, but I cleaned with muriatic acid anyway about 6 weeks ago.

I've noticed the RJ-45 seems to spend a lot of time testing these days. It seems like 3 out of 4 times when I go to check on the pool equipment it is running its salt test. It may just be coincidence, but I wonder if there is something that governs how often it runs the test and the frequency of testing could give a clue to something being wrong.