Multiple SLAMs with in 13 days. What am I doing wrong?

[joshlarsen]

If you don’t want to read a book about how I got here feel free to jump down to “The Problem” section. In short the history is that I had just performed a SLAM and passed an OCLT 13 days ago.

The History:
Hey guys looking for some help. We’ve had water in our pool for about 90 days and after converting to salt I had several good weeks of chlorine levels and really only needed to add Muriatic Acid to keep my pool in balance. Then we left for 10 days over the 4th of July on vacation and I had a neighbor come and test the water while we were gone and my FC dropped like a rock right after we left. He also being a new pool owner added some tablets to the feeder and I kept cranking my salt cell up and up over the few days till we got to 100%. The pool never got any green spots or visible algae and the water looked pretty clear but when I got home, I dumped some liquid chlorine in and started an OCLT. Of course, it failed dropped from 9 to 3.6ppm. But not only my CYA had all of a sudden dropped from 65 to filling the calendar and still being able to fairly clearly seeing the dot at the bottom. No leak, no major splash out, no rain. So after some reading a bit I found the only other way CYA drops like that is by a bacteria converting it to ammonia. So I added chlorine a couple times over a 8 or so hour window and watched to make sure the chlorine wasn’t getting consumed really really fast and then added CYA to get to 30ppm and SLAMed the pool. For 3 days I tested many times a day and added liquid chlorine to get to 12ppm of FC according to PoolMath. The night of day 3 I did another OCLT and lost .8ppm of FC so less than 1ppm loss, CC was .2, and everything was what I though back to normal so I turned the cell back on a bit higher than I had before and started adding more CYA to get me back to 65-70ppm and planned to decrease the salt cell every few days to get my FC hopefully back down to a goal of about 4.5-5ppm which I did over a weeks’ time.

The possible cause of that first issue:
We had some step line tile in our SPA that the plaster guys put in while they were installing the plaster (Yes should have been done before they came). Anyways it was cooked and looked like compete Crud so I made the pool builder come back drain the spa and cut them out and relay the tile and the plaster guys came back and replastered around them. I think my chlorine/cya issue started by something they brought into the SPA with dirty boots or something because the spa refilled the day before we left on vacation and the chlorine loss started right after that. Its just a hunch but it’s the only thing that changed.

The Problem:
I’m back to having chlorine level issue again already. I did an OCLT last night and lost 1.4ppm between 11:21PM and 4:27AM and had added enough chlorine that should have gotten me to 8.7ppm at 2:34 in the afternoon. I started a SLAM again which will suck now that I have a CYA of 60ppm and have to have a higher FC now. What do I have to do to get out of this cycle? Did I possible not get everything killed the first time I did the SLAM or is it a second problem or is it possible one of the pool floats had algae in it or something?

I have been running the pump 24x7 at 1,100 RPM which according to the pump is moving 31GPM of water.

Full results from yesterday
FC: 0.6 (I have added chlorine, did the OCLT, and started a SLAM since this)
CC: 0.2
pH: 7.4
TA: 70
CYA: 60
CH: 310
SALT: 3200
Temp: 85F

 

[nobody291]

FC: 0.6

This is the main issue. The bare minimum FC using a SWG with a CYA of 60 is 3. I'd aim for 6 or 7 so that you have a buffer. Once your FC is allowed to drop below the minimum (even if it's just for a little while), you're giving algae (and other microorganisms) a chance to gain a foothold; and then the only resolution is to SLAM.

 

[zea3]

I don't think you got everything killed the first time around. .08 is pretty close to 1.0 I don't think I would have stopped the slam at that point. I would want .05 or below to say I passed the OCLT. I would bring the FC back up to slam level and try to keep it there as much as possible for 24 hours and then run another OCLT. The first time you bump it up to slam level check the chlorine and make sure you hit your slam target.

 

[joshlarsen]

This is the main issue. The bare minimum FC using a SWG with a CYA of 60 is 3. I'd aim for 6 or 7 so that you have a buffer. Once your FC is allowed to drop below the minimum (even if it's just for a little while), you're giving algae (and other microorganisms) a chance to gain a foothold; and then the only resolution is to SLAM.

Yes I am well aware an of 0.6 FC is a problem. It dropped there after the issue started. My SWG was set at 60% which should be more than enough to maintain a FC of 6 or more.

 

[Mdragger88]

I am with Zea, probably weren’t really done with slam the 1st time. SLAM ON!

For a successful SLAM Process you need to continue until you meet ALL 3 end of slam criteria-
You are done when:

CC is 0.5 or lower;
You pass an Overnight Chlorine Loss Test
AND
the water is clear.
(Crystal Clear w/no algae dead or alive)

*Check & scrub every nook & cranny where algae may hide (light niches, drain covers, ladder handrails, skimmer throats/weirs, etc.)
*Run slam level water through all water features & lines for at least a couple hours a day during the SLAM Process.
*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine)
*Backwash/clean filter when pressure rises 25%over clean pressure.
Once slam is complete u may want to do an overnight chlorine gain test to make sure your swg is operating properly & get cya up to 70-80.

 

[joshlarsen]

I don't think you got everything killed the first time around. .08 is pretty close to 1.0 I don't think I would have stopped the slam at that point. I would want .05 or below to say I passed the OCLT. I would bring the FC back up to slam level and try to keep it there as much as possible for 24 hours and then run another OCLT. The first time you bump it up to slam level check the chlorine and make sure you hit your slam target.

I am also thinking I must not have gotten everything killed the first SLAM. I thought I would be good because the OCLT doc said below a 1ppm loss you pass and then I kept it above an 8.6FC for another day and a half but I also started increasing CYA right after the first OCLT passed.

 

[joshlarsen]

I am with Zea, probably weren’t really done with slam the 1st time. SLAM ON!

For a successful SLAM Process you need to continue until you meet ALL 3 end of slam criteria-
You are done when:

CC is 0.5 or lower;
You pass an Overnight Chlorine Loss Test
AND
the water is clear.
(Crystal Clear w/no algae dead or alive)

*Check & scrub every nook & cranny where algae may hide (light niches, drain covers, ladder handrails, skimmer throats/weirs, etc.)
*Run slam level water through all water features & lines for at least a couple hours a day during the SLAM Process.
*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine)
*Backwash/clean filter when pressure rises 25%over clean pressure.
Once slam is complete u may want to do an overnight chlorine gain test to make sure your swg is operating properly & get cya up to 70-80.

When I completed the first SLAM I did pass all criteria I had a CC of .2, On my OCLT I lost 0.8FC and in the OCLT doc it says up to a loss of 1 FC, and the water was never green and always crystal clear. Its crystal clean now too. But I still feel I had to have had something left in the pool. While Shocking I did run the bubblers a while each day and also half cracked open the heater bypass just to make sure nothing was in those lines as well.

A chlorine gain test is a good suggestion and I for this SLAM I will run longer and will shoot for less than a .5 FC loss in the OCLT.

 

[Mdragger88]

Don’t overlook the nooks & crannies- it’s hidden somewhere…

 

[joshlarsen]

Don’t overlook the nooks & crannies- it’s hidden somewhere…

You got me looking and I'm thinking I may have found what I overlooked before. I dont think I actually got the SPA main drain flushed during my first SLAM. I just changed valves so its continually pulling/pushing water through all the lines and all the valves. So now I'll just have to make sure to run the bubblers on a regular basis during SALM to make sure those lines get shock level water through them.

I also have a line the builder installed for a pressure side vac that will probably never get used for that. Its open on both ends, one at equipment pad and one under water. Can I just pour some diluted liquid bleach down it and run a hose in it for a while a couple times a day to make sure nothing is living in there?

 

[zea3]

I think running some bleach through there is a good idea. When you brig the pool to slam level scoop up a bucket full and run it through that line.
Most of our members test FC using a 10 ml sample to save on reagent. You conduct the test and divide number of drops by 2 to get the result.

 

[Mdragger88]

What she said

 

[joshlarsen]

I just tested CYA and I lost 10ppm(From 60 to 50) from 4 days ago when I tested right before performing the SLAM. Should I continue using the 60ppm of CYA till I am done with the slam or trust the 50 and use that to determine FC level?

 

[duraleigh]

TFP needs to be consistent on it's suggested values. The OCLT maximum FC loss is 1.0 overnight. An overnight loss of .8 passes that test.

That OP is still having issues doesn't alter the requirement. That limitation of 1.0 FC loss has proven valid over time.

I remember "negotiating" that limitation with JasonLion as he and chem geek were developing the procedure for that test. It has been a stellar tool for us to use and all credit to those two for it's creation.

 

[Bperry]

I just tested CYA and I lost 10ppm(From 60 to 50) from 4 days ago when I tested right before performing the SLAM. Should I continue using the 60ppm of CYA till I am done with the slam or trust the 50 and use that to determine FC level?

The error tolerance on that test is +/- 10ppm on a good day. Don’t worry about it. Use the level is reads at.

 

[joshlarsen]

The error tolerance on that test is +/- 10ppm on a good day. Don’t worry about it. Use the level is reads at.

Sounds good and Thanks. Still learning

 

[joshlarsen]

Guys I'm back to having issues again. I SLAMed the second time from Aug 25 to Sep 2nd when my OCLT resulted in a .6ppm FC loss. I then proceeded and cleaned the filters on 8/4 and noticed some black crud at the top that I cleaned out and then for good measure raised FC up again and then performed another OCLT on 8/6 which I had no FC loss over a 4 hour window so claimed that as a pass. I then quit adding liquid chlorine and increased my CYA to 70 and over the course of 7 days backed the Salt Cell down in % till I got to 5.5 and then started increasing it again to try an target 5.5 to 6FC and the FC just kept going down. Even with my pump running 24 hours and my cell at 45% which I feel should be adequate for my 16k gallon pool. But as it kept dropping I decided to do another OCLT last night and over a 7 hour window lost 1ppm which yes I know is a pass according to the test criteria but something doesn't feel right. I then added 128oz of liquid chlorine and turned my cell up to 100% and tested a couple hours later and had a 7.4FC and then tested again 3.5hours later and still had an FC of 7.4.
Maybe I'm wrong but I feel like the cell running constant at 100% should have increased my FC from 7.4 atleast a little in 3.5 hours?

I really don't know where to go from here. My water is crystal clear and I have gone through absolutely everything with a fine tooth brush that I can get to. Even as far as

• Inspecting every nook and cranny of the pool and spa
• Removed weir doors
• Taking the valves apart to inspect inside
• Cleaning pump baskets
• Taking off intake/drain screens and brushing them and behind them
• Regularly flowing water through all pipes and heater
• Adding a schedule to run the bubbler pump for 30 minutes 3 days a week

I'll take the filter apart again tonight if the rain lets up or tomorrow to inspect that again. But well let it keep raining as long as we can since we haven't had any rain in 3 months in central TX.

I run my IntelliFlo VSF 24x7 at 1,100RPM which the pump says is pushing 28-29GPM

 

[Mdragger88]

After u pass an Overnight Chlorine Loss Test at target fc levels testing @ dusk (after the last addition) & dawn with swg off & have for certain ruled out algae,
U need to do an Overnight Chlorine Gain Test- basically the opposite of the oclt keep the cell on 100%, pump on all night, test at dusk & dawn to determine gain.
3 hrs isn’t really enough to guesstimate production - as the cell cycles on & off.
Here’s roughly what that cell should do in your pool in 8 hrs @100% when it was new.

Also - How old is your cell?

 

[Bperry]

Guys I'm back to having issues again. I SLAMed the second time from Aug 25 to Sep 2nd when my OCLT resulted in a .6ppm FC loss. I then proceeded and cleaned the filters on 8/4 and noticed some black crud at the top that I cleaned out and then for good measure raised FC up again and then performed another OCLT on 8/6 which I had no FC loss over a 4 hour window so claimed that as a pass. I then quit adding liquid chlorine and increased my CYA to 70 and over the course of 7 days backed the Salt Cell down in % till I got to 5.5 and then started increasing it again to try an target 5.5 to 6FC and the FC just kept going down. Even with my pump running 24 hours and my cell at 45% which I feel should be adequate for my 16k gallon pool. But as it kept dropping I decided to do another OCLT last night and over a 7 hour window lost 1ppm which yes I know is a pass according to the test criteria but something doesn't feel right. I then added 128oz of liquid chlorine and turned my cell up to 100% and tested a couple hours later and had a 7.4FC and then tested again 3.5hours later and still had an FC of 7.4.
Maybe I'm wrong but I feel like the cell running constant at 100% should have increased my FC from 7.4 atleast a little in 3.5 hours?

I really don't know where to go from here. My water is crystal clear and I have gone through absolutely everything with a fine tooth brush that I can get to. Even as far as

• Inspecting every nook and cranny of the pool and spa
• Removed weir doors
• Taking the valves apart to inspect inside
• Cleaning pump baskets
• Taking off intake/drain screens and brushing them and behind them
• Regularly flowing water through all pipes and heater
• Adding a schedule to run the bubbler pump for 30 minutes 3 days a week

I'll take the filter apart again tonight if the rain lets up or tomorrow to inspect that again. But well let it keep raining as long as we can since we haven't had any rain in 3 months in central TX.

I run my IntelliFlo VSF 24x7 at 1,100RPM which the pump says is pushing 28-29GPM

Only other advice would be to not adjust the salt cell quite so much at once. Keep it at 50% and get the water up to the right FC level with liquid. Then adjust the percentage up one notch and see how it does for a couple days but use liquid to keep it at the right level if it’s low. If the FC % is too high, just knock it down another % for another couple days and so on until you find the right balance.

And don’t bother measuring FC in 0.2 increments. Switch to 0.5 and you’ll have much less heartache.

 

[joshlarsen]

After u pass an Overnight Chlorine Loss Test at target fc levels testing @ dusk (after the last addition) & dawn with swg off & have for certain ruled out algae,
U need to do an Overnight Chlorine Gain Test- basically the opposite of the oclt keep the cell on 100%, pump on all night, test at dusk & dawn to determine gain.
3 hrs isn’t really enough to guesstimate production - as the cell cycles on & off.
Here’s roughly what that cell should do in your pool in 8 hrs @100% when it was new.
View attachment 447503
Also - How old is your cell?

My cell is basically new, we have had water in the pool since 4/28.
So for the OCGT. Basically if I loose lets say .5ppm of FC during an 8 hour long OCLT and I do an 8 hour long OCGT with my cell at 100% I should expect a net gain in FC of ~3ppm since my cell should generate ~3.5ppm in 8 hours at 100%. So if OCGT started at 10ppm I should expect it to end around 13. Is that correct? Is the OCGT basically just to prove the cell is working?

 

[Mdragger88]

That’s mostly correct (realizing that there can be error in the test of +-1ppm that is why 1 or less is passing)-
The effects of adding is an estimate but it should be close. Yes, The Ocgt is to check the cell but the possibility of algae must be ruled out. The next step after seeing bad results would be to have the cell tested.