First SLAM - When to start

[rldaniel]

Over the past couple of weeks, I noticed that my FC level has been slowly dropping, although it never got below 4. Previously, with the settings on the pump run time and SWG% it was holding around 7 to 8 when I would test it around 3:00pm every day. My CYA had gotten down to 60 at one point, so I convinced myself that the FC drop was caused by my CYA being a little low and I added enough a few days ago to get it back to 80. It has also been very clear with high UV index for the last week and figured that was also contributing to the low FC.

Test from yesterday morning
FC - 6.5
PH - 7.8
TA - 70
CH - 250
CYA - 80
Temp - 80

The pool is still crystal clear, but yesterday morning I noticed some algae on the sloped wall in the deep end. It easily brushes off with a cloud of brown green behind the brush. My problem is two fold. My daughter just dropped off the grandkids to spend time with us while she goes to the beach with her old college girlfriends for the next 5 days, and of course the kids want to swim. Secondly, my CYA is now at 80, and is it practical to SLAM like that?

I can't decide whether to raise the FC, say to 10 or 15, to keep the algae at bay while the grandkids are here and then do the SLAM when they leave, or just start the SLAM now and raise the FC to 31. I know you can swim up to SLAM levels, but 31 seem a little much for small kids. Maybe I am being paranoid, but I am looking for advice. Also, should I even try to SLAM with a CYA of 80, or drain some water first. I'm thinking to try it with a CYA of 80, as I suspect this will be a relatively short slam as the water is still sparkly clear.


Thanks,

Ron

 

[bmoreswim]

To address your concern of having the grandkids there while you would ideally be performing a SLAM, I would personally follow your approach more or less. Raise the FC level halfway to SLAM, run the pump 24/7, brush once or twice daily, and raise FC higher than that after the last swim of the day. Then proceed to SLAM after the visit it over.

One other item to consider is whether your SWG is failing. They fail slowly, often first by reading lower salinity than is actually in the pool per the K-1766. And during that time, they will produce less chlorine. It’s usually not a working then not working situation. Otherwise, it is likely just that FC got to or below minimum and algae got a foothold and SLAM will resolve all after your visitors leave.

 

[rldaniel]

I was checking FC in the middle of the afternoon and the lowest reading was 4.5 then. I had the pump to cut off at 4:00pm and back on at midnight. I wonder if the FC was dropping below 4 during the afternoon and into the evening allowing the algae to get a foothold. I was also running a sprinkler to help cool the water, and that is why I I had it shut off at 4:00pm, so we could use the pool without it running. Maybe I need to rethink how I run the pump.

The SWG is only a couple of months old, and seems to produce lots of small bubbles that can be seen in the clear Circupool housing. I cranked it to 100% last night and it had the pool at 10ppm this morning. I think it is working correctly.

 

[kellyfair]

If you were at 4.5 FC with CYA at 80, and then turned off pump and SWG for several hours, there’s your answer. There’s nothing wrong with turning it off for a few hours, but you want your FC high enough when you do that so that you don‘t spend several hours below proper FC level. Adding swimmer load as well just means your FC goes even lower. Also, you don’t want to rely on SWG to boost FC, just to maintain it.

Once you’ve SLAMmed and everything is golden, i would keep CYA at 70 or 80, and boost FC with LC to a couple of points above target. Then, if you have a big load of swimmers, consider adding some LC after, and turn pump and SWG back on.

 

[rldaniel]

Just to add a wrinkle to this story, my wife has traditionally taken care of the pool, taking samples to the pool store every week and putting in what they say. She usually had algae once or twice a summer and would use algicide and whatever the pool store recommended. She use di-Chlor pucks and I just let her do her thing. Looking back, we had a significant leak and were regularly adding water, so I bet the CYA never got sky high and made the use of the pucks sustainable. The leak is fixed now and I told her I would take over the pool to give her a break. Thats when I stumbled onto this site and switched over the the TFP methodology, so I have little experience with pools care and just added the SWG a couple of months ago, so I also have little experience with SWGs.

I say all this because I did a OCLT last night and it stayed at 11.5 all night. I was surprised it passed. Like I said, I don't really know what algae looks like, but my wife said it was algae and it definitely had a brown green trail of dust behind the brush when I passed over it. I took out the light and cleaned out the cavity although it didn't have much debris. I also took some pure 10% chlorine and scrubbed out the basket as it had some brown green stains. I also scrubbed the ladder and found just a little something under one of the rungs near the stainless steel outer support. I could have been rust as the support is stained brown where I cleaned. Could just raising the FC level to 11 with the SWG for two days have killed it all? The pool is still sparkly clear. I will keep the pool FC at 11 or 12 for the rest of the day and do another OCLT tonight just to make sure. Like I said, I am new to this so any advice would be appreciated.

 

[kellyfair]

It’s up to you, but the fact that it was growing on the wall indicates that it is algae. If your CYA is 80, you haven’t come close to SLAM level. Did you keep your SWG on all night?

You can follow your plan, but be on the lookout for a repeat. Personally, I would get up to SLAM level for at least a couple of days, to insure that I got it all.

 

[rldaniel]

Kelly, sounds like good advice. No, I had the SWG off during the test last night. When the kids leave I will boost it up for a few day and see if I can still pass the OCLT afterwards. Thanks for the help.