SWG and SLAM

Holydoc

Gold Supporter
Jul 17, 2016
418
Navarre/FL
Just a hypothetical here...

During a SLAM, it is typically recommended that you turn off your SWG. If you are a follower of TFP, you most probably purchased an SWG that is twice the size necessary for your pool. Given that if you had to perform a SLAM wouldn't it be beneficial to bring your water up to SLAM level with liquid chlorine and then set your SWG on 100%, running your pump 24/7, to maintain that SLAM level? I mean this, in theory, should save you from adding that much more liquid chlorine since your SWG would be supplementing most of the loss due to chlorine loss from the algae. Of course when you perform an OCLT you would need to turn your SWG off to determine if you had any chlorine loss over the night.

Am I missing something or does the above sound logical?
 

splashpad

Bronze Supporter
Aug 2, 2017
2,708
SE Kansas!
The reason for turning it off, is so you can accurately monitor FC drops :)

In addition, the SWG cells HAVE a lifespan, no reason to shorten the life span when the FC levels must be raised & maintained much higher then most SWG cells will even go (based on CYA).
 

Holydoc

Gold Supporter
Jul 17, 2016
418
Navarre/FL
Splashpad,

Are we actually monitoring FC drops during a SLAM or monitoring that the FC is at SLAM level? I know for the OCLT we are measuring FC drops. But during the SLAM, we just want to keep a certain FC level.

I totally understand the lifespan reasoning for the SWG. I wonder how much lifespan we are actually using if we just did that 100% SWG for the short time it normally takes a short SLAM. I am defining a "short SLAM" as one of those where you see a bit of algae on your steps or pool floor and SLAM it to PREVENT an Algae bloom. If your pool is in a full green algae bloom, then I would not suggest this technique of using the SWG since it may have to be utilized for a prolong amount of time.
 

splashpad

Bronze Supporter
Aug 2, 2017
2,708
SE Kansas!
Are we actually monitoring FC drops during a SLAM or monitoring that the FC is at SLAM level? I know for the OCLT we are measuring FC drops. But during the SLAM, we just want to keep a certain FC level.
That is the same thing ;)
Testing the FC often so that when the chlorine gets used up (aka drops/falls/lowers), then FC is added. The (average?) SWG just wouldn't produce enough FC at the rate needed, especially since the SWG are operated with generally higher CYA levels.
 

Holydoc

Gold Supporter
Jul 17, 2016
418
Navarre/FL
Hmm... may be an experiment worth trying since liquid chlorine is scarce for many people right now. Problem is that I do not need to SLAM so test would be a bit skewed towards the SWG being able to keep up the chlorine requirements. After all, you would have a larger demand for chlorine if algae is present since it would work in conjunction with the UV light to break down the chlorine. But if using your SWG would reduce the liquid chlorine demand in half or more, then it may be worth using during a SLAM for those that cannot readily purchase chlorine now.

Let me lower my pH to 7.2 and raise my FC to SLAM level (28ppm for my pool) and see how well my SWG can maintain this FC level during a hot (85deg) sunny day in Florida. My pool is in 100% sunlight all day so this should tell me how high I need to turn my SWG to overcome the UV light. That should reduce my intake of liquid bleach by quite a bit during a real SLAM, I would assume.
 

Windylou

Silver Supporter
May 11, 2017
231
Groveton, Tx
I read somewhere that you could use it to help maintain, but that it couldn’t produce enough for that level fast enough. I did use mine last year during a SLAM, I put it on super chlorinate. I waited until SLAM had finished this year before I turned it on. I wouldn’t want to shorten it’s lifespan just to SLAM though.
 

Holydoc

Gold Supporter
Jul 17, 2016
418
Navarre/FL
Windylou,

That is exactly what I am doing. I am using it to maintain by placing it on Super Chlorinate. Even just using it to maintain, I still am required to add some chlorine (see my log files) though the additional chlorine has been reduced by using the SWG. Where some people have Murphy move in, I had Murphy move in the form of an approaching tropical storm. :)

Yesterday, I was battling UV from the sun. Today I am battling rain from the upcoming Tropical Storm.

Once I got my pool up to SLAM level, I was able to maintain with 2 - 3 quarts of liquid chlorine every 4 hours or so. Of course the dilution of the chlorine by all the rain, makes this test not as conclusive as I wanted. What the heck, it is fun anyway seeing what is possible.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,321
Laughlin, NV
I see no issue using the SWCG to maintain your SLAM level FC, or at least a supplement maintaining it. The big deal is, to keep testing. At least 3-4 times per day. And add liquid chlorine as needed to get back to SLAM level FC.
 

Windylou

Silver Supporter
May 11, 2017
231
Groveton, Tx
Windylou,

That is exactly what I am doing. I am using it to maintain by placing it on Super Chlorinate. Even just using it to maintain, I still am required to add some chlorine (see my log files) though the additional chlorine has been reduced by using the SWG. Where some people have Murphy move in, I had Murphy move in the form of an approaching tropical storm. :)

Yesterday, I was battling UV from the sun. Today I am battling rain from the upcoming Tropical Storm.

Once I got my pool up to SLAM level, I was able to maintain with 2 - 3 quarts of liquid chlorine every 4 hours or so. Of course the dilution of the chlorine by all the rain, makes this test not as conclusive as I wanted. What the heck, it is fun anyway seeing what is possible.
I see you’re in Navarre, I’ve passed through many times. My daughter lives in Santa Rosa Beach. You guys are getting a ton of rain right now. That certainly doesn’t help things! It’s good to know the SWG can help maintain, especially with chlorine being harder to find right now.
 

Holydoc

Gold Supporter
Jul 17, 2016
418
Navarre/FL
Yes I love the area with the beautiful, crystal white beaches. Yeah the rain is not helping the test but this experiment did answer one question. The SWG, that is rated twice the size needed for the pool, can help maintain a SLAM, but cannot do it on its own. You still have to continue to add liquid chlorine to maintain even running at Super Chlorinate.
 

Newdude

Well-known member
Jun 16, 2019
4,568
NY
The whole ‘shortening the lifespan’ thing is technically true but very misleading. If one normally runs 12 hours a day and needs to slam for 24 hours for a week, They only used 84 more hours, or roughly 1% of an 8k+ expected lifespan. With the average unit probably around $600, It costs $6 extra for the week. Yes it will die earlier. A whole week earlier after a couple years of use. You will never even know. The chlorine it produces will be more than the $6 if you used only liquid so it’s cheaper that way also.

the first part of the battle will need some help with liquid. The rest (75%?)..... the ‘M’ for maintain.... is what the SWG was designed for. And it’s also where people get lazy/busy and slack, furthering the slam by a few days or even more.

until you can pass the clarity test for the SLAM, you are not ready for the OCLT anyway. When that time comes, shut off the SWG at night.

*disclaimer. Some people want the SWG to last as long as possible regardless of cost or inconvience. If ‘prolonging the lifespan’ helps you sleep at night than by all means, You do you.