Super Chlorination

[dvu]

Hello,

So I've read several post about super chlorination vs SLAMing. I believe I read one post from a senior member that stated as long as you maintain the right balance of chemicals that you don't need to shock (may have misread that). I'm still a little confused and maybe a lot of it is symantics. Anyway, here's my question. Isn't it inevitable to get combined chlorine, and when you do don't you need to shock it with chlorine or non chlorine based shock.

So here are my pool numbers:

30,000 gal pool with inline chlorinator using chlorine pucks.

Temp 86
pH - 7.4
Total Chlorine - 4.0
Free chlorine - 3.6
Total Alk - 120
Total Cal - 220
CYA- 50
Total DS - 400

So here are my questions:
1) Do you guys rec to super chlorinate when combined chlorine >0.4?
2) I tend to shock with lithium hypochlorite. I just don't want to mess with increased CYA or calcium. I know it cost more but would rather not mess with liq chlorine.
3) Lets say I shock to a level of 8 and resulting test show NO combined chlorine, when do you guys let kids back in the pool. I realize some of this answer will be based on chlorine/CYA and the belief that a higher cya needs a higher free chlorine and you really can't look at TC as a absolute number but need to take cya into account.
4) My pool installer rec leaving SI on the slightly corrosive side (-0.1 to -0.3). Thoughts. Do you guys shoot for balanced?

I'm sure I've got more questions but these are the ones off the top of my head. Any help is greatly appreciated. Thanks

 

[JoyfulNoise]

I suggest you go and read through our Pool School.

In a properly maintained pool, you almost never need to "shock" a pool. In the four years I've operated my pool, I have SLAM'ed the pool once and I have never needed to regularly "shock" it. Do I get CCs? Sure. They usually fluctuate anywhere from 0 to 0.4ppm and, on occasion, I have registered up near 1ppm. They all went away the following day with no rise in FC needed.

Shocking, "superchlorination", etc., is just all pool industry talk for selling you chemicals you don't need. If you follow the TFP methodology, "shocking" a pool is a thing of the past. Maintaining the correct FC/CYA ratio is the key to all of it. The only reason why pool stores and the industry tell you to "shock" a pool is because the chlorine levels they recommend are out of line with CYA levels and that usually leads to too little active chlorine levels (hypochlorous acid). When the active chlorine levels are maintained too low for too long, algae and pathogens can gain a foothold and start to proliferate.

Non-chlorine shock (potassium monopersulfate) is practically NEVER needed in a pool and, as far as oxidizers go, it is weaker than chlorine. It can help to increase the clearing rate of CCs, but again, in a properly maintained, outdoor residential pool chlorine is more than adequate to do the job.

For scaling, we use the calcite saturation index which is more accurate than the LSI because it takes into account the more detailed chemistry of calcium carbonate saturation and doesn't rely on "fudge factors" that are built into the LSI. A pool with a CSI maintained between -0.3 and +0.3 will have no scaling issues. If you have an SWG pool, it's best to maintain CSI between -0.3 and 0.

 

[Richard320]

You read correctly. Keep adequate FC at all times and you won't get algae so you won't need to shock.

1)In my pool, CC comes and goes. I use 10 ml test, so as long as 1 drop clears the CC, I ignore it. That means it's .5 or less.
2) You will have increasing CYA as long as you use an inline chlorinator with trichlor pucks. Spend as much as you want on lithium shock, but the CYA is still going to build on a daily basis.
3) It is safe to swim up to shock level for your CYA. In your case, that means up to 20 FC right now.
4) I have exceptionally high CH so I keep the CSI close to zero, with a preference towards negative, to reduce the risk of scaling. Keep it between -.3 and +.3 and you'll be fine. If your pool is vinyl-lined -- and you haven't filled out your signature so we don't know -- you can get as negative as you want because there is no plaster to etch. Just keep the pH in range for swimmer comfort.

 

[dvu]

Great. Thanks for the help.

 

[dvu]

One more question on checking cya. I use the Taylor test kit. The instructions says after mixing the solution essentially drop it in until the dot just disappears. So for y'all does that mean the point where it just starts to fade or when you can't see the black dot at all?

Thanks

 

[pabeader]

When you can't see it any more. Since the scale isn't linear, we like to suggest that you fill to a line, let's say 90. Then glance at the dot. Don't see it? Add up to the next line. Glance. Repeat until you are successful in not seeing the dot. Do not stare or your mind may play tricks on you.

 

[dvu]

Thanks. Your approach makes a lot of sense.