SLAM question.


Gold Supporter
In The Industry
Apr 22, 2019
Homer, AK
Here are my numbers: FC - 1-1.5 ppm; PH - 7.5-7.6; ALK - 60; CH 200; CYA - 0; Salt -0.

This is an indoor therapy pool kept at 95 degrees, 8 hours a day. I know, the TFP people think I should have 20+ CYA, but I just want to agree to disagree about this. My question is how often do you think I should shock the pool? I shock the pool on weekends when nobody is in it. I do it with 1-1.5 gallons of Clorox bleach. No windows in this pool room. I have a Stenner that keeps it at 1-1.5 ppm FC during the week. MA easily controls the PH. The real reason I want to shock is to destroy the bacteria in the pool so I can keep the FC at a low level all week. Algae is not an issue (people here have water delivered into 1500-2000 gallon tanks and it never is a problem). OK, so here's the question: should I be shocking every week? Every 2 weeks? Sometimes the therapists are in the pool for 7 hours a day. Any thoughts?


Bronze Supporter
Mar 5, 2020
Melbourne, Australia
Pool Size
Salt Water Generator
SWG Type
Astral VX 7T
My opinion on this is: If you have bacteria that survive in your pool until the weekend, then you have a problem. I would not consider that pool safe to swim in.

Edit: Just added a "not" to the last sentence.
Last edited:


Gold Supporter
LifeTime Supporter
TFP Guide
Oct 25, 2015
Pool Size
Salt Water Generator
SWG Type
CircuPool RJ-30 Plus

Here's my $.02. Shocking at a time interval doesn't make sense to me. As you probably know we don't advocate shocking anyway we use a SLAM which is a process not a one time event. If you want to be sure you have no harmful bacteria you must maintain an FC level at the levels described in our FC/CYA chart. With people in the pool as long as often as you have your biggest risk is very low FC levels not missing a "shock" event. If it were me I'd test FC at least at open and close each day with a FAS-DPD test kit and keep the FC level to TFP minimum based on the chart. I think the stenner pump helps to ensure you don't drop below minimum but any change in load or contamination could make the pool unsafe for the rest of your clients until you adjust the pump. You certainly need to test above minimum to ensure the entire pool is safe all day. Remember mixing is not perfect in any pool so if you test at minimum somewhere you're likely below that somewhere else. As far as when to SLAM keep an eye on your FC and CC. Even though you don't have algae you do have a lot of traffic. Lotions, body discharges, and other contamination can consume your FC level to a dangerous level very quickly especially when you're running on the ragged edge of minimum safe FC all the time and that would be the time to close the pool until you complete a SLAM to be sure the pool is safe for you and your clients. Just because nobody's gotten sick yet doesn't mean they won't. It's actually difficult to transmit disease in most cases if you have close to min FC but this is a low probability risk with very high consequences so I wouldn't use your pool.

I hope this helps.

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