My first attempt at a TFP Fill - Questions to Ace the Test


New member
Apr 16, 2018
Victoria, BC, Canada
Hello! I’ve been quietly browsing this forum every since I bought and installed my swim spa (see my sig for details). Thanks for all the free advice you’ve all provided me so far!

I’ve purchased the TF-100 kit and I’m about to do a drain-clean-refill. Chemicals that went into the current (first) fill was based on the spas vendor’s advice (basically a lot of products and very little chemistry lesson). My most recent TF-100 kit test tells me the water I’m about to dump is at:

pH 8.2
TA 110
CH 175
CYA 40

My family hasn’t complained about the water quality - but I’d feel better about getting a stronger grip on what’s going on so I’m currently planning to follow Nitro’s stickied post so essentially these goals:

CH 150 (130-150)
pH 7.5 (7.2-8.0)
TA 50 ppm
CYA 30 ppm (20-30)
FC 5 ppm
Then ~50 ppm Borate

Sorry in advance for the questions! I thought I had it all figured out but then self-doubt creeps in - and I hope to get it right this time around:

  1. It was a new spa when I bought it last year. Should I need to do a flush out with hot tub flush product? What about after it’s drained, I’ve read “hot tub cleaner” and a soft cloth? If so, what hot tub cleaner product should I look for to wipe it down?
  2. My filters are Coast Spa 175 SqFt Dual Core PRDC550-AFS Pleatco. I have two of these that I’m told to rotate so one is soaking in fresh water while the other is in use. Every week I’m supposed hose clean and swap them, storing the spare in a water bath. I’ve received contradictory advice on chemical cleaning: (a) Every month use an entire pack of filter cleaner powder (about an 8 tablespoon package) to 12-hour soak the filters OR (b) Put spare filter in container with water and ¼ teaspoon of the powder cleaner each week. Both these methods seem excessively frequent to me. I’m not seeing much out of the filters when I hose them down. Is there a better plan?
  3. When I use my pool vacuum to get bits of debris that has fallen in I noticed I also pick up little flat white flakes that are brittle when touched when dry. People don’t notice them when in the water - it’s only evident when I vacuum some up. Is this expected to go away as I improve my water management this time around? Or could this be construction debris from being the first fill of a new swim spa?
  4. I was sold a lot of chemicals on my first purchase. Rather than just tossing them I figure I should try to identify what they really are to see what can be used still in the TFP plan before I go out a buy less expensive alternatives. Here’s my best guess, and some I couldn’t figure out at all. Any advice and/or correction would be appreciated:
    1. Spa Essentials Sanitizer, “Sodium Dichloro-s-triazinetrione Dihydrate”, best guess: Dichlor, can be used for TFP plan.
    2. Aquarius Pool Water Stabilizer, no chemicals listed, “conditions water to maximize the protection of stabilized chlorine”, “acts as a shield to reduce the destructive effects of direct sunlight on the chlorine residual”, “the ideal range is 30-50ppm”, best guess: also Dichlor, can be used for TFP plan.
    3. Spa Essentials Quick Clear, “potassium peroxymonosulfate”, best guess: MPS, can be used for TFP plan, if/when required.
    4. Spa Essentials Super Soft, “boric acid and zinc sulfate”, best guess: Boric Acid (AKA equal to what Nitro mentions as “Gentle Spa” in his post), can be used for TFP plan.
    5. Natural Chemistry Spa pH Up, “Sodium Carbonate”, best guess: Soda Ash, probably not needed for TFP plan as it raises TA too, but I’ll keep it.
    6. Natural Chemistry Spa Alkalinity Increaser, “Sodium Hydrogen Carbonate”, best guess: Baking Soda, can be used for TFP plan.
    7. Natural Chemistry Spa Calcium Hardness Increaser, “Calcium Chloride”, best guess: Calcium Chloride, can be used for TFP plan.
    8. Guardex pH Decreaser, “Sodium Bisulfate”, best guess: Dry Acid, can be used for TFP plan.
    9. Spa Essentials Balancer Stain and Scale Control I, “Contains Phosphoric acid”, best guess: No idea!! I was originally told when starting with fresh water to add 3 bottles (500mL each) to 85 F or hotter water. Which I did, but I don’t plan to this time unless you TFP folks tell me it’s a good idea.
    10. Spa Essentials Balancer Stain and Scale Control II, “Contains Etidronic acid and Phosphonic acid” (not a typo, it’s different than the Phosphoric acid in the prior bottle), best guess: No idea!! I was originally told to add 3 caps weekly, but I haven’t. I don’t have any stains or scales that I can see. Probably just going to set this aside unless TFP advises differently.
    11. Coast Spas Clear 4-in-1 Clarifier for Spas and Hot Tubs -”The active ingredient is a natural polymer from crustacean shells” Best guess: No idea!! I was originally told to add Use 4 squirts of coast clear weekly. I’ve not bothered. TFP advice welcome on this! =)

I embraced the "making your questions as detailed as possible" mantra. Hope it's not too much!


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New member
Apr 16, 2018
Victoria, BC, Canada
Oh I missed a question!

Question #5:

Quoting Chem geek from here: Do I really need to drain and re-fill my hot tub?

With the Dichlor-then-bleach (or pure CYA then bleach) method, you get roughly twice the amount of time between water changes compared to Dichlor-only. The rough rule-of-thumb for the Water Replacement Interval (WRI) with Dichlor-then bleach and having no ozonator is the following:

WRI = (2/9) x (Size of Spa in Gallons) / (# of person-hours per day)

You don't have to change the water at the WRI -- it's just a rough guide.
I tried that formula out in my case and I get:
WRI = (2/9) x 1405 gallons / 0.43 person-hours per day = 726 days = ~2 years.

Now I know it's only a rough guide subject to many many other factors, but if it's in the right ballpark I figure I might be able to just do one water change once-a-year in spring. Or have I stretched the formula out of it's intended bounds?


Mod Squad
LifeTime Supporter
Platinum Supporter
TFP Expert
Aug 10, 2012
Welcome to TFP!

These will answer most of your questions. I've been using this method to maintain my hot tub for quite a few years and it works great.

How do I use Chlorine in my Spa (or pool)?
Pool School - Maintenance and Cleaning of Pool Filters
Pool School - Recommended Pool Chemicals

We do recommend using ahhh-some to flush spas, even new ones. The flakes are likely calcium scale from overly high pH contributed to by overly high TA. I only change my water once or twice a year and we use it a LOT.


New member
Apr 16, 2018
Victoria, BC, Canada
Thanks for the response. It all seemed too easy so I was worried it was abbreviated! I guess I won't worry about special 12-hour filter cleaner powder soaking from now on if a garden hose is all it takes.

I'll buy some ahhh-some for my water change.

Also good to know I'm not insane with the idea of changing the swim spa water annually if it continues to be underutilized.