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Basic Dichlor / Bleach Cheat Sheet


RedCourt

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After reading a bunch on this forum I think I've (mostly) got me head around maintaining our new Hot Tub. I made myself an excel log for my readings and a single page "cheat sheet" for me to keep with my Taylor kit to reference. If someone (Chem Geek?) would take a gander and let me know if there is something I'm missing / forgetting or not addressing I'd be very appreciative. :-)

Initial setup with new fill

· Balancing water after a new fill:

o Bring temp up to 100 degrees

o Run all jets and air features

o Add 50 ppm Boric Acid (15oz for 380gal tub) and adjust Calcium Hardness CH to 140 (should not have to do often unless water volume is changing. As long as it’s over 100 you can choose not to increase it, but other numbers here will be different. Use The Pool Calculator to check those numbers.)

o Continue to run all jets and air features (this impacts pH)

o Adjust pH to 7.5 (7.5 is pH of human eye)

o Lower Total Alkalinity TA to the point where Calcite Saturation Index CSI is zero (should be 110 before introduction of CYA from Dichlor, may need to be 115+ after.)

· Shock and determine baseline Chlorine Demand:

1. Shock tub to approx 10 ppm FC using Dichlor the first night after filling. (Note number and do not use tub!)

2. Wait 24 hours and test FC again in order to calculate Chlorine Demand. (ok to use tub after this step)

3. CD = Measurement from #2/#1

Ongoing Maintenance

· Check FC before soaks and add dichlor / bleach after soaks.

· Use Dichlor after soaks ONLY until you have added enough to raise CYA to 20ppm (2oz for 380 gal tub) then switch to Clorox unscented bleach 6% after that.

· Add MPS before/during high bather loads to help out the Chlorine, and keep CD low. (Good to also use MPS instead of bleach sometimes after soaks)

o Guideline per person per hour is:

§ 3-1/2 teaspoons of Dichlor or

§ 5 fluid ounces of 6% bleach (e.g. Clorox regular unscented) or

§ 7 teaspoons of MPS non-chlorine shock

· Check pH once a week, and adjust TA as needed.

· Rinse filter(s) every week or two, depending on use.

· Check CYA every 3 months, and raise by using Dichor if needed. CYA will drop slowly over time.

· Use Sea Klear (clarifier) if you experience foam, or cloudy water.

Water Change

· After 3-6 months, change water and start over.

o Shop vac out dregs and flush with fresh water, wipe down inside and clean w/ enzyme if necessary

· Consider using a Spa Flush to clean out pipes before draining 1-2 times a year.

· Clean filter every water change. (See separate cheat doc)

· If the FC drops to zero for any length of time or you're having serious medical issues (i.e. rashes etc.) consider doing a full decontamination.

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I'd lower the TA before you add the boric acid (borates) because it will be easier to move the pH during the acid addition and aeration process.

Do not worry about the CSI unless you have a plaster spa. If it's the normal acrylic or fiberglass, do not worry about the CSI (unless it's high, but that's doubtful since you'll be lowering the TA and only adding CH to prevent foaming). And for sure you don't adjust the TA for the CSI -- you lower the TA to around 50 ppm for pH stability if you are going to use a hypochlorite source of chlorine such as bleach.

Use Dichlor until you get to 30 ppm. The 20 ppm was older and it seems better to get to 30-40 ppm that has the chlorine outgas less and has the chlorine be somewhat less harsh. It's still much better than when the CYA gets very high if you were to use Dichlor-only.

As for using MPS sometimes instead of bleach, I'm not so sure that's necessary. Most people don't.

As for the time between water changes, that depends a lot on your bather load. The standard Water Replacement Interval (WRI) adjusted for Dichlor-then-bleach and using person-hours is Days = (2/9) x (Spa Size in Gallons) / (Person-Hours Per Day) and many people go longer than this, but as a guideline you should be able to go at least this long.

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Thanks Chem Geek, I appreciate your replies and the level of knowledge you bring to these conversations. I'm not using Nature 2 (asked on different post) but I'm wanting to look into it as an option for the future. I revised my cheat sheet based on your feedback, and thank you! I was absolutely using the CSI to determine my TA. I was figuring my ultimate goal should be a CSI as close to 0 as I could possibly get it. I left the MPS in the cheat sheet, mainly because I already bought it, but if there is no benefit to it I'll just use it up and stick to bleach. I also calculated my estimated WRI based on your formula and it seems to make sense, but I came across another post you made where it seemed like you were using the weekly bather load in this formula instead of the daily. I hope I'm doing it correctly, because I'd hate to use the tub for 7 times the suggested replacement interval!

Initial setup with new fill

· Balancing water after a new fill:

o Bring temp up to 100 degrees

o Run all jets and air features

o Lower Total Alkalinity TA to ~50 ppm (for pH stability)

o Add 50 ppm Boric Acid (15oz for 380gal tub) and adjust Calcium Hardness CH to 140 (to prevent foaming. Should not have to do often unless water volume is changing. As long as it’s over 100 you can choose not to increase it, but other numbers here will be different. Adjust accordingly)

o Continue to run all jets and air features (this impacts pH)

o Adjust pH to 7.5 (7.5 is pH of human eye)

· Shock and determine baseline Chlorine Demand (CD):

1. Shock tub to approx 10 ppm FC using Dichlor the first night after filling. (Note number and do not use tub!)

2. Wait 24 hours and test FC again in order to calculate Chlorine Demand. (ok to use tub after this step)

3. CD = Measurement from #2/#1

Ongoing Maintenance

· Check FC before soaks and add dichlor / bleach after soaks.

· Use Dichlor after soaks ONLY until you have added enough to raise CYA to 30ppm (~3oz for 380 gal tub) then switch to Clorox unscented bleach 6% after that.

· Optional: Add MPS before/during high bather loads to help out the Chlorine, and keep CD low. (Can also use MPS instead of bleach sometimes after soaks, but it costs more w/ no significant benefit.)

o Sanitization guideline per person per hour is:

§ 3-1/2 teaspoons of Dichlor or

§ 5 fluid ounces of 6% bleach (e.g. Clorox regular unscented) or

§ 7 teaspoons of MPS non-chlorine shock

· Check pH once a week, and adjust TA as needed.

· Rinse filter(s) every week or two, depending on use.

· Check CYA every 3 months, and raise by using Dichor if needed. CYA will drop slowly over time.

· Use Sea Klear (clarifier) if you experience foam, or cloudy water.

Water Change

· After 3-6 months, change water and start over.

o Water Replacement Interval (WRI) adjusted for Dichlor-then-bleach and using person-hours is Days = (2/9) x (Spa Size in Gallons) / (Person-Hours Per Day) so for 2 people using the spa together

§ 2 people x15 min/day: (0.2 x 380) / (0.5) = 169 days (~5½ months)

§ 2 people x 30 min/day: (0.2 x 380) / (1) = 84 days (~2⅘ months)

· Shop vac out dregs and flush with fresh water, wipe down inside and clean w/ enzyme if necessary

· Consider using a Spa Flush to clean out pipes before draining 1-2 times a year.

· Clean filter every water change. (See separate cheat doc)

· If the FC drops to zero for any length of time or you're having serious medical issues (i.e. rashes etc.) consider doing a full decontamination.

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The WRI is based on person-hours per day, not per week. Your writeup is fine for the WRI. However, many people have found that they can go even longer than the WRI that I already doubled from the standard WRI when using Dichlor-then-bleach. It may be that they rinse off before soaking.

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