Fresh Fill - Timing And Sequence Of Chemicals

[Oaxacaquarius]

I have just drained and refilled my 170 gallon outdoor spa and am waiting for the temperature to rise to 104 degrees (where I like it). It's currently at 60 degrees and rising as it should. My question is when, and in which order, I should begin adding the following chemicals. (I am following ChemGeek's method and using the Pool Calculator. Also I used a Taylor kit to check my current measures.)

FC = 0 (want to add dichlor to 10 ppm (eventually adding enough dichlor over the week to get me to a CYA of 20, thus approximately 22 ppm of dichlor, then all regular 6% Clorox bleach from there.

pH = 7.6 (out of the tap; it's nice and easy). I want to keep it there.

TA = 70 (I want 80, so I'll .4 oz --by weight -- of baking soda.

CH = 100 (I want to raise it to 160, so I'll add 2.3 oz -- by volume -- of calcium chloride dihydrate.

Borate is, I assume 0 -- I have no way of measuring for sure -- but it is a fresh fill. I am adding Gentle Spa per directions on bottle to get to 50 ppm (and leaving it at that until the next drain and refill.

According to PoolMath's calculatior, this should give me balanced spa water at 104 degrees in my 170 gallon spa.

If any of this sounds off, please let me know. But I am wondering if I should start adding the sanitizer (dichlor) at some point before my water temperature reaches 104 (tomorrow night, probably) since my FC = 0 and bacteria multiply quickly -- especially in warmer water.

Also, does the sequence in which I add these various chemicals matter? I assume I should try to balance the TA first with the baking soda, then add the dichlor to raise the FC (initial shock at 10) , then the calcium chloride dihydrate, and finally the Gentle Spa (with Borates). Does this sound right? And if so, at what temperatures -- ideally -- would I add each?

I am new to all of this. I apologize if this sounds like an ignorant raft of questions.

[Oaxacaquarius]

Does anyone have any advice to offer? i am at 95 degrees now.

[chem geek]

You don't want the chlorine level to get to 0, certainly not for very long (more than just an hour or two). The temperature for adding the chemicals doesn't matter. People have reported Gentle Spa raises the pH. Using boric acid from Duda Diesel or The Chemistry Store. You do NOT want 80 ppm for TA -- it should be lower at around 50 ppm instead and you should not add the borates until you get the TA lower (via acid addition with water aeration).

[Oaxacaquarius]

Thanks for replying Chem Geek. I am curious -- why a TA of 50 ppm?

[Oaxacaquarius]

I found an old post of yours from April 27 2010 in a thread started by Nitro on "Lowering Total Alkalinity." You write, "Odds are, after switching to bleach after a week or so of Dichlor that you will need a low TA of perhaps 50-60 ppm. If you still find the rate of pH rise too high, you can also use 50 ppm Borates."

Thank you!

[Oaxacaquarius]

I still have one question about Gentle Spa. Nitro (in his "Guide to Water Maintenance" post) writes:

"Lastly, there is one more thing I haven't mentioned that you can add to your tub that will help buffer your pH, Borates. The easiest way to add Borates to your tub is to get a product called Gentle Spa. It is pH balanced, so there is no need to add acid to counter balance it. The ideal amount is ~50 ppm, and only needs to be added once per water change. That will help keep your pH from drifting from aeration. Not to mention, actually make your water feel silkier. I highly recommend it."

If it is pH balanced, why do you suppose people have reported that it raises pH? (I bought, but have not yet added, Gentle Spa after reading Nitro's recommendation, but before reading your response above. Now I am feeling reluctant to add it. You are recommending boric acid -- would Mule Team 20 work? Or is the quality of this source to impure?

[Oaxacaquarius]

I just re-tested the water with a Taylor kit after reaching my target temperature of 104 degrees.

TA= 80

pH= 7.6

CH = 110

FC = 17 (still, after shocking last night). When it drops to FC =3, I was hoping to get in the tub.

I am aerating now and waiting. I have not added any Borates or Boric Acid (nor Gentle Spa).

I am reticent to reduce my TA at this point because everything seems close to balanced. I am considering adding 0.5 ounces of calcium chloride.

Also - I followed the Pool Calculator and added 0.4 oz (by weight) of dichlor to raise my FC from 0 to 10, But I am at 17. How is this possible? And is it a problem, or should I just wait and let it slowly drop? Does this mean that I have added 17 ppm of dichlor? I want to keep my CYA at 20, so I am trying to keep an accurate count of how much dichlor I am adding before switching to bleach.)

Any advice for me at this stage?

[chem geek]

Since you've already got the Gentle Spa, you can use it. Just note that you may need to add acid to balance the pH. It seems that they changed the composition of it so that it isn't as pH balanced as it used to be.

The lower TA reduces the rate of pH rise from carbon dioxide outgassing.

The 17 ppm FC will come down. I don't know why it didn't measure correctly.

[Oaxacaquarius]

Thank you Chem Geek! The FC did come down -- to 6 ppm. I have the CH at 140 ppm now. The pH is 7.8 (ish) judging from the Taylor Kit, and turns to 7.6 with one drop of the acid demand test solution. My TA is at 70 ppm. For my 175 gallon tub, I have calculated that I need to add 0.21 oz. of Sodium Bisulfate (93.2%) to hit my target of 7.6. But I know that you say I should be targeting a lower TA (between 50-60 ppm), rather than thinking about hitting my pH target, which I can always raise later if necessary by aerating. I will add the dry acid until I get my TA in range (between 50-60 ppm) and pH to 7.6, and then add the Gentle Spa (4 ounces).

If you were me, how much dry acid would you add at this point?

0.21 ounces is less than one Tbs, so I assume that I can add it all at once while aerating. But perhaps you would suggest that I try to shoot lower than my ultimate target (add more dry acid than this amount), in anticipation of a rise in pH? For example, if I shoot for a pH of 7.2 now (by adding .4 ounces (by weight) of dry acid, and trust that aerating will bring it up to 7.6 in good time -- am I more likely to hit my target TA of 50-60 ppm, or would I risk reducing my TA too much and "disturb the balance in the Force."

I simply do not yet have a sense of the ebb and flow of this process, nor how the dynamic changes when I cross beyond certain critical TA boundaries.

[chem geek]

I would add about 3/4 ounce of dry acid which will get your TA down to around 50 ppm. While the pH could go as low as 6.7, it likely won't get that low and the Gentle Spa you add next will likely raise the pH.

[klhPerry]

chem geek! We have a 240 gal bromine hot tub that I maintain using guidelines I found on this forum from Waterbear, Nitro, and you! I need your opinion on brominating tabs...I was using ProTeam tabs (bromochloro-5, 5-dimethylhydantoin 98%) and things were good. While I was out of state caring for my parents, my hubby took over the maintenance, consulting a hot tub retailer for advice. Ended up with Leslie's Bromine tabs (1-bromo 3-chloro5, 5-dimethylhydantoin 54.2%, 1,3-dichloro-5, 5-dimethylhydantoin 28%, 1,3-dichloro-5ethyl-5-methylhydantoin 15.9%...whew!)

When I returned home, the bromine levels were sky high. I aerated to lower as much as possible, and put the ProTeam tabs back in the floater. Do you feel that the ProTeam tabs are best when compared to the Leslie's? I'm no chemist, but the list of ingredients on the latter seems crazy! Thank you in advance for your input.

[chem geek]

I'm guessing that the Leslie's bromine tabs dissolved faster due to the DCDMH in them (they also have BCDMH) whereas your ProTeam tabs are only DBDMH. The chlorine reacted with the bromide in your water to make more bromine. The Leslie's tabs are usable if you turn down your feeder (assuming you can turn it down low enough) and if you make sure you have a bromide bank which if you've been using bromine tabs for a while you should. If you have a fresh fill, then you'd need to add bromide to make a bromide bank -- even more important when using the Leslie's tabs or else you'll get some chlorine in addition to bromine. That's not a problem, but since you've got a bromine spa I presume you mostly want it to remain a bromine spa.