Help with refill on Bromine system

[walleye]

I refilled my Sundance Altamar yesterday. I followed the Bromine system listed here to the tee. Everything went as I thought it would. I added the Metal Sequester, raised TA to 105 using Baking Soda, Adjusted PH using Spa Down (dry acid?) from a strong 8 to 7.5, added calcium booster to get to around 200, I used 2 ounces of sodium Bromide powder
(says 99% pure) followed by 8 Ounces of 6% regular Clorox. Bromine test showed 12.5. I let circulate for a few hours and the level dropped to 9. I dropped two bromine tabs in the compartment and I let my daughter and two grand kids soak a few hours later for about 45 minutes after the temp rose to about 98F. This was all yesterday starting in the AM (I drained tub the night before). Now just a few minutes ago, I checked the bromine and it is zero. I use a Taylor K2106 kit. No even a trace of pink shows up, even with an extra dipper of indicator powder. Question is did I do something wrong? And more importantly do I need to drain and refill? I just added 6 ounces more of 6% regular bleach and the tub is circulating. Tub holds right at 400 gallons. I am bummed. The two bromine tabs I put in yesterday are still mostly full size?
Please let me know what I need to do.

Note:
I just tested after adding the 6 Ounces of bleach and circulating for 20 minutes and the bromine level is at 8.5 ppm. Not sure if this helps at all. Still need to know If I need to drain and refill. I want to be sure I have a sanitized tub.

 

[chem geek]

Welcome to TFP!

What you experienced is normal and you did the right thing. However, if those are truly bromine readings you are measuring (and with the K-2106 I assume you are using the units of measurement for bromine where with a 10 ml sample each drop is 1.25 ppm and with a 25 ml sample each drop is 0.5 ppm), then the implied spa size is 700 gallons. Is your spa really that large?

Two people soaking for 45 minutes in a hot (104ºF) spa would require the equivalent of 11.8 ppm bromine in 700 gallons so you can see how it could wipe out the 9 ppm you started with when they went into the tub. The tabs don't dissolve quickly enough to handle such bather load -- tabs are designed more for handling the background level in between soaks. After a heavy bather load, you need to add an oxidizer (such as bleach) to activate more bromine to handle the bather waste. Also, if the kids happen to urinate, then all bets are off and a lot more oxidizer would then be needed.

The rule for oxidizing bather waste is roughly that every person-hour of soaking in a hot tub requires 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock (43% MPS) to handle the bather waste and that this is independent of spa size. The 2 kids for 45 minutes is 1.5 person-hours.

Most people start out their soak with a lower level of chlorine (1-2 ppm) or bromine (2-4 ppm) and then add the needed amount of oxidizer right after their soak. That way they don't smell much chlorine or bromine during their soak while still handling the bather waste right afterwards and making sure they add enough so that they measure a low but not zero amount before their next soak. If you are concerned about person-to-person transmission of disease, then you'd start out with higher sanitizer levels so that it remains >0 during the entire soak, but if it's just your family then odds are you're exposing yourself to each others "stuff" in other ways. Commercial/public pools and spas have all kinds of strangers mingling including people who are sick and shouldn't be using such facilities so the requirements in those situations are necessarily more stringent and legally required.

 

[walleye]

Chem Geek, the tub is 395 gallons.

 

[chem geek]

In that case, you aren't getting the amount of bromine that would be expected either because the bromide bank is too low or the oxidizer (bleach) isn't as strong as you think or there was leftover stuff to oxidize that depleted the chlorine/bromine before you measured it or there is some sort of test measurement error. Even so, the basic principles of adding enough oxidizer/sanitizer after a soak so that you have a measurable residual by your next soak still applies.

 

[walleye]

Do I need to drain and refill? I am wondering if the sodium bromide powder is wasted and I have no Bromine bank? I did so many tests over and over I am convinced that is not the problem and the regular bleach says 6% on label so unless there is an error on label I have to presume my tub somehow got contaminated. I suppose the best is to decontaminate the tub with strong shock, drain and start over?

 

[chem geek]

I don't think it's contaminated -- the bromine level dropped too quickly right after you added oxidizer. Why don't you just proceed from here and see where things go. If you have any longer time between soaks, then you can measure, add, let mix for 10 minutes or so with circulation, then re-measure and see if things make more sense.

 

[mcaron74]

One other thing i have read on here somewhere is... Bleach does deteriorate over time so if you buy bleach at a discount store where it may be older on on the shelf longer, it may not be as potent as it was when it was new. Not saying that is yoru issue, but just throwing out ideas.