CYA level way too high - new hot tub owner

[Merocc]

Hello I need some assistance with my new hot tub. I purchased an Aquarest AR500 Premium (https://aquarestspas.com/product/premium-500-5-person-plug-n-play-spa-featuring-29-stainless-steel-jets-and-led-backlit-waterfall/). After some research, I opted to go for bromine. I tried to follow waterbear's 3-step bromine method. However, I ran into the issue of finding sodium bromide in Canada. I purchased 'brominating granules' fro my local store, which state they are 14.6% sodium bromide and 52.7% dichlor. For the past 2 weeks I have added about 10g/day of the granules. My bromine level was always very low (2ppm or less) when I tested before adding the granules. I thought it would be fine to just build my bromine bank for a few weeks as waterbear's thread suggested. However, I took a sample to my pool shop and the CYA levels are 118ppm.

I finally had enough of the granules and purchased a pure sodium bromide product from Amazon. The tub is 215 gallons, so it needs approximately 1oz to build a bromide bank. Since I was already adding the granules for 2 weeks, I only added a 1/2oz. I then added 12tbsp of 4% bleach. But my bromine level was still very low, around 1ppm. The alkalinity has dropped from 100ppm when I first filled it to 62ppm. pH is 7.5 currently.

I am so confused, I don't know where to start. Correct alkalinity? Add more sodium bromide?  Drain and refill my hot tub (maybe half) to get the CYA level down? 

[waterbear]

CYA doesn't matter in a bromine system. Once the chlorine oxidizes the sodium bromide into bromine sanitizer the effects of CYA are removed from the equation. Low bromine is to be expected when using a one step or 2 step bromine system which is why they require daily attention, much like a chlorine system.

[waterbear]

11 hours ago, Merocc said:

h. But my bromine level was still very low, around 1ppm. The alkalinity has dropped from 100ppm when I first filled it to 62ppm.

How are you testing your water. If you are using DPD then it is possible that your bromine is actually high and bleaching out the test. This could also explain the apparent drop in alkalinity since the indicator used for testing it is very prone to bleachout.

DId you purge the tub? it is also possible that there is biofilm in the plumbing consuming the sanitizer. FIrst step is to determine if your test results are bleaching out. My suggestion is to get an inexpensive 2 way test kit that uses OTO reagent for bromine and chlorine. You can tell it's OTO because the color blocks on the sanitizer test are shades of yellow. OTO will not bleach out, unlike DPD (shades of red on the comparator) and syringaldazine (used in many strips). Test with OTO and let me know if the color is yellow, deep yellow, orange, or brown and we can take it from there.

[Merocc]

I have been using OTO test the whole time (same kit I use for the pool). 

I added another 0.5oz of sodium bromide and then 6oz of bleach last night because the OTO test was a very faint yellow (around 0.3 on the scale in attached photo). After a little while I tested again and was getting 3 (brighter yellow).  I also have a bromine floater with tablets in the hot tub but it didnt seem to be doing much to raise the sanitizer levels.

I tested again just now and it looks like it's dropped to 1. 

pH has gone up to 7.8 so I'll add some miuratic acid. I guess keep adding bleach?

[waterbear]

 

20 hours ago, Merocc said:

am so confused, I don't know where to start

The place to start is a full set of test results that are NOT done with strips. Get them and post them.

Your test kit only has a chlorine scale. Multiply the reading by 2.25 to get total bromine.  How are you testing TA? I would recommend getting a Taylor K-2006 for both your pool and spa even though it's pricy in Canada. For bromine you would test FC and multiply the results by 2.25. This applies to OTO, DPD, syringaldazine, and FAS-DPD testing. You don't need to test a bromine system for CYA. OTO only tests  total chlorine or total bromine which is fine for a bromine system but for chlorine you really need to know both FC and CC.

From what you have said you have never gotten the bromine to shock level (over 10 ppm and up to 20 ppm. Get it to shock level and let the bromine drop below 10 ppm before entering the spa. 10 ppm would be darker then the 5 ppm block on your tester. There are OTO kits that have a scale that goes to 5 ppm chlorine/10 ppm bromine such as the K-1000 from Taylor or the 3 way (chlorine/bromine/pH) test kit from Blue Devil. However, I still recommend getting the Taylor K-2006 FAS-DPD test kit which will test FC, CC, Total bromine, pH with both acid and base demand, TA, CH and CYA (for your chlorine pool). Also, if the floater is not maintaining the bromine open it up more. I recommend this Pentair 335 floater since it is very adjustable:

IF you still cannot hold bromine then you need to purge. You mentioned it is a new tub and manufacturers wet test them when they are made. This leaves some water in the lines which can allow biofilm to grow.

 

[Merocc]

I have been using this Pentair test kit, not strips: https://a.co/d/0JMAuyW

I have also taken samples to the pool shop. Based on both, my most recent results are:

Cl: 1.0ppm

pH: 7.8

Alk: 90ppm

Hardness: 171ppm

Is the best way to get the bromine to shock level (10ppm) is adding more bleach? 

[waterbear]

If you atmrexyesting bromine multiply the chlorine reading by 2.25. 

7 minutes ago, Merocc said:

Is the best way to get the bromine to shock level (10ppm) is adding more bleach? 

Yes, but DO NOT TRY TO TEST pH or TA until bromine is below 10 ppm because the pH will read false high and the TA false low because of a chemical interference between the high sanitizer and the indicator dyes.

[Merocc]

Thanks for all the help. I added another 10oz of 4% bleach. Here's the latest result.

So no need to worry about the high CYA? I wasn't sure if it would have any negative consequences with a bromine spa.