initial readings from K-2005

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darin.brown

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Oct 15, 2015
187
DFW, TX
still no plaster yet but I did go ahead and test the initial fill for the standalone hot tub. using the Taylor K-2005 that the PB provided.

pH would have read greater than 8.0 when I tried to match against the color scale. will likely re-test to make sure I was doing that correctly
TA 130
CH 110

FC between a 2 and a 3, though the TC appeared to read a solid 2 which doesn't make sense since FC should be less than TC?
CYA is less than 30 as the black dot never disappeared and I got to the top of the 9ml mark and couldn't keep adding drops.

I should note that we hadn't heated the water up yet when I grabbed the sample. It does appear that chemgeek's sticky assumes the temperature is around 100. is that going to impact my test results?

We'll be doing dichlor in the hot tub and SWG in the pool (almost ready for plaster) but wanted to get the spa fill squared away. Looking thru chemgeek's sticky on using chlorine for the hot tub it looks like we may be able to leave the CH where it is (although it appears 130-150 is ideal).

Looks like the first order of business is getting that TA lower (< 50 ppm)? So we're looking at adding enough acid (pool chemicals came with some MA so I suppose we'll break into that). So we'd add enough MA to get the pH down to 7.0, keep aerating and see if the pH raises again to >7.8, then add acid/test/repeat until pH settles in at 7.6 and stays there.

I guess I'll start with getting the pH to 7.6 and see what the TA is and go from there. Is it critical that I get the water temperature to around 100 before starting this?
 
I read through the link - a summary of spa water management by user Nitro, with additional posts by chem geek.

Regarding your question about water temperature, I don't believe that will affect your test results; however, it does change the calculated CSI parameter. Try playing with PoolMath to get a better feel for this.

I'll point out that the link does not recommend TA below 50 ppm. In fact, it cautions against pH instability if you go much below 50. So, lower TA carefully as you get down near that number. Did you understand the recommendation to aerate after adding MA (you did mention aeration, but I wanted to make sure).

Regarding the FC and TC values you report, yes, FC + CC = TC, so TC is always >= FC. I haven't used the DPD test that (I believe) is part of the K-2005, but it would probably be worth reviewing the procedure for that test.
 
I've started the process of lowering pH and TA by adding MA, aerating, repeat, etc.. and have gotten my TA down to 100 at last check. pH remains around 8.0 after latest aeration. my FC is still between 1-2 but I'm worried it might drop down to 0 with the spa cover off as I work on lowering the pH and TA. Should I go ahead and raise FC up via dichlor in the interim so I don't risk algae if the FC drops to 0? The notes above mention get the water balanced first before shocking to get the FC up to 10 but I don't want to risk FC dropping to 0.

my CYA is still less than 30 (tube is full and black dot still very visible so it's likely near 0) so I'm thinking a lone dose of dichlor to get my FC up as a continue to balance wouldn't have an adverse effect of my CYA. thoughts?
 
Yes, keeping FC up in a hot tub is important to prevent bacterial build up. FC should never drop to 0. Bacteria will quickly grow in a hot tub if given a chance. Bacteria colonies can double every 20 minutes in a hot tub.
 
I know of no reason to let FC drop while you work on alkalinity and pH. If you do add chlorine via dichlor, keep in mind that dichlor will lower pH. Also, keep track of how much dichlor you add - then you can calculate CYA, rather than just going by the black dot test (which is a challenging test to read accurately).
 
darin.brown, I just emptied and refilled my hot tub 2 weeks ago and finally started the TFP method after studying the Chem Geek link that you posted. My alkalinity and Ch were low (both at 30), so while I worked on balancing that with baking soda and calcium increaser I also started adding dichlor immediately to start raising CYA. It worked just fine and everything was balanced, including CYA, in about 6 days, with adding about 1 tablespoon of dichlor each day (testing each day of course).

Now have switched to liquid bleach and to be honest, my hot tub has never ever been this clear. Love this method :)
 

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as an update. my TA is down to 50 but the pH remains >8.0 after a round of aeration. I plan on testing it again in the AM to see what it is w/o a recent aeration. if the pH is down around 7.4-7.6 when I measure in the AM but still drifts up to > 8.0 after turning on the spa jets for 30 minutes, what's the best course of action? would continuing to add acid (I'm using dry acid) to get the pH down and a subsequent dose of baking soda to keep the TA at 50 be the best option?
 
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