First Week On Dichlor Then Bleach, Issues

[mikef135]

Hi All,

I'm on my first week of chemgeek/Nitro's dichlor then beach method after the decontamination. Just did a test on my 425 gallon spa:

shocked to 10ppm FC with bleach yesterday night

did the borox/acid last week (25oz borox/17 oz dry acid)

tested just now:

8ppm FC

TA = 80ppm

ph=7.8 (maybe 7.9 - seems to stay on the high side for me)

CH=160ppm

temp is from 100-102 (my tub is set for 100 but is on the south side of my home in Southern California so is getting heated during the day up to 102 sometimes) ... I think the pumps are also heating it when using (heat from (2) 5hp pumps)

I've added 37.5ppm of CYA with the dichor

Tried to run the CYA test in my taylor k-2006 kit ... could still see that black dot even with the tube filled all the way up

Tried an Aquacheck chlorine test strip and that is showing 0 CYA although tough to read

Is it pointless trying to test for CYA? Is my CYA getting burned off or something due to my environmental conditions of the tub itself (south side of home in the heat) ... the cover is in good condition (previous owner said it was an upgraded one - looks pretty solid)

So far it has been happy tubbing with clear water ... just checking in for any tips

Also, during the decon process I stuck some seal-a-leak in from Spa Depot (after the spa flush and drain but before the 50ppm FC step). It fixed one leak I saw but still have a slow seeping leak somewhere. I added 1" of water approx yesterday. Not sure how much of that is due to evaporation or leaving thru bathing suits (have used the tub everyday this week with wife) ... I have a 7'x7'x39.5" tub

Thanks,

-Mike

[chem geek]

For the 37.5 ppm CYA, do you mean you've cumulatively added around 42 ppm FC using Dichlor? You don't add that all at once, but just use Dichlor initially for a week or so until the CYA builds up. If one wanted to add CYA right away initially, then one could use pure CYA or Instant Pool Water Conditioner, but most people just use Dichlor at normal daily chlorine usage rates until the CYA build up.

That is strange that the CYA isn't showing up. Is the CYA test showing cloudy but just not cloudy enough to have the black dot be obscured? See this link for what the test looks like when the black dot disappears.

As for your pH tending to rise, let the TA drop lower as you add acid to lower the pH. Let it get to 60 ppm or even 50 ppm. The Borates will help buffer your pH so your TA does not need to be higher and it only makes the rate of pH rise go faster.

[mikef135]

For the 37.5 ppm CYA, do you mean you've cumulatively added around 42 ppm FC using Dichlor? You don't add that all at once, but just use Dichlor initially for a week or so until the CYA builds up. If one wanted to add CYA right away initially, then one could use pure CYA or Instant Pool Water Conditioner, but most people just use Dichlor at normal daily chlorine usage rates until the CYA build up.

That is strange that the CYA isn't showing up. Is the CYA test showing cloudy but just not cloudy enough to have the black dot be obscured? See this link for what the test looks like when the black dot disappears.

As for your pH tending to rise, let the TA drop lower as you add acid to lower the pH. Let it get to 60 ppm or even 50 ppm. The Borates will help buffer your pH so your TA does not need to be higher and it only makes the rate of pH rise go faster.

Yes to your first question ... I built that up over last week using dichlor.

The CYA test is showing cloudy but I can still see that black dot when the tube is full. It is somewhere between pictures mid test and end test at that link you sent me.

[PaulR]

IIRC the K-2006 CYA test measures down to 30ppm? so you're probably in the 20-30 range.

Measuring dichlor in the small amounts needed in a hot tub is pretty error-prone. I mean, CYA 37.5 would be something like 4oz (by volume) dichlor over the course of a week, or on the order of 1/2 oz per day. Measuring 1.0 tablespoon of dichlor is not easy. Small measurement errors could easily have added up to a smaller total than you thought.

I would just use dichlor a little while longer and chalk it up to measurement error.

--paulr

[chem geek]

Also, for the CYA test, you want strong indirect lighting. The best is to stand outside with your back to the sun with your body shading the CYA tube held in front of you looking down into it. If you have sun or other bright light directly hitting the tube, you will get a falsely low reading. If indoors, have many lights turned on but don't stand under or in front of any specific lamp.