Newbie needs help with spa water chemistry problems

[Vesuvius]

pH of 7.4 and TA of 50 will be fine.

As long at pH is stable and above 7.2 the TA can be 50 or even 40. Let the pH be your guide if TA needs to be raised.

OK, got it--thanks!

 

[Methuselah]

OK, that makes me feel better about what I measured today, unless I tested too soon to get the full drop. How long do you wait until you test after leaving the tub?

I had to experiment with that. Next morning after an evening soak was probably the referee. I knew normal drop and demand and just fiddlefatrted around with additional dosing and next morning results.

Just keep ph below 8, chlorine above the minimum (extra so it can't ever be below), and note the demand. I test every 2 or three days, but when anything unexpected shows up, it's back to daily.

Biggest issues will always be letting ch drop too low and trying to hang onto old water when it's time to dump it (I'm guilty too...)

 

[Vesuvius]

I had to experiment with that. Next morning after an evening soak was probably the referee. I knew normal drop and demand and just fiddlefatrted around with additional dosing and next morning results.

Just keep ph below 8, chlorine above the minimum (extra so it can't ever be below), and note the demand. I test every 2 or three days, but when anything unexpected shows up, it's back to daily.

Biggest issues will always be letting ch drop too low and trying to hang onto old water when it's time to dump it (I'm guilty too...)

OK, thanks. Why is CH drop such a big issue? I thought CH levels basically remain unchanged save for replacing water loss.

 

[Vesuvius]

Did another 24-hr depletion test and FC dropped from 9.5 to 7.5 with no spa use. This 2.0 ppm depletion is the lowest I've seen yet, so perhaps Methuselah's thought that the filters could be the problem was on target (as I replaced them 24 hrs ago).

pH remains stable at 7.4. Still not enough CYA in via di-chlor (have added only 27 ppm so far, so about 7 more to go) to measure via my T-2006. Everything else is exactly where I want it, so if I settle into more reasonable daily demand numbers, I think I'll be in good shape for this batch of water.

 

[Methuselah]

Did another 24-hr depletion test and FC dropped from 9.5 to 7.5 with no spa use. This 2.0 ppm depletion is the lowest I've seen yet, so perhaps Methuselah's thought that the filters could be the problem was on target (as I replaced them 24 hrs ago).

pH remains stable at 7.4. Still not enough CYA in via di-chlor (have added only 27 ppm so far, so about 7 more to go) to measure via my T-2006. Everything else is exactly where I want it, so if I settle into more reasonable daily demand numbers, I think I'll be in good shape for this batch of water.

Demand seems decent. As for CYA I find it easier to weigh dichlor and compute it, then measure thereafter and compute tub gallons.

BTW, it's hard to measure low CYA values, but if you let half your sample evaporate it reads 2X so you're more on scale. Just divide by 2 for reading.

 

[Methuselah]

OK, thanks. Why is CH drop such a big issue? I thought CH levels basically remain unchanged save for replacing water loss.

I don't recall mentioning CH.

It rises as you replace evaporated water, lowers with what may rinse from filters or precipitate. Higher can help with foaming...

 

[Vesuvius]

I don't recall mentioning CH.

It rises as you replace evaporated water, lowers with what may rinse from filters or precipitate. Higher can help with foaming...

This was in your post above:

Biggest issues will always be letting ch drop too low and trying to hang onto old water when it's time to dump it (I'm guilty too...)

 

[Vesuvius]

Demand seems decent. As for CYA I find it easier to weigh dichlor and compute it, then measure thereafter and compute tub gallons.

OK, good. Yeah, that's essentially what I'm doing. Not in a big hurry to get to 30 given it's covered.

 

[Methuselah]

This was in your post above:

Oops, typo, chL...

 

[Vesuvius]

Oops, typo, chL...

Ahh, I see

 

[Vesuvius]

I've converted my spa to SWG via the Saltron Mini and am getting some weird FC data, so am wondering if anyone has any thoughts on what might be going on. My water has been perfectly balanced now for over a week--TA 50, pH 7.4-7.6, CYA 30, BOR 50, CH 120, Salt 2000. Before introducing the S Mini, I tried to establish constant temperature, no-use (covered w/ very little sun exposure--just when testing and adding di-chlor to get CYA up to 30) 24-hour FC decay rates as a baseline. My data there was odd but I understand that can happen a bit in the first few days after an Awe-some purge:

Day 1: 3.8 ppm drop; 36% decay rate
Day 2: 6.8 ppm drop; 80% decay rate
Day 3: 3.5 ppm drop; 25% decay rate
Day 4: 5.2 ppm drop; 50% decay rate (put in new filters after this test)
Day 5: 2.0 ppm drop; 21% decay rate
Day 6: 3.0 ppm drop; 40% decay rate
Day 7: 3.7 ppm drop; 32% decay rate

So, lots of variance but roughly 3.5-4.0 ppm drops per 24-hr period (in reading other threads on this topic it seems to me that the ppm drop measure is the important one for spas rather than the % decay rate, but please let me know if you disagree on that). This seems high to me but I haven't been able to find great rules of thumb in other threads other than some indications that 25% decay rates are ideal--I'd welcome any thoughts on that.

Then, I introduced the S Mini, which I set to run for 5 hrs in a 420 filled gallon tub. The S Mini documentation says that normal output equivalent is 32 grams (1.1 oz) of free available chlorine per day. Running this through Pool Math with 24-hr SWG Output of 0.07054792 lbs (i.e. 32 grams), 100% SWG % and 5 hours Pump Run Time provides expected FC addition of 4.2 ppm. Assuming a 4.0 ppm 24-hr decay rate per above, I'd expect to lose 0.8 ppm of FC during the 5-hr run-time, resulting in expected net additions of 3.4 ppm. I've now run two 5-hr cycles over the last 2 days and here's the data:

Day 1: 8.0 ppm pre-start; 10.5 ppm after-finish (5 hours later)--2.5 ppm net increase
Day 2: 7.5 ppm pre-start; 8.0 ppm after-finish (5 hours later)--0.5 ppm net increase (one difference here was that I added 2 oz of Aqua Clarity about 30 mins before the S Mini kicked on--this was the 1st time I've done this weekly addition)

I've confirmed the the S Mini timer mechanism is working correctly, as I observed the unit kick on and off 5 hrs later at the same times each day. I also observed that gas bubbles were being produced by the unit both immediately after it started and immediately before it kicked off.

So, what could be going on that I'm not getting expected net ppm additions here? It seems unlikely it could be normal variance in ppm decay, as these net increases with full 4.2 ppm gross additions would imply the following 24-hr decay rates:

Day 1: 8.2 ppm (1.7 ppm x 24/5)
Day 2: 17.8 ppm (3.7 ppm x 24/5)

I'd appreciate any thoughts--thanks!

 

[mknauss]

To me, you are overthinking this. As long as the FC stays about the minimum needed for your CYA level, it does not matter. I do not own a spa, so I would like @Mdragger88 to chime in.

 

[Mdragger88]

Just catching up on this thread,
As Marty said, you’re overthinking it a tad.
Keep fc above minimum at all times & ph in the 7’s & enjoy your tub.
Just Adjust the swg so that fc remains above minimum before you check again.
I noticed you have mentioned .5 or so cc’s consistently even after the purges. Try cleaning your beaker with alcohol & see if it goes away.
If not you still may have a little funky stuff going on which is leading to your slightly higher standby losses. No biggie, the aqua clarity weekly & keeping fc up will likely continue to improve it. If the cc’s increase & remain persistent its best to go ahead & do another purge ahead of schedule.
Take the listed output of the saltron mini with a grain of salt, forgive the pun
In such a small container of “people soup” doing an fc gain test is nearly impossible.
Most folks with your size tub settle on around 5hrs or so of run time to make up for standby fc losses. More if aiming to make up for bather loads. I have mine on a cheap mechanical timer so it comes on multiple times per day & provides more consistent fc.

I also noticed you mentioned the dichlor not giving quite the results you expected. What product are you using?
Does it say it’s 99% dichlor on the ingredients list?

 

[Vesuvius]

Just catching up on this thread,
As Marty said, you’re overthinking it a tad.
Keep fc above minimum at all times & ph in the 7’s & enjoy your tub.
Just Adjust the swg so that fc remains above minimum before you check again.
I noticed you have mentioned .5 or so cc’s consistently even after the purges. Try cleaning your beaker with alcohol & see if it goes away.
If not you still may have a little funky stuff going on which is leading to your slightly higher standby losses. No biggie, the aqua clarity weekly & keeping fc up will likely continue to improve it. If the cc’s increase & remain persistent its best to go ahead & do another purge ahead of schedule.
Take the listed output of the saltron mini with a grain of salt, forgive the pun
In such a small container of “people soup” doing an fc gain test is nearly impossible.
Most folks with your size tub settle on around 5hrs or so of run time to make up for standby fc losses. More if aiming to make up for bather loads. I have mine on a cheap mechanical timer so it comes on multiple times per day & provides more consistent fc.

I also noticed you mentioned the dichlor not giving quite the results you expected. What product are you using?
Does it say it’s 99% dichlor on the ingredients list?

Thanks, M'88! I've definitely been known to overthink things, but, after seeing FC additions of only 17%-73% of spec, it seemed reasonable to wonder if my unit is faulty. So, I wanted to check my math and/or make sure I'm not missing something, while the unit is under warranty. It would matter to me, even if I could turn the unit run times high enough to meet FC minimums, if the lifespan of the unit is shortened by 70% because of a defect in production rate that requires me to run the thing for 3x more hours/day. However, you've given me 2 bits of info that make me feel better about that--1) 5 hours/day is pretty common for standby FC maintenance, and 2) the listed output is unreliable. So, I'll turn off the brain and just go with it!

I did clean the test beaker with alcohol and have done a couple of CC tests. While I'm still getting a bit of pink color, it's probably half of what I seeing before using the aqua clarity and then doing the beaker clean. So, if I was measuring 0.5 before, it's probably more like 0.25 now. I'll definitely keep an eye on it, particularly as I take your advice and start actually using the tub

Yes, with 2 more days of measurements, it appears that 5 hrs run time is about right to make up for standby FC losses, so that's encouraging.

Yes, the di-chlor I'm using is 99%. It's actually worked as expected save for the one time after my only soak test, where I suspect there was more depletion from the soak that happened after I took the post-soak FC reading and that probably burned up some of the added di-chlor that I thought was going to increase FC levels.

Thanks again for all your help with this stuff--I've learned a ton reading your posts on other threads over the last couple years.

 

[Mdragger88]

If you’re getting a decent “cloud” from your unit it’s likely functioning properly. My experience with them has been a cell lifespan of approximately 18 months each time. Their tell of impending death is usually intermittently throwing the low salt light when there’s plenty salt in the water. They usually either produce “clouds” or they don’t.

Glad we could be of assistance!
Here’s a great way to show your appreciation & help keep the lights on around here

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[Vesuvius]

If you’re getting a decent “cloud” from your unit it’s likely functioning properly. My experience with them has been a cell lifespan of approximately 18 months each time. Their tell of impending death is usually intermittently throwing the low salt light when there’s plenty salt in the water. They usually either produce “clouds” or they don’t.

Glad we could be of assistance!
Here’s a great way to show your appreciation & help keep the lights on around here

Become a TFP Supporter

Help Support TFP Trouble Free Pool is run by a dedicated group of volunteers that … Read more…

www.troublefreepool.com

More good info--thanks!

Happy to show my appreciation--the lights will now stay on a little bit longer

 

[Methuselah]

What drives me nuts about using CC as an indication of "water sanitation health" is instruction variance, .5 ppm threshold, and tollerance of test results.

1. Add "last" drop, color goes from obvious pink to definitive clear. Still says do another.

2. Add "last" drop, color goes from slight pink to definitive clear. Still says do another...

You can't help but think in 2 that adding another drop after the last all but assures if there was CC around .5 you wouldn't (couldn't?) see it.

Conversely in 1, you have a compulsion to withhold the drop after last and if you do see CC wonder if your failure to add another drop pooched the test results.

Anyway, the results at .5 may not be accurate, and at or under .5 is supposed to be ok. I reckon after a while you do develop an "insight" on interpreting the result. I'm prone to over thinking it too...

BTW, your last numbers may suggest the filter was an issue. However, I'm just not capable of getting past the additions of aqua aqua Clarity or anything else --- simply put, it's just plain easiest to maintain proper chemical balance with LESS stuff in the water, especially when adding something unusual or unnecessary can bring mystery ingredients into the equation.

I agree with given advice, keep FC high enough that it can't drop to minimum. Also, keep FC high enough that it can't drop to minimum. Did I mention you should also keep FC high enough that it can't drop to minimum?

 

[Vesuvius]

What drives me nuts about using CC as an indication of "water sanitation health" is instruction variance, .5 ppm threshold, and tollerance of test results.

1. Add "last" drop, color goes from obvious pink to definitive clear. Still says do another.

2. Add "last" drop, color goes from slight pink to definitive clear. Still says do another...

You can't help but think in 2 that adding another drop after the last all but assures if there was CC around .5 you wouldn't (couldn't?) see it.

Conversely in 1, you have a compulsion to withhold the drop after last and if you do see CC wonder if your failure to add another drop pooched the test results.

Anyway, the results at .5 may not be accurate, and at or under .5 is supposed to be ok. I reckon after a while you do develop an "insight" on interpreting the result. I'm prone to over thinking it too...

BTW, your last numbers may suggest the filter was an issue. However, I'm just not capable of getting past the additions of aqua aqua Clarity or anything else --- simply put, it's just plain easiest to maintain proper chemical balance with LESS stuff in the water, especially when adding something unusual or unnecessary can bring mystery ingredients into the equation.

I agree with given advice, keep FC high enough that it can't drop to minimum. Also, keep FC high enough that it can't drop to minimum. Did I mention you should also keep FC high enough that it can't drop to minimum?

I haven't seen a good argument against the use of Aqua Clarity and I've seen some good ones supporting it. But I'm always open to changing my mind.