Hot tub beginner questions

Sep 1, 2021
10
Lincoln,CA
After finding this site I drained my hot tub and started over yesterday. Had a few questions that I think I know the answer to, but wanted to run it by everyone here.

Hot tub specs: 515 gallon volume ozonator. Ozone runs only when main filter pump is running (minimum of 4 hours a day, plus any time it’s heating). I’m following the dichlor/bleach method recommended on this site.

After filling I did a water test with my K2006C:
FC 1.6 (tap water has a small amount, plus leftover from less than full draining)
CC 0
PH 7.5
TA 30
CH 20
CYA 0 (assuming it’s zero, I can see the dot with the test tube full, so it’s certainly less than 30).
I dosed with 1oz of dichlor to bring the FC to 10, and 3.6oz of baking soda to bring the TA to 60, then closed it up for the night to heat up to 100F.
About 12 hours later the FC dropped to 8, and another 10 hours later it was 6.5. My wife and I soaked for about 45 mins and it had dropped to 4.5. I dosed with 0.5 oz of dichlor to raise the FC to 8. CYA is probably 10-15, but too low to measure accurately. Everything else stayed about the same, TA dropped by 10, but I’m assuming that’s within the margin for the tests so leaving that for now. I have some CH increaser on order to balance the water so don’t want to raise TA too much yet. Also have some GentleSpa coming that I’ve seen recommended.
My questions:
1) Does the drop in FC over those timeframes make sense with my setup? I’ve seen estimates of 25/50% loss a day for hot tubs without/with ozone, so going from 10 to 6.5 seems to make sense.
2) When testing for CC, the sample turned the faintest shade of pink after putting in the DPD reagent. A single drop of the titrating agent cleared it up immediately. Does this count as .5 CC? Should I retest at the .2ppm sensitivity?
3) When getting in tonight at 6.5 FC, the water had a bit of chlorine smell. Is this due to the low CYA for 6.5 FC? It wasn’t bad enough to need to get out, just enough that it was noticeable.
4) Is it a problem to dose FC over the recommended FC for my CYA each night, knowing that it will drop by the next use due to ozone and off gassing? Other than the extra cost, which I don’t mind.
5) Is it safe to soak with the FC at SLAM level for my CYA? If it smells a bit I can deal with that.
6) What should I do if I’ll be away for enough days that the FC may drop below 1? Before finding this site I would have thrown a floater in there but know now that will result in too much CYA. Should I dose FC to the SLAM level (or more) and turn the temperature down? Turning off the ozone isn’t practical since it’s tied to the main filter pump.
Thanks!
 

jseyfert3

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Oct 20, 2017
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1) Does the drop in FC over those timeframes make sense with my setup? I’ve seen estimates of 25/50% loss a day for hot tubs without/with ozone, so going from 10 to 6.5 seems to make sense.
It doesn’t seem super unusual, but I’ve had a SWCG and lost track of normal FC loss off the top of my head.

2) When testing for CC, the sample turned the faintest shade of pink after putting in the DPD reagent. A single drop of the titrating agent cleared it up immediately. Does this count as .5 CC? Should I retest at the .2ppm sensitivity?
It means you have 0.5 or less PPM of CC. There’s no reason to figure test that more sensitively.

3) When getting in tonight at 6.5 FC, the water had a bit of chlorine smell. Is this due to the low CYA for 6.5 FC? It wasn’t bad enough to need to get out, just enough that it was noticeable.
I don’t think so. Chlorine smell is nearly always CCs. My 12.5% liquid chlorine smells like chlorine, but different than CCs and surprisingly not pungent for being 125,000 ppm. This really indicates the chlorine smell in pools is CC, not FC.

In my pool at SLAM levels of FC the water is completely oderless. I’ve been asked if my pool has chlorine because it doesn’t smell.

OTOH my spa usually has at least some smell due to CC. The pool gets tons of UV from the sun, has a ton of surface areas for offgassing, and is lightly loaded with bather waste for the size. None of which are the case for the hot tub.

4) Is it a problem to dose FC over the recommended FC for my CYA each night, knowing that it will drop by the next use due to ozone and off gassing? Other than the extra cost, which I don’t mind.
Feel free to dose up to the SLAM level every time if you want. That is my typical SOP for dosing after a soak.

5) Is it safe to soak with the FC at SLAM level for my CYA? If it smells a bit I can deal with that.
Yes, certainly. Again the smell will be from CCs not the FC.

6) What should I do if I’ll be away for enough days that the FC may drop below 1? Before finding this site I would have thrown a floater in there but know now that will result in too much CYA. Should I dose FC to the SLAM level (or more) and turn the temperature down? Turning off the ozone isn’t practical since it’s tied to the main filter pump.
For small uses a floater could work. Just need to watch CYA levels. Spas have much higher breakdown of CYA than pools, will likely need 10-15 ppm of CYA added a month.

Best thing is a SWCG. I have a Saltron Mini, it maintains FC between uses, I just manually dose FC after a soak to take care of bather waste.
 
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Mdragger88

Bronze Supporter
Jun 1, 2018
2,954
Hernando, Ms
Just to add to things mentioned above
- leave the cover open a few minutes to let the cc’s off gas before getting in & it probably won’t be so noticeable
- when my cya is low (below 15ppm) higher levels of fc (above 5) can feel harsh
I don’t usually notice it upon initial fill (i try to dose sparingly w/ dichlor due to its acidic effects) but rather later down the line when cya needs to be replenished (as it breaks down over time w/ high temp) so don’t forget to test for it periodically & use some dichlor to bump it back up.
- i have no issues soaking at slam level but u may not wanna wear your best suit.
Fc level drops the moment u put your toe in anyway due to how heavy the bather load is in such a small amount of water & obviously this occurs faster when there’s more people
- once you get an idea of how much fc your tub consumes per day when it’s un used you could then use that # x’s how many days you’ll be away to dose for vacations etc.

I too have a saltron mini, it’s definitely worth every penny & it keeps my fc levels pretty even all the time as I have it on a timer so it comes on multiple times a day. I just need to dose when i have extended soaks or if it’s more than just me soaking.
When i go on vacation i just turn it down to prevent my fc from becoming too high because no one will be using the tub.
 
Sep 1, 2021
10
Lincoln,CA
Thanks.

The smell wasn’t a super pungent chlorine stink, just a mild scent (basically a mild version of the bleach I have). Don’t think it was CC since it smelled right when o opened it after a fresh fill (may have been trapped off gassed chlorine now that I think about it).

I also tested my tap water and get the faintest pink hue when doing the CC test. I might be taking too long to jot down the number of drops, add the DPD reagent, then add more drops of titrating agent also
 
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Mdragger88

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Jun 1, 2018
2,954
Hernando, Ms
If you let it sit it will become pink again & skew your results.
You’ll get the hang of it & become quicker the more u get used to testing.
 
Sep 1, 2021
10
Lincoln,CA
Is there a point where the FC ppm would be damaging to the hot tub if I dosed it up for an extended time away? If my FC use is around 65% per day, I’d need to start with 75ppm if I were gone for 10 days. Or is the FC loss more of a steady number and not a percentage (thought I had seen percentages mentioned in other threads).

I’ll look into a SWG for longer term care, but want to get the hang of this first. When I bought the hot tub I asked about salt and the sales guy said that ends up corroding the internals of the hot tub. Can I assume he was just ignorant (or actively lying so I’d buy chemicals from him)?
 

jseyfert3

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Oct 20, 2017
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The general consensus is the salt needed won’t cause any noticeable increase in any corrosion. I’ve only been running salt for a year or so, no issues seen. My tub is 2008, unsure if the previous owners changed anything.

I had to replace a pump but that was because the pump seal started leaking which destroyed the bearing, but that has nothing to do with salt.

Others here have run pools/hot tubs for years and years with no issues.

I’lol never not have a SWCG for my tub now that I have one. And when I upgrade my Intex pool equipment I’ll be adding a SWCG to my pool as well. It’s great to have a constant source of chlorine without (much) manual additions.
 
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jseyfert3

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Oct 20, 2017
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Also to answer your original question I certainly wouldn’t crank the FC up to 75. Usually you shouldn’t try to take it over the SLAM level.

Without a SWCG you could try a floater, though I’m not sure how fast trichlor dissolves in hot water. Other things that help is ensure minimal load, so don’t soak the night before you leave. Bring up the chlorine levels right before you leave. Drop the tub temperature.
 
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Mdragger88

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Jun 1, 2018
2,954
Hernando, Ms
That seems like alot of consumption- especially for an un used clean tub. You definitely don’t wanna go to 75ppm. Based on your 1st post above it sounds like it eats about 3 ppm per day so if u went away for 5 days that’s about 15ppm - if your cya is in the 30-40 range that’s about slam level. The longest I’ve ever been away was a week but i usually have family come by mid week & check the mail & the skimmer on my pool, I imagine if needed they would be able to pour a pre measured amount of bleach in the hot tub too. Not sure if you have anyone who might be able to do this for u or not.
I have had my tub almost 3 years- i have always had a swg. From what I understand only certain types of heaters that are not titanium are prone to corrosion due to normal salt levels. I don’t believe mine is titanium based on the fact i have a fairly inexpensive plug & play tub but i am prepared to replace it if it goes out & have sourced a replacement. It is worth it to me considering the convenience the swg allows. You should be able to look yours up & find out what it is made of
 
Sep 1, 2021
10
Lincoln,CA
Thanks again everyone. I have everything pretty much dialed in. Need to bump the CH up just a bit, and I’ll have 30 CYA I’m the next few days of using dichlor then I’ll switch to bleach.

I’ve seen borates be suggested a few times. What is the overall effect? Is there any reason not to use it?
 

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Mdragger88

Bronze Supporter
Jun 1, 2018
2,954
Hernando, Ms
Borates help buffer the rise of ph , the easiest & cheapest way to get them in the water is granular boric acid. Most here get that from duda diesel.
i use it in my pool also so i buy a big bucket but they sell various amounts.
You want to have your ta in the 50 range before adding.
 

A.O.

Well-known member
Apr 12, 2016
493
Kershaw, South Carolina
It doesn’t seem super unusual, but I’ve had a SWCG and lost track of normal FC loss off the top of my head.


It means you have 0.5 or less PPM of CC. There’s no reason to figure test that more sensitively.


I don’t think so. Chlorine smell is nearly always CCs. My 12.5% liquid chlorine smells like chlorine, but different than CCs and surprisingly not pungent for being 125,000 ppm. This really indicates the chlorine smell in pools is CC, not FC.

In my pool at SLAM levels of FC the water is completely oderless. I’ve been asked if my pool has chlorine because it doesn’t smell.

OTOH my spa usually has at least some smell due to CC. The pool gets tons of UV from the sun, has a ton of surface areas for offgassing, and is lightly loaded with bather waste for the size. None of which are the case for the hot tub.


Feel free to dose up to the SLAM level every time if you want. That is my typical SOP for dosing after a soak.


Yes, certainly. Again the smell will be from CCs not the FC.


For small uses a floater could work. Just need to watch CYA levels. Spas have much higher breakdown of CYA than pools, will likely need 10-15 ppm of CYA added a month.

Best thing is a SWCG. I have a Saltron Mini, it maintains FC between uses, I just manually dose FC after a soak to take care of bather waste.
So jseyfert about how much chlorine do you add after a soak?? I do that now, add chlorine after a soak, but I dont have the SWG and just wonder how much chlorine I would save with the SWG.
 

jseyfert3

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Oct 20, 2017
1,791
Southern WI
So jseyfert about how much chlorine do you add after a soak?? I do that now, add chlorine after a soak, but I dont have the SWG and just wonder how much chlorine I would save with the SWG.
About 4-5 oz typically. Based on testing, I’ve determined that the FC is zero after a typical use of ours. So eventually I just started assuming it was zero, and added the PoolMath recommended amount of chlorine to take it from 0 to SLAM level upon getting out, which at 30 ppm CYA is about 5 oz of 12.5% for our tub.

IMO a SWCG for a tub isn’t about saving chlorine overall, it’s about not having to manually add chlorine in-between uses.
 
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Mdragger88

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Jun 1, 2018
2,954
Hernando, Ms
I do the same as @jseyfert3 - except my tub is smaller so it is usually about 1-2oz.
or sometimes i just push the button while i’m in there - depends on my settings & if it’s just me. Mine never goes to zero usually.
 

A.O.

Well-known member
Apr 12, 2016
493
Kershaw, South Carolina
About 4-5 oz typically. Based on testing, I’ve determined that the FC is zero after a typical use of ours. So eventually I just started assuming it was zero, and added the PoolMath recommended amount of chlorine to take it from 0 to SLAM level upon getting out, which at 30 ppm CYA is about 5 oz of 12.5% for our tub.

IMO a SWCG for a tub isn’t about saving chlorine overall, it’s about not having to manually add chlorine in-between uses.
Wow, I add less than that without a SWG! 450 gal tub, 2-3 oz per soak is what I generally add. And between uses is from am to pm everyday.
 

jseyfert3

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Oct 20, 2017
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Wow, I add less than that without a SWG! 450 gal tub, 2-3 oz per soak is what I generally add. And between uses is from am to pm everyday.
It’s usually at least two of us, we don’t typically shower beforehand and it’s usually two hours minimum soak if we do get in. Sometimes it’s 4, or even more people, though in that case I try to remember to test and add during the use in addition to after the use.
 

A.O.

Well-known member
Apr 12, 2016
493
Kershaw, South Carolina
It’s usually at least two of us, we don’t typically shower beforehand and it’s usually two hours minimum soak if we do get in. Sometimes it’s 4, or even more people, though in that case I try to remember to test and add during the use in addition to after the use.
Yeah, its normally 2 for us also and soaks are usually 2 jet cycles or half an hour. We do not do the pre tub shower most of the time either . I cant imagine soaking for 2 or more hours.. ya must look like prunes when you get out! :D