In Ground Spa with no Cover: blue solar blanket only

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J

jkarn

Well-known member
Apr 16, 2023
52
Chicago, IL
Pool Size
12000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Salt & Swim 3C
Hi All, I'm wondering if there's any reason to use a higher ppm for chemicals like CYA or change anything with regards to the Sticky "How do I use Chlorine in my Spa?". The Spa is a 550 gallon, fiberglass, shell that's in-ground about 2/3; i.e. it sticks up a foot or 2 out of ground. It is totally separate from the pool and equipment is in my sig. Because of its 10ft diameter, I haven't purchased a proper cover. I only use a blue solar cover when we're not using it. Should I treat this like a pool or spa? With the heat, I lean toward spa but it is exposed to direct sun during the day. Or really... Am I just over thinking this and get the chemicals to the ranges in the PoolMath app and leave it at that?
 
So I've been monitoring this spa pretty closely: keeping temperature relatively low at 98F. CYA is at 40, but my chlorine keeps dropping to 0 from day to day. Currently, I haven't been putting the solar blanket on and it gets direct sunlight starting around 7:30am until late afternoon. All other levels are within range. Very little usage yet this year.

Before adding more CYA, what would you all suggest to help me keep FC more stable? I added Calcium yesterday, just haven't tested levels yet.

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Hot Tub
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Build Type: Fiberglass
Volume: 550 gallons
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Latest Test Result Summary:
FC: 3.0 (11 hours ago)
CC: 0.5 (23 hours ago)
pH: 7.5 (23 hours ago)
TA: 90 (23 hours ago)
CH: 200 (23 hours ago)
CYA: 40 (23 hours ago)
==========================================
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Test Results 05-18-2024 @ 08:55 PM
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Free Chlorine: 3.0

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Test Results 05-18-2024 @ 08:54 PM
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Free Chlorine: 3.0

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Chemical Addition 05-18-2024 @ 08:39 AM
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+ 2.5 FluidOunces of Bleach

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Chemical Addition 05-18-2024 @ 08:39 AM
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+ 4.1 Ounces of CalciumChloride

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Test Results 05-18-2024 @ 08:22 AM
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Free Chlorine: 0.5
Combined Chlorine: 0.5
pH: 7.5
Total Alkalinity: 90
Calcium Hardness: 200
CYA: 40

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Test Results 05-18-2024 @ 07:52 AM
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Free Chlorine: 1.0
Combined Chlorine: 0.0
pH: 7.3
Total Alkalinity: 90
Calcium Hardness: 325
CYA: 70

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Test Results 05-17-2024 @ 03:39 PM
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pH: 7.5

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Maintenance 05-17-2024 @ 03:30 PM
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Vacuumed, Cleaned Filter, Brushed

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Chemical Addition 05-17-2024 @ 08:21 AM
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+ 0.9 Ounces of DryAcid

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Chemical Addition 05-17-2024 @ 07:54 AM
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+ 26 Ounces of DryAcid

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Test Results 05-17-2024 @ 06:03 AM
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Calcium Hardness: 300

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Test Results 05-17-2024 @ 05:54 AM
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Calcium Hardness: 225

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Chemical Addition 05-16-2024 @ 08:14 PM
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+ 14 Pounds of CalciumChloride

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Chemical Addition 05-16-2024 @ 08:12 PM
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+ 12 Ounces of CalciumChloride

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Test Results 05-16-2024 @ 08:42 AM
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Free Chlorine: 3.0
pH: 7.8

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Test Results 05-16-2024 @ 08:40 AM
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Free Chlorine: 5.0
pH: 7.5

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Chemical Addition 05-16-2024 @ 08:36 AM
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+ 2.2 FluidOunces of Bleach

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Test Results 05-16-2024 @ 08:23 AM
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Free Chlorine: 1.0
Combined Chlorine: 0.5
pH: 7.8
Total Alkalinity: 90
Calcium Hardness: 175
CYA: 40

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Maintenance 05-16-2024 @ 06:24 AM
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Cleaned Filter, Brushed

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Test Results 05-15-2024 @ 11:49 AM
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Free Chlorine: 4.0

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Test Results 05-15-2024 @ 11:47 AM
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pH: 7.5

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Chemical Addition 05-15-2024 @ 10:52 AM
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+ 18 FluidOunces of Baume31

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Chemical Addition 05-15-2024 @ 10:02 AM
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+ 1.4 FluidOunces of Bleach

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Test Results 05-15-2024 @ 10:01 AM
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Free Chlorine: 1.5
pH: 7.8

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Test Results 05-15-2024 @ 09:59 AM
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Free Chlorine: 5.0
pH: 8.2

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Test Results 05-14-2024 @ 12:12 PM
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Free Chlorine: 5.0
pH: 7.8

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Test Results 05-14-2024 @ 12:10 PM
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Free Chlorine: 3.0
pH: 7.5

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Chemical Addition 05-12-2024 @ 06:41 PM
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+ 1.7 FluidOunces of Bleach

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Test Results 05-12-2024 @ 08:29 AM
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Free Chlorine: 5.5
Combined Chlorine: 0.0
pH: 7.5
Total Alkalinity: 90

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Test Results 05-12-2024 @ 08:20 AM
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Free Chlorine: 7.0
Combined Chlorine: 0.0
pH: 7.5
Total Alkalinity: 110
 
jkarn said:
Before adding more CYA, what would you all suggest to help me keep FC more stable? I
Click to expand...
FC won't be stable if it's exposed to UV like a traditional pool. You will swing up to 4 ppm daily in the peak season. I'm due east of you and see high loss with full sun all day.

*Then* there is bather waste, or as I like to call it, people soup. 2 people in your hot tub is the equivalent of 44 people in your pool. And they would be cooling down, not heating up and being exfoliated. Think how quickly your pool would be utterly nasty with 44 swimmers, and yet, it's no thing to go have a soak with the spouse.

When was the last time you changed the water ? As it's own system, it needs to be dumped and refilled like a traditional hot tub. The robust plumbing may extend your lifespan a little, maybe to 6 months instead of 3, but it'll get away from you at some point.
 
Newdude said:
FC won't be stable if it's exposed to UV like a traditional pool. You will swing up to 4 ppm daily in the peak season. I'm due east of you and see high loss with full sun all day.

*Then* there is bather waste, or as I like to call it, people soup. 2 people in your hot tub is the equivalent of 44 people in your pool. And they would be cooling down, not heating up and being exfoliated. Think how quickly your pool would be utterly nasty with 44 swimmers, and yet, it's no thing to go have a soak with the spouse.

When was the last time you changed the water ? As it's own system, it needs to be dumped and refilled like a traditional hot tub. The robust plumbing may extend your lifespan a little, maybe to 6 months instead of 3, but it'll get away from you at some point.
Click to expand...
It was freshly filled end of April. We don't keep it open in the winter and do a full drain when we close the pool; i.e. we treat it like a smaller and hotter pool.
 
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Ok so with fairly new water it hasn't gone south yet.

You have 3 choices:

Traditional spa cover : see little loss besides residual bather waste

Solar cover : see UV loss somewhere in the middle of the 2, plus residual bather waste

Open air : see full UV loss like the pool, and higher residual bather waste.

40 CYA is plenty for Chicago unless you convert the spa to salt like the pool.
 
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Newdude said:
Ok so with fairly new water it hasn't gone south yet.

You have 3 choices:

Traditional spa cover : see little loss besides residual bather waste

Solar cover : see UV loss somewhere in the middle of the 2, plus residual bather waste

Open air : see full UV loss like the pool, and higher residual bather waste.

40 CYA is plenty for Chicago unless you convert the spa to salt like the pool.
Click to expand...
Ok. I'll get that solar blanket on today and see what happens. It's new, so I have to cut it. The problem with a traditional cover is the cost and where to store for a 10' diameter fiberglass shell. Options have been limited.

Note: I'm also going to try adding borates (boric acid method) later today simply to help with the pH and see if the water is actually more "silky"
 
jkarn said:
Options have been limited.
Click to expand...
Oh I fully agree / get it. :) But unless you pop a tent over it, you'll see full loss without the traditional cover. (Or partial loss with a solar cover).
jkarn said:
try adding borates (boric acid method) later today simply to help with the pH and see if the water is actually more "silky"
Click to expand...
I tell ya. I had them back in the day and my pool was amazing compared to everyone else's. Anywhere. We all but stopped using any pool but our own.

When I stopped using them I saw/felt no difference and chalked it up to the salt being the reason for the 'feel like you took a shower' instead of the 'feel like you need a shower'.

Then we moved and built pool #2 and I went over a week as a liquid chlorine pool and saw no difference again before adding the salt. I now consider it that i owe all TFP LC pools a humble apology. (Which I give here again today...... guys, I'm sorry.) Its the TFP balanced water that feels amazing, not the salt or borates IMO. Maybe it fixes screwups for the non TFP folks. I can't speak to that. Lol.

It's a cheap experiment in a hot tub, will probably help the insane spa Ph rise, and might have feel different as well. There no reason *not* to try and I look forward to your long term assessments.
 
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Another note: I've been trying a "liquid solar cover" as well. It's clear that it's helped in the pool, but it doesn't seem to have helped in the spa. The pool is very irregularly shaped, so it's too much hassle to get a solar cover cut and on it.
 

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