To stabilize or not to stabilize, that is the question...

[styopr]

Resurrecting an old question posted here on whether or not to add CYA to a hot tub. The reasons given for adding CYA conditioner to a covered hot tub in older posts seemed to be comfort-only. Without CYA, the reasoning goes, having the extra hypochlorous acid floating about at the necessary sanitary level of 3-4ppm is just uncomfortable for some folks, and possibly not needed in terms of sanitation. However, I have never used CYA in my tub, appreciate the extra chlorine (especially when you get 6 dirty kids in the tub) and appreciate the extra ease in shocking. Doesn't take much to bring it to slam level. Super easy to keep clean! Never had an issue. It has never been uncomfortable to me (spending 2+ hours in there) and no one else has complained. I have a SWG and 450 gallon tub. The SWG keep a minimum level of chlorine going. I add bleach when demand increases due to bather load using it up. Me, with the hot water, high bather load, and grossness level, I'll take all the extra hypochlorous acid I can get..

My Question:
Since 3-4ppm, and sometimes higher FC, has never uncomfortable for me or guests (the only reason given for justifying CYA) is there any real data as to safety?

Since EPA considers 4 PPM chlorine safe for DRINKING WATER, what hard data is there that 4ppm is unsafe (or even uncomfortable in blind or double blind studies) at this level without CYA. I have actually measured 4 PPM at the Tap in Minneapolis (no doubt after an event, since I only got that once). I doubt I'd ever have known that if I didn't randomly test out of curiosity...

However EPA calls this level safe to DRINK, bathe in, etc.. I'd be curious to know if there was science behind justifying for "comfort" other than yeah maybe it's not necessary.

Asking because I'm thinking about adding CYA, but then why? if no one is uncomfortable and it's so easy to keep clean...

 

[newdude]

Asking because I'm thinking about adding CYA, but then why? if no one is uncomfortable and it's so easy to keep clean...

For one, if the tub is ever used in the daytime, the sun will eat 450 Gallons worth of treated tub water in a couple minutes. It wouldn't even matter how high you treated.

If it's an evening only activity as most usually are, then there is no concern.

As far as the evidence goes, me never seeing data doesn't mean it's not out there, but the only thing I've ever seen about hot tub and indoor pool discomfort was anecdotal from the user and either dry skin or mild irritation. It's definitely harsh for some people, but not everybody.

 

[newdude]

Forgot to add, never forget you are making people soup. 6 people in 450 gallons is the same as me having 466 and 2/3 people in my 20X40 pool.

I mean. 466 people is one thing. A little cramped. but ok.

But 466.667 people is just plain NASTY.

 

[styopr]

For one, if the tub is ever used in the daytime, the sun will eat 450 Gallons worth of treated tub water in a couple minutes. It wouldn't even matter how high you treated.

If it's an evening only activity as most usually are, then there is no concern.

As far as the evidence goes, me never seeing data doesn't mean it's not out there, but the only thing I've ever seen about hot tub and indoor pool discomfort was anecdotal from the user and either dry skin or mild irritation. It's definitely harsh for some people, but not everybody.

It is outdoors, used during the day, but fully shaded as it is under the deck. Doesn't get any direct sunlight so think I'll keep the CYA out for now. Thanks.

 

[newdude]

Doesn't get any direct sunlight so think I'll keep the CYA out for now.

If it doesn't bother anyone, then have at it with no other concerns.

With any long soaks / afternoon parties, kick everyone out every hour or so to bring it back to SLAM. Say it with me...... People. Soup.

 

[styopr]

If it doesn't bother anyone, then have at it with no other concerns.

With any long soaks / afternoon parties, kick everyone out every hour or so to bring it back to SLAM. Say it with me...... People. Soup.

Oh, believe me, I do! Most of these parties involve kids right now. 6 kids swimming around in there and the chlorine drops quick Close it about every hour or so for 10 minutes to shock and circulate. The nice thing with no CYA It does clear up fast since bringing it back up to about 4ppm (2-3 tablespoons) is way more than shock level. Crystal clear in about 5 minutes with all the jets running - and has two serious pumps running it gets the water churning. PH always seems to drift high (TA maintained 70-80) but I just consider that a fact of life with the jets and air going constantly. Unless???

 

[newdude]

Unless???

Do they make a stenner mini ?

Close it about every hour or so for 10 minutes to shock and

 

[Mdragger88]

The other factor is that some fc really needs to be in the water at all times to prevent person to person transmission of pathogens etc. This means u need to generally start out alot higher than 4ppm with multiple people involved as it gets used up quickly. Having just 20ppm cya allows for the fc to be 8 or 10ppm at the beginning of the party without discomfort yet ensuring you don’t fall below minimum & spread cooties whilst enjoying your tub. The addition of a small amount of cya offers wiggle room.

Also, even though higher fc amounts w/out cya may not bother u - they can be harsh on your equipment & surfaces such as head rests, covers etc. My cya got low (under 20) & I didn’t realize it for a while & I was keeping fc 6-10ppm between soaks. It rusted my ring around my large jet & the underside of my cover became a bit rough instead of supple as it once was. I’ve since started checking cya more often, removed the spot & it hasn’t returned.

 

[styopr]

The other factor is that some fc really needs to be in the water at all times to prevent person to person transmission of pathogens etc. This means u need to generally start out alot higher than 4ppm with multiple people involved as it gets used up quickly.

Thank you. Food for thought, although I have not found through my own observation that the chlorine goes down that much after an hour or so of heavy use. Testing I have always found a minimum amount available and sometimes as much as 2-3ppm. Starting at 4ppm (with 0 CYA) provides, well, 4ppm of buffer. The minimum and target FC for 0 CYA is: .... 0.071 Min ... 0.111 Target. Really negligible amounts. All the rest of that 4ppm as I understand the info in the chart is just reserve (at a shock level). I think I might experiment with some CYA in there to see if we feel the difference! Also the point about a longer reserve (at less of a "charge") might be a worthwhile tradeoff, as is the point about being easier on the equipment.

You've got me wondering, although after thinking about it some, I don't think I'd ever do more than 10ppm CYA with my use case (frequent kid parties) as the requirement to bring it up to "SLAM" level after each party--and maybe even during--seems pretty clear (using the 400 people in the pool analogy). It is just a significant event. 6 kids, rotating in and out, as many as 12 different kids. Goggles on, saliva, you get the picture. Just a huge load.

I think I'd be more comfortable with the 20ppm if it were just like my wife and I or maybe a few friends now and then. I've got some "industrial" situations Though I get it is harder on the equipment.

 

[Mdragger88]

The bigger the tub the less the bather load impact is - so in my little 200 gal tub fc drops pretty quickly w/ a couple dirty humans
The important thing is that u are testing & ensuring u are always maintaining adequate fc levels (which u are) so u are being a responsible hot tub parent
I find that my tub depletes cya fairly regularly so I just automatically use dichlor to shock about once a week or so instead of liquid chlorine after soaking to keep my cya around 20-30. My saltron mini does the rest of the heavy lifting for me.

 

[SchralphMacchio]

It is outdoors, used during the day, but fully shaded as it is under the deck. Doesn't get any direct sunlight so think I'll keep the CYA out for now. Thanks.

Have you ever done a 2 hour FC test with cover open midday? Measure FC at start and end of 2 hour interval with cover open and pumps off? I've been curious about indirect / refracted daylight and whether it can slowly deplete FC.

Our tub is exposed to direct sun and it gets occasional use during daytime hours, so we use CYA.
I'm far from an expert (quite the opposite, a total newb) but I've found Orenda's blogs on the subject to be credible and understandable.
Their punchline is that because CYA will slow down kill times, and because its stabilization benefits drop off dramatically after 15-20 ppm, they recommend keeping it to a minimum. Seems like if you find indirect light is depleting your FC then going to 10-15 PPM CYA and adjusting your FC based on FC/CYA ratios is probably the way to go?

Minimal CYA | Pillar 4

Pillar 4 is Minimal Cyanuric Acid (CYA). CYA (aka Stabilizer or Conditioner) protects free chlorine from sunlight. Some CYA is good, but too much is bad.

blog.orendatech.com

 

[styopr]

.... Seems like if you find indirect light is depleting your FC then going to 10-15 PPM CYA and adjusting your FC based on FC/CYA ratios is probably the way to go?

Minimal CYA | Pillar 4

Pillar 4 is Minimal Cyanuric Acid (CYA). CYA (aka Stabilizer or Conditioner) protects free chlorine from sunlight. Some CYA is good, but too much is bad.

blog.orendatech.com

I have noticed chlorine depletion during the day with no bather load when the cover is off. There is some light that hits the water. I have added a tablespoon of CYA (about 7-10 ppm) and we'll see how that goes! Although I cannot measure it with my test kit (know it's there but it doesn't register)- I can definitely tell the tub holds onto the chlorine more now! We'll see if it is as easy to keep sparkling. So far so good with 3 kids and 1 adult. I did bring it up to 4-5 ppm after to give it a good clean and let it drift down. Might be a good trade-off and have less of corrosive impact on the tub. We'll have to give it the "hot tub party" test 12 kids rotating in shifts of 6, + the random adult.