Cya In A 400 Gallon Spa

[104 Degrees]

What should the number be?? or my tub just tested at 82 ppm and its been 3 months since the water has been changed.

Thanks john 104 degrees

[tony]

What should the number be?? or my tub just tested at 82 ppm and its been 3 months since the water has been changed.

Thanks john 104 degrees

You really don't need any CYA in a spa that has a cover. You just have to guard against very high levels. 82 ppm is not too bad and normal for water three months old and sanitized with dichlor. In an outdoor pool, you want CYA levels to be about 30-50 ppm to protect chlorine from the sun which will eradicate it. The problem with CYA is it inhibits chlorine from sanitizing. The higher the CYA levels, the higher free chlorine level is needed to get the same kill rate. You should be changing your water within a month so you should be fine.

[chem geek]

See this post I just made. For most bacteria, I would agree that you don't need to worry about the buildup of CYA, but for the bacteria that causes hot tub itch, Pseudomonas aeruginosa, that is another matter. Most people are not sensitive to this bacteria (unless the skin has a cut or sore), so it's a small risk to take.

Richard

[104 Degrees]

What should the number be?? or my tub just tested at 82 ppm and its been 3 months since the water has been changed.

Thanks john 104 degrees

You really don't need any CYA in a spa that has a cover. You just have to guard against very high levels. 82 ppm is not too bad and normal for water three months old and sanitized with dichlor. In an outdoor pool, you want CYA levels to be about 30-50 ppm to protect chlorine from the sun which will eradicate it. The problem with CYA is it inhibits chlorine from sanitizing. The higher the CYA levels, the higher free chlorine level is needed to get the same kill rate. You should be changing your water within a month so you should be fine.

Thanks tony

I have not been using the tub because of summer. i think if i have been using it like in winter i would have the itch. or would of had it a month ago.

john

[104 Degrees]

See this post I just made. For most bacteria, I would agree that you don't need to worry about the buildup of CYA, but for the bacteria that causes hot tub itch, Pseudomonas aeruginosa, that is another matter. Most people are not sensitive to this bacteria (unless the skin has a cut or sore), so it's a small risk to take.

Richard

Richard i'm glad your here. What should the level be for CYA---20?? If so i'm going to dump the spa and go with what you recommended---Bleach.is the vermonter recomending liquid bleach to??

Thanks John

[chem geek]

John,

Unfortunately, there is only one source that gives CT values for the bacteria that causes hot tub itch, but based on those values (30-50 for 99.99% kill compared to E.coli of 0.04 for 99% kill and most heterotrophic bacteria of 0.08 for 99% kill), I came up with 4 ppm FC at 20 ppm CYA as being a conservatively safe level to go with (you can read technical details about that here). That usually works out to 1-2 weeks of Dichlor usage and then switching to unscented bleach and maintaining a 4 ppm FC level (approximately).

The Vermont Method guy (Brad) was never "official" in terms of proposing a method. It's one of those things that someone says and then it takes off. We haven't come to a conclusion yet as he's reviewing links I sent to him (as he pointed out, they refer to other links so it can get quite involved), but he does understand my point. I would say he's not in disagreement, but we haven't come to a mutual "well, what do we do" yet. I'm probably being too conservative with the low 20 ppm CYA level while using Dichlor alone is taking a small risk after 1-2 months. I don't think we're going to come up with anything definitive unless scientific studies are done so you'll just have to take this as information and do with it what you will.

Richard

[104 Degrees]

John,

Unfortunately, there is only one source that gives CT values for the bacteria that causes hot tub itch, but based on those values (30-50 for 99.99% kill compared to E.coli of 0.04 for 99% kill and most heterotrophic bacteria of 0.08 for 99% kill), I came up with 4 ppm FC at 20 ppm CYA as being a conservatively safe level to go with. That usually works out to 1-2 weeks of Dichlor usage and then switching to unscented bleach and maintaining a 4 ppm FC level (approximately).

The Vermont Method guy (Brad) was never "official" in terms of proposing a method. It's one of those things that someone says and then it takes off. We haven't come to a conclusion yet as he's reviewing links I sent to him (as he pointed out, they refer to other links so it can get quite involved), but he does understand my point. I would say he's not in disagreement, but we haven't come to a mutual "well, what do we do" yet. I'm probably being too conservative with the low 20 ppm CYA level while using Dichlor alone is taking a small risk after 1-2 months. I don't think we're going to come up with anything definitive unless scientific studies are done so you'll just have to take this as information and do with it what you will.

Richard

I'm going to try the liquid bleach sytem that you have given me. can i still use my silver or "nature 2 cartrage" with the bleach ?? I always get a rash on my lower right side of my belly and my left side of my ankle. the spa store three months ago said i have a reaction to the shock, they had me at three Tablespoons weekly plus my clorine at 4ppm.

Since then i have used one Tablespoon of shock and have had the clorine at one or two ppm.

The only problem is i dont use the tub but once a week maybe in the summer. i have not icthed since i went with the lower shock and clorine levels.

She told me that the rash the one the High CYA will cause or let grow would be all over my body not just in the same place or the two places its been on me.

Do you agree on the rash being on your whole body or will the rash just hit certain areas??

John

John

[chem geek]

Though allergic reactions to almost anything are possible, I am suspicious about the shock. Was this non-chlorine shock, potassium monopersulfate (MPS)? Or was it Dichlor powder? And what was your source of chlorine -- Dichlor?

I have never heard of high CYA causing a rash. It's possible that the high non-chlorine shock (MPS) levels caused irritation. It is an oxidizer, but I don't know how it reacts to skin specifically. I don't know what would cause a rash in one place vs. all over. Usually for hot tub itch (from what I've read and has been reported), the rash usually occurs where there is a skin irritation already there, such as a cut, bruise, sore, thin skin, etc.

Test the current CYA level in the spa and if it's high, consider doing a drain/refill to start over or to lower the CYA level. Once the CYA level hits 20 ppm or so, switch to using unscented bleach.

Then again, there's the motto "if it ain't broke, don't fix it" so if using less shock has you in good shape, that's what is most important.

[104 Degrees]

Though allergic reactions to almost anything are possible, I am suspicious about the shock. Was this non-chlorine shock, potassium monopersulfate (MPS)? Or was it Dichlor powder? And what was your source of chlorine -- Dichlor?

Then again, there's the motto "if it ain't broke, don't fix it" so if using less shock has you in good shape, that's what is most important.

Richard

Its hot tub and spa shock with the active ingrgredient persulfate compound. chlorine source Dichlor.

Thanks John