Chlorine Itch

[RBdwarf]

Hey all, someone on Reddit suggested that I post this here, so here goes:
I've had a hot tub for two winters now and am feeling a little frustrated. I use the tub late Autumn through Spring, about 5 times per week. Last year I had an issue where my legs started to itch, really badly. I put it down to having a kitten who regularly dug her nails into my legs and the fresh wounds being aggravated by the tub chemicals. This year she's a year older and jumps up into my lap without needing to claw her way up, so there are no fresh wounds on my legs. And still my legs itch so bad that I want to scratch the skin off.

I did some Googling and found that the common causes of this are some bacteria that live in hot tubs, or a chemical burn from the chlorine itself. I super shocked the tub to try to kill off anything living in the water, and waited a week while my skin healed (and the chlorine levels dropped back to normal). Last night I went in again. Afterwards I showered and made sure to wash my legs well with soap. After showering I use coconut oil as a moisturiser on my legs. A couple of hours later my legs were itchy again.

What am I missing? I'm fine for almost two months and then it hits. I'm using test strips and they're not showing a high chlorine level. The ph tends towards the low side of normal, should I raise it a little to make the water that little bit more alkaline?

Any group wisdom?

 

[Mdragger88]

Have you ever purged your tub with Ahhsome?
If not - that should be your first step.
It removes biofilms that are resistant to sanitizers alone & that harbor bacteria & pathogens that can cause hot tub rash (pseudomonas folliculitis). A Purge, drain, & refill should be done every 4-6 months.
Often inadequate sanitizer levels (not too much) is to blame for many irritations.
You should always follow the FC/CYA Levels to ensure your tub is sanitary as spas are like people soup. If under sanitized nasties grow quite rapidly.
To maintain your spa you need a proper test kit as the strips are not very accurate - tf100 or Taylor k2006. Test Kits Compared
After you purge, drain, then refill you can follow this guide

How do I use Chlorine in my Spa (or pool)?

If you have a question about any information within this Sticky, please start a new thread for yourself where you will receive very quick responses to your specific questions. Thank you! Introduction There are two main things to consider when maintaining your hot tub water, Water Balance and...

www.troublefreepool.com

 

[RBdwarf]

Have you ever purged your tub with Ahhsome?
If not - that should be your first step.
It removes biofilms that are resistant to sanitizers alone & that harbor bacteria & pathogens that can cause hot tub rash (pseudomonas folliculitis). A Purge, drain, & refill should be done every 4-6 months.
Often inadequate sanitizer levels (not too much) is to blame for many irritations.
You should always follow the FC/CYA Levels to ensure your tub is sanitary as spas are like people soup. If under sanitized nasties grow quite rapidly.
To maintain your spa you need a proper test kit as the strips are not very accurate - tf100 or Taylor k2006. Test Kits Compared
After you purge, drain, then refill you can follow this guide

How do I use Chlorine in my Spa (or pool)?

If you have a question about any information within this Sticky, please start a new thread for yourself where you will receive very quick responses to your specific questions. Thank you! Introduction There are two main things to consider when maintaining your hot tub water, Water Balance and...

www.troublefreepool.com

I purged with Ahhsome last November when I last changed my water.

--
Rob

 

[dan1333]

When you say you super shocked it what does that mean to you? Do you just put in higher levels of liquid chlorine? Dichlor? MPS?

I think MPS is known to cause skin irritation in some people.

As Mdragger mentioned, the problem is often caused by inadequate sanitizer levels so I would question whether or not you have enough free chlorine constantly in the hot tub. To determine this you really need an accurate testing method. The strips border in worthless in my opinion.

I would read the chlorine sticky post at the top of this forum if you haven't already.

 

[Newdude]

What am I missing?

I'm using test strips and they're not showing a high chlorine level.

They also aren't telling you the CYA level which is mondo important to know how much chlorine would sanitize the tub.

0, 20-50- 50-100 and 100-200 does *zero* to narrow it down.

Worse yet, the colors change on the already inaccurate strip. Look away and look back and you'll probably have a slightly different shade.

So people run to the pool store, who get the test simlairily wrong more times than not.

Step 1. Get yourself a reliable test kit to know what's going on in your water. A tf-100 from tftestkits.net or a Taylor K-2006C widely available costs less than a trip to the Dr to fix the rash thay usually only goes away with prescription ointment.

Step 2. Report your levels and we will happily guide you until it all clicks.

 

[ajw22]

Note that chlorine is very harsh if you have 0 CYA.

CYA - Further Reading

www.troublefreepool.com

CYA Chlorine Relationship - Further Reading

www.troublefreepool.com

 

[RBdwarf]

When you say you super shocked it what does that mean to you? Do you just put in higher levels of liquid chlorine? Dichlor? MPS?

I think MPS is known to cause skin irritation in some people.

As Mdragger mentioned, the problem is often caused by inadequate sanitizer levels so I would question whether or not you have enough free chlorine constantly in the hot tub. To determine this you really need an accurate testing method. The strips border in worthless in my opinion.

I would read the chlorine sticky post at the top of this forum if you haven't already.

I used 1L (four cups) of liquid chlorine in a 1500L (400 gallon) tub. That brought down the amount of total chlorine and brought up the level of free chlorine.

 

[RBdwarf]

Note that chlorine is very harsh if you have 0 CYA.

CYA - Further Reading

www.troublefreepool.com

CYA Chlorine Relationship - Further Reading

www.troublefreepool.com

Since our regular chlorine has CYA that's not the issue. In fact, I should probably dump some water and add fresh to bring down the CYA level which is registering as high normal on the strips.

 

[Mdragger88]

To properly shock your tub fc should be at slam level for your cya according to the FC/CYA Levels until your cc’s get below 1.
Your fc (tc-cc) should never go below minimum for your cya lest nasties will grow.
If you don’t know your exact cya level that is almost impossible to do without over/under shooting.

 

[5tan]

To eliminate the itchiness, you need to:

1) Purge with Ahhsome multiple times until no more gunk is released, and don't forget to keep your FC at 10-20ppm during this purge. During the drain, use your garden hose to blast all the jets and drain ports clean of both gunk and of Ahhsome (and open up your drain port even if you use a QuickVac so the gunk building up in the drain channel gets cleaned, chlorinated, and released. Scrub everything with a blue Lysol sponge and a spray bottle or bucket of chlorinated Ahhsome solution.
2) When refilling, maintain 10ppm FC. Also note that the higher the CYA, the less effective chlorine is. If you really want to kill everything (aka sanitize), leave your CYA at 0 and use 10% pool chlorine to hold 10ppm FC for several days (without using the spa), and keep your jets running on low to eliminate chlorine dead spots. After a few days of holding 10ppm FC, then you can be assured everything has been killed off. Then for actual use, you need to build up a 20-30ppm CYA level, so use dichlor tablets or granules to chlorinate until you've added 20-30 CYA. I find that <18ppm CYA makes chlorine harsh and bleaches out swimwear quick. Once you hit your 20-30 CYA, switch back to pool chlorine and never use any solid forms of chlorine until your next drain&fill. Forget your CYA test strips, just use Poolmath to calculate how much CYA you've added and then you never need to think about CYA again until your next fill. If you have tons of splashout, set CYA to 30. Then when you top up, you still have enough CYA, while less than 30, still plenty enough.
3) Ottawa tap water is regulated to 9.0-9.2 pH, and the higher the pH, the less effective chlorine is. Normally you would use dry acid to lower pH, but to rule out sulfate sensitivity, you should use liquid muriatic acid instead of dry acid to lower pH to the 7.2. Most pH strips are difficult to read due to the shades of red/orange they use, and they seem to be inaccurate anyway even if the color matches up to the chart well. Get a Taylor test kit or a digital photometer. Note that the aeration of hot tub jets causes pH to constantly rise, and it rises faster the more TA there is, therefore:
4) After you have your pH down to 7.2, use SpaGuard/BioGuard Optimizer Plus (ensure Plus is in the name), which is 100% boric acid. The older non-Plus formulation increases pH and must be neutralized with acid. Add enough to hit 50ppm borates. The borates makes pH more difficult to change in either direction.
5) NEVER use any non-chlorine shocks, any products containing MPS, any products that partially or fully hides their ingredient list (weekly packets, monthly systems, etc). MPS and its equivalents are HIGHLY, HIGHLY aggravating to those who are sensitive to it. Pretty much everything labelled "non-chlorine" is MPS or something like it, and if any of this stuff gets in your water, you're going to need to drain it.

Ottawa tap water is extremely low in calcium and in TA. To prevent foaming, use calcium hardness increaser to adjust to 180-200. I found that 150 wasn't enough to prevent foaming. Over 200 may run the risk of scaling (mineral precipitation) if you let your pH go high from being inattentive. Do not add TA increaser, it will only cause you headaches (it binds with calcium increaser, making water cloudy and throws off your calculations, it accelerates pH rise via jet aeration, etc). The calcium increaser for pools comes in bigger chunks than the spa calcium increase, but works just the same, and seems to add TA anyway.

You only need to add borates once, enough dichlor once, calcium once, and after that, you should only be adding pool chlorine and acid as needed. Nothing else, not even TA increaser (which is just baking soda).

Never let your FC go below 3ppm EVER, otherwise bad things will grow. This means you may need to add pool chlorine daily or install a SWCG to maintain a baseline level of chlorine. Do not use a floater, any solid forms of chlorine will add CYA. In the absence of an ozonator, biofilms, contaminants, and at a lower temperature (closer to 30C than 40C), a fully sanitized spa on a fresh fill should take 4-7 days to go from 10ppm FC to 5ppm. If the daily FC drop is faster, you have something abnormal consuming your chlorine, probably need to do your Ahhsome purge better.

 

[phonedave]

I used 1L (four cups) of liquid chlorine in a 1500L (400 gallon) tub. That brought down the amount of total chlorine and brought up the level of free chlorine.

4 cups of bleach (or even stronger LC) is a LOT of chlorine to put in a 400 gallon tub.

 

[RBdwarf]

To eliminate the itchiness, you need to:

1) Purge with Ahhsome multiple times until no more gunk is released, and don't forget to keep your FC at 10-20ppm during this purge. During the drain, use your garden hose to blast all the jets and drain ports clean of both gunk and of Ahhsome (and open up your drain port even if you use a QuickVac so the gunk building up in the drain channel gets cleaned, chlorinated, and released. Scrub everything with a blue Lysol sponge and a spray bottle or bucket of chlorinated Ahhsome solution.
2) When refilling, maintain 10ppm FC. Also note that the higher the CYA, the less effective chlorine is. If you really want to kill everything (aka sanitize), leave your CYA at 0 and use 10% pool chlorine to hold 10ppm FC for several days (without using the spa), and keep your jets running on low to eliminate chlorine dead spots. After a few days of holding 10ppm FC, then you can be assured everything has been killed off. Then for actual use, you need to build up a 20-30ppm CYA level, so use dichlor tablets or granules to chlorinate until you've added 20-30 CYA. I find that <18ppm CYA makes chlorine harsh and bleaches out swimwear quick. Once you hit your 20-30 CYA, switch back to pool chlorine and never use any solid forms of chlorine until your next drain&fill. Forget your CYA test strips, just use Poolmath to calculate how much CYA you've added and then you never need to think about CYA again until your next fill. If you have tons of splashout, set CYA to 30. Then when you top up, you still have enough CYA, while less than 30, still plenty enough.
3) Ottawa tap water is regulated to 9.0-9.2 pH, and the higher the pH, the less effective chlorine is. Normally you would use dry acid to lower pH, but to rule out sulfate sensitivity, you should use liquid muriatic acid instead of dry acid to lower pH to the 7.2. Most pH strips are difficult to read due to the shades of red/orange they use, and they seem to be inaccurate anyway even if the color matches up to the chart well. Get a Taylor test kit or a digital photometer. Note that the aeration of hot tub jets causes pH to constantly rise, and it rises faster the more TA there is, therefore:
4) After you have your pH down to 7.2, use SpaGuard/BioGuard Optimizer Plus (ensure Plus is in the name), which is 100% boric acid. The older non-Plus formulation increases pH and must be neutralized with acid. Add enough to hit 50ppm borates. The borates makes pH more difficult to change in either direction.
5) NEVER use any non-chlorine shocks, any products containing MPS, any products that partially or fully hides their ingredient list (weekly packets, monthly systems, etc). MPS and its equivalents are HIGHLY, HIGHLY aggravating to those who are sensitive to it. Pretty much everything labelled "non-chlorine" is MPS or something like it, and if any of this stuff gets in your water, you're going to need to drain it.

Ottawa tap water is extremely low in calcium and in TA. To prevent foaming, use calcium hardness increaser to adjust to 180-200. I found that 150 wasn't enough to prevent foaming. Over 200 may run the risk of scaling (mineral precipitation) if you let your pH go high from being inattentive. Do not add TA increaser, it will only cause you headaches (it binds with calcium increaser, making water cloudy and throws off your calculations, it accelerates pH rise via jet aeration, etc). The calcium increaser for pools comes in bigger chunks than the spa calcium increase, but works just the same, and seems to add TA anyway.

You only need to add borates once, enough dichlor once, calcium once, and after that, you should only be adding pool chlorine and acid as needed. Nothing else, not even TA increaser (which is just baking soda).

Never let your FC go below 3ppm EVER, otherwise bad things will grow. This means you may need to add pool chlorine daily or install a SWCG to maintain a baseline level of chlorine. Do not use a floater, any solid forms of chlorine will add CYA. In the absence of an ozonator, biofilms, contaminants, and at a lower temperature (closer to 30C than 40C), a fully sanitized spa on a fresh fill should take 4-7 days to go from 10ppm FC to 5ppm. If the daily FC drop is faster, you have something abnormal consuming your chlorine, probably need to do your Ahhsome purge better.

Wow, thanks! Lots to digest in there!

--
Rob

 

[Eauclaire]

Very thorough post 5tan, sent it to my spa-owner friends in Ottawa.

 

[greatestvalue]

@5tan -
Thank you so much for sharing this info. For those of us who are new and old to spa living this is great to know.
So what do you do if your owners manual says use MPS weekly.
"WEEKLY SHOCK:
Using a potassium monopersulfate (MPS) shock, add approximately 2 oz (60 ml) into the filter bucket
while the jets are running. Shocking is achieved by adding the MPS to turbulent water. Leave the cover
up and jets on high for 10 minutes. Then shut jets off and return the cover to the closed position to
maintain heat."

 

[Mdragger88]

@5tan -
Thank you so much for sharing this info. For those of us who are new and old to spa living this is great to know.
So what do you do if your owners manual says use MPS weekly.
"WEEKLY SHOCK:
Using a potassium monopersulfate (MPS) shock, add approximately 2 oz (60 ml) into the filter bucket
while the jets are running. Shocking is achieved by adding the MPS to turbulent water. Leave the cover
up and jets on high for 10 minutes. Then shut jets off and return the cover to the closed position to
maintain heat."

Mps is not recommended- it can be an irritant for many & can also read as cc’s if interference regeant is not used, making it complicated if your goal is reducing cc’s.
It is also only an oxidizer. Chlorine however is both an oxidizer & a sanitizer. Routine blind “shocking” on some set schedule whether your tub needs it or not is not what TFP recommends. TFPC is based on giving your tub/pool what it needs based on your testing. No more, no less.
Many who manually chlorinate their spas find they need to raise fc above high target to near slam/shock level for their cya FC/CYA Levels after use to account for current bather waste after a soak & still allow their fc level to remain above min for their cya until their next use/dose the following day.

 

[5tan]

By understanding why that manufacturer wrote that in the owner's manual and by understanding the mechanisms of action of non-chlorine shock (usually MPS), you can safely ignore the requirement to use MPS. That manufacturer may not be aware of, or doesn't care about, people with skin sensitivities. MPS and similar compounds are highly irritating to those who are sensitive to it - the easiest way to find and confirm such information in research publications is to search for the word "persulfate" under the topic of dermatology in any university's academic journal searching system. You'll see it's much more common that spa manufacturers and spa chemical manufacturers realize, who aren't exactly in the business of dermatology.

You can do a shock (i.e. clear out Combined Chlorine) via the addition of sodium hypochlorite aka pool chlorinating liquid aka unadulterated bleach, in accordance with breakpoint chlorination calculations, which basically is to keep adding bleach until the numbers level out. I consolidated some information on the topic of shocking and breakpoint chlorination a few months ago, see How to shock a chlorine spa, Understanding Breakpoint Chlorination, Breakpoint Chlorination