Hot tub and coughing

[deenamccauley]

I'm really not sure what I am doing wrong here but for some reason this year when the jets run in our hot tub it causes everyone to cough.
Although my numbers aren't perfect they don't seem to be that far off.
Any one have any ideas on what I am doing wrong? And how to fix this?

Latest numbers
FC 4.00
CC .4
PH 8 (this is always on the high side)
Alk 60

The only thing different we did this year was add salt. I'm not sure of the level but I know it is not that high.

2000 litre fiberglass hot tub.
Using 12% chlorine, BBB

 

[gregg123]

In the business I am in we work occasionally with muratic acid and I know if you get a whiff of the fumes it will make you cough. I see you have a muratic acid auto feeder. Might check to see how close this is to the spa and if the fumes are near people. Good luck.

 

[JasonLion]

CC is often a respiratory irritant, which will tend to get into the air more rapidly when the jets are on. You never want to have more than one drop to clear the CC reading. Since you appear to be doing the CC test by 0.2s, your CC level of 0.4 is too high. If you are doing the CC test by 0.5s then up to 0.5 is alright.

 

[deenamccauley]

I should have been more clear. The hot tub is in our home, where as the pool is in a whole other area/building, so I do not have auto feed on the hot tub.
The CC makes sense as I always seem to have some in the hot tub. Now that you mention it I know last year we started adding MPS to stay on top of this. With a 2000 litre hot tub how much MPS would you advise? Every day, every other day?
That's the only problem with only running the hot tub for the winter months, I swear I forget everything I learned from the year before.
One other question, I know I've read on there that some recommend that you use some stabalized chlorine to have at least a low level of CYA in the hot tub. Is that accurate for an indoor hot tub as well?
Thanks for your help.

 

[chem geek]

The most common problem hot tub users have is not using enough chlorine (or other oxidizer such as MPS) in their hot tubs to oxidize all of the ammonia/urea from sweat/urine. This can lead to a buildup of monochloramine which can smell and irritate. The rough rule of thumb is to have 7 ppm FC in 350 gallons for every person-hour of soaking. That's 3.5 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of MPS non-chlorine shock, all independent of spa water volume.

The other problem could be using unstabilized chlorine (i.e. bleach) without first using Dichlor. You should have some CYA in the tub and using Dichlor for a week is the easiest way to do that to get to around 20 ppm CYA and then switch to bleach until your next water replacement (usually around 3 months). If you use only Dichlor, then after a month or two the CYA level will be high and can slow down getting rid of ammonia fast enough and can be less effective sanitizing against the bacteria that causes hot tub itch.

Richard

 

[deenamccauley]

I have not used any Dichlor so I will start to do that for the next week. I have been using straight 12% bleach.
I think you are right on with my not keeping the chlorine levels high enough,despite my keeping them at 3-4, that just was not enough. I brought them up to 10 for 3 days and I'd say it's 99 % improved as far as the coughing goes.
I will keep my levels higher from now on.

Thanks everyone for your help.

 

[chem geek]

If you only use bleach and never used Dichlor or otherwise had CYA in the water, then the active chlorine level in the hot tub was WAY too strong. This not only degrades hot tub components much faster as well as your swimsuits and skin, but the chlorine will outgas much faster and will have the FC level drop too quickly. Using some, but not too much, CYA in the water (such as using Dichlor for a week and then switching to bleach) will help maintain a more consistent but much lower active chlorine level. Using enough chlorine will eliminate the chloramines that are probably forming from your sweat and that should reduce the smell.

Some people find it hard to soak with a higher FC in the water as they don't want any odor at all. A less than ideally sanitary way to do this is to add chlorine after your soak such that you have a small amount of measurable FC the next time you start to soak -- say, around 1 ppm FC. This won't be enough to get rid of your bather waste during your soak, but will limit the amount of chloramine smell. If you then add bleach after you get out, then that will form and then oxidize chloramines (keep the cover off for an hour after you soak). There is a small risk of not having any FC during part of your soak, but that's the tradeoff between not having any smell vs. maximum sanitation. The risk is that some bacteria will stick to surfaces and start to form biofilms, but by adding a lot of chlorine after the soak this risk is lessened (though not as low as having sufficient FC at all times). It's a low risk especially since you generally don't soak for very long (usually a half-hour or less).

Richard