Printable View
For the first time in over twenty years (because I normally wear contacts) I recently swam for an extended period with my eyes open underwater. After this my eyes were significantly irritated and bloodshot. I don't know why this would happen; I had recently tested the water to have a 0 CC (as always) and about a 7.5 pH.
Any ideas?
Don't know why. PH of 7.5 is good. Maybe just prolonged time in the water.
Even with ideal pH of 7.5 (see this link) and no chloramines, your eyes are going to get irritated if you keep them open in water that isn't high in TDS. Human tears have around 9000 ppm so a standard pool with 500-1500 ppm is likely going to give you a problem. Even saltwater chlorine generator (SWCG) pools with 3000 ppm salt will still cause pressure and swelling in the eye, though it will take longer. One would need to get near 7000 ppm TDS before one eliminates the problem (see this paper).
The problem is due to osmotic pressure since the water in the pool is more concentrated than in your eye (the extra salt in your bodily fluids makes the water less concentrated) so water enters into your eye until the pressure in the eye builds up to equal this osmotic pressure. Over time, this pressure irritates the eye. Note that this issue has nothing to do with chlorine -- having your eyes under pure water would cause the same problem, probably even faster.
Richard
Additionally, IIRC, the pH of the eye is closer to 7.3. As Richard stated, a lack of salinity is probably more the cause than anything else, given everything else is in line.
I'm constantly amazed by the info I find here on the forum! Thanks for answering this... I've had the same question for a while...
How do you increase the TDS if it is low? I have a vinyl pool and have always ignored TDS.
Add salt.
Many pool owners add enough to reach around 2000 ppm and report a increase in bather comfort. There has been discussion about this in the past on the forum and on other forums and I don't remember anyone ever regretting adding salt.
Can you post the rest of your readings, like CYA and FC for starters?
Attaching Chem_Geek's papers:
Effect of saline on the eye irritation caused by swimming-pool water, 1973
Fluorophotometric measurement of pH of human tears in vivo, 1997
http://www.ncbi.nlm.nih.gov/pubmed/9154387
Ben
That's 2000 ppm of salt, not a TDS reading?Quote:
Add salt.
Many pool owners add enough to reach around 2000 ppm and report a increase in bather comfort.
Apologies if I am re-treading old ground. When I search for TDS, it's to short to be used by the search function.
That's correct.Quote:
Originally Posted by Spensar
In practice, TDS and salt at such higher levels will be very close -- usually the TDS is around 200 ppm higher than the salt level, but this depends a lot on how TDS is measured and usually it isn't measured accurately (since you have to know the components of the water to properly calculate TDS in ppm). So just use a decent salt test and calculate the amount to add based on salt ppm (you can use The Pool Calculator for that).