what does High/Low Ph do to your skin?

rsharp

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Jun 12, 2010
129
just curious to know if a high or low ph will have any effect on our skin...
 

JasonLion

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Yes and no. {EDIT}PH anywhere remotely near the normal range won't do much of anything, but really extreme PH values from straight chemicals before they are added to the water can have some dramatic effects. The rest of this talks about really extreme PH levels (for example straight muriatic acid or lye).{/EDIT} As long as you don't have any cuts nothing obvious will happen right away, but really extreme PH will cause itching. Getting really extreme PH in your eyes can blind you almost instantly, getting in on cuts can be painful, and getting it on mucus membranes can be extremely painful and likely to cause injuries.
 

anonapersona

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Nov 5, 2008
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Jason, how high or low are we talking about to get itchy skin? I assume the other reactions would take even more extreme values.
 

rsharp

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Jun 12, 2010
129
my ph is at 7.2.. im pretty sure this wouldnt cause any skin problems. no one has ever said anything!!!
 

chem geek

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Mar 28, 2007
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The pH of human skin is normally acidic at a pH of around 5.4 to 5.9 (see this link and this link) so having the pool be unusually acidic isn't likely to cause a problem to skin unless it's much more acidic, such as in pools that use Trichlor without adjustment that get down to a pH of 4.5 or lower (i.e. they immediately show red on the TA test). Generally, it takes a fairly low pH below 3 to cause itching -- lemon juice is around a pH of 2.3 and if put on your skin and left to dry you will probably find that it itches.

Alkaline soap has a pH around 9-10 but can feel slippery on skin rinsed in soft water as some of the soap remains on the skin. If the pH is higher, such as found with lye (13 or higher) or undiluted bleach (11.9 or higher) or chlorinating liquid (12.5 or higher), the oils in your skin saponify which basically turns fats and oils in your skin to soap which is why it feels slippery.

So generally speaking, a pH range of 7 to 8 isn't going to do very much with your skin unless you have very unusual sensitivities. Tap water is usually in the pH range of 7.5 to 8.0 and is intentionally made more alkaline than neutral in order to reduce metal corrosion.

Your eyes, on the other hand, are more sensitive to pH changes in the water, but still not that sensitive at least to pH. The pH of human tears varies somewhat but averages 7.5 (see this link while this one says the average is 7.0[END-EDIT]). This paper talks about various factors affecting eye irritation in swimming pools. The primary factor for irritation appeared to be osmotic pressure since adding salt to the water at around 0.5% (around 5000 ppm) in the field study or 0.7% (around 7000 ppm) in the lab study virtually eliminated the irritation which isn't much of a surprise since the salinity of human tears is around 9000 ppm. The pH varying from 7 to 9 did not show a significant difference in irritation. This link describes how the chloramines can be more irritating. Other studies show that nitrogen trichloride (see this link among many others) can be particularly irritating.

When there is no CYA in the water, then the production of volatile and irritating nitrogen trichloride is much more prevalent, especially with higher bather (or other organic) loads. Also, it is very dependent on the pH where far more is produced at lower pH (from a pH of 8.0 to 7.0 and with no CYA the amount of nitrogen trichloride increases by a factor of 4.3 whereas the active chlorine level increased by a factor of 3.4). So I strongly suspect that the main correlation with eye irritation as well as "bad pool chlorine" smell, coughing and other problems is mostly associated with nitrogen trichloride and that at lower pH more is produced. It isn't the pH of the water itself that is the problem, but rather the effects on the chemistry of what is produced at the lower pH. In pools with CYA in the water, especially in residential pools that typically have low bather load, I suspect that preventing moderate changes in the pH are more important for protection of plaster surfaces and to prevent metal corrosion than for prevention of irritation of the human body.

Richard
 

JasonLion

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I edited my post above to make it clear that I was talking about really extreme PH levels, not something you should ever experience in the bulk pool water.

For more realistic pool PH levels, PH below 7.2 causes many people to feel some rather mild stinging of their eyes and PH in the low 6s or lower can result in some skin itching and somewhat worse stinging of your eyes.

Sorry for any confusion.
 

rsharp

Well-known member
Jun 12, 2010
129
well thats good to know. i try to keep my ph around 7.2 b/c of a stain problem ive had... thanks for the info everyone!
 

astrolite

Active member
Jun 25, 2008
31
Lewisberry, PA
Just a little anecdotal evidence, my pool maintained within the proper PH range has no effect on my eyes. However, my well water is off the scale yellow on the PH test, very acidic and stings when I get it in my eyes.
 

porkandbeans

Active member
Jun 6, 2013
42
SoCal
I'm going to bump this old thread only because I found it such an interesting read - thanks for the info!
I usually use acid to lower my pH to around 7.2-7.4 and it creeps up on me. I was away and now my water is 8.2 and I forgot to pick up more acid so I'm all out. It is 104 degrees out so eff it, I'm in anyways. The 8.2 water feels fine and I'll normalize the it back to typical levels tonight. No discomfort so far. I'll report back if I feel any different later.
 

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