chlorine concentrations

[Chris73]

Hi there,

Does anybody know about a table with chlorine concentrations in water (swim pool) and impacts on humans? Normal, max. allowed ... lethal...? Something down that line? Thanks!

 

[orenda1168]

Chris73:

I am not aware of such a table, but offer the following guidelines for free chlorine levels in both commercial and residential pools:

Minimum concentration to effect sanitizing: 0.5 ppm in both systems.

Typical concentration: 1.0-3.0 ppm in residential pools, 2.0-5.0 ppm in commercial pools.

Maximum concentration generally permitted/desired: 10.0 ppm in both systems, excluding superchlorination periods for organic/chloramine removal which can go to about 20 ppm (pools closed to swimming during these periods).

I do not know what the lethal concentration of free chlorine in water is, but presume it is far in excess of the levels shown above.

In general, and unless a bather has an allergenic reaction to free chlorine, there is little impact on humans within the typical use concentrations. Conversely, combined chlorine (chloramine(s)) at relatively low concentrations in the neighborhood of 0.1 - 0.2 ppm or more can and do irritate sensitive skin/membrane areas, and do have a distinctive "chlorine" odor that is not otherwise present at typical free chlorine concentrations.

Orenda

 

[hydrae]

EPA limit for drinking water is 4.0 mg/l (water to be consumed)
Hydrae

 

[orenda1168]

Hydrae:

EPA drinking water standards for chlorine are not applicable (maybe better stated as not applied or enforced) to recreational waters on the presumption that such waters will not be routinely ingested.

Orenda

 

[hydrae]

Orenda

Since Chris was looking for a variety of information about effects and concentration, and to find that someplace official, I was providing a hard number that is considered safe for all domestic uses including ingestion as determined by a branch of the US government that is concerned with human safety, and that Chris can use as a conservative figure, if the level is below 4 ppm it is safe to drink, bath, shower, and cook then it is reasonable to assume it is also safe to swim in. While it might be safe to swim in a concentration higher than 4, I would not want to...

As for chloramines; di-chloramine and tri-chloramine are odorous at very low levels and have the affect you describe. Mono-chloramine does not exhibit those same properties, but getting just mono-chloramine in a swimming pool would be a difficult balance and not worth the effort. Not all chloramines are bad.
Hydrae

 

[orenda1168]

Hydrae:

Not to beat this horse to death, but it is a fact that numerous commercial pools (and you can put this number into the thousands), not to mention residential types, run a free chlorine level at or above 4 ppm as their version of "more is better". I don't support this as it is a waste of chlorine in most cases (though some elevated temperature therapy pools may be the exception) and probably aggravates chloramine formation, but the waters are safe to swim in.

I do disagree that monochloramines are not a problem, particularly in well-used commercial pools. These are easily formed by hypochlorus acid reactions with such things as urine, and are a (maybe the)prime cause of eye and skin irritation. Di- and tri-chloramines are also routinely present, causing the same problems, and are much more difficult to break than monochloramines by either break-point chlorination or non-chlorine oxidizing chemistries.

Orenda