What is the ph of rain ?

[TomAtlanta]

What is the ph of rain ?

Other related questions:
My pool ph is a little high, about 7.9 - 8.0. Will it gradually go up or down over the winter as rain water is added to it?
I just tested my tap water and it has a very high. Is this normal?

 

[UnderWaterVanya]

What is the ph of rain ?

Other related questions:
My pool ph is a little high, about 7.9 - 8.0. Will it gradually go up or down over the winter as rain water is added to it?
I just tested my tap water and it has a very high. Is this normal?

Tap water pH in my area is above 8. This is intentional per the water department in order to reduce corrosion.

 

[dmanb2b]

I'm extra lucky...in addition to high PH my TA is 330+. It all depends. Post up a set of results, before closing....ph near 8 is too high IMO to rely on acidic rain to do the lowering...even if the rain is slightly acidic, rain aerates your water as well which raises PH. Typical showers tend to be a neutral PH event.

 

[TomAtlanta]

Post up a set of results,

Will do in a few days. I haven't done a total test in a while, but will do it and post before this weekend.

 

[chem geek]

The pH of rain is generally acidic due to the dissolved carbon dioxide (carbonic acid) from the air as well as from other acidic sources (nitric and sulfuric acids). However, the TA (pH buffering) of rain is fairly low so the effect of rain on pool pH is minimal from the rain itself (unless it is very, very acidic). Generally, rain increases aeration of the pool water so will raise the pH of the water as a result.

If you dilute the pool with a lot of rain water, but don't have it splash into the pool, then the pH will likely drop slowly. If you let the raindrops splash into the pool, then the pH may go up at first and then slowly drop if there is enough dilution of the water.

 

[imrodee]

@chem - You explain things so clearly... that I even get it.

Thanks for that.
Helen

 

[Just-a-PB]

Courtesy of Wikipedia,

The pH of rain varies, especially due to its origin. On Americas East Coast, rain that is derived from the Atlantic Ocean typically has a pH of 5.0-5.6; rain that comes across the continental from the west has a pH of 3.8-4.8; and local thunderstorms can have a pH as low as 2.0.[70] Rain becomes acidic primarily due to the presence of two strong acids, sulfuric acid (H2SO4) and nitric acid (HNO3). Sulfuric acid is derived from natural sources such as volcanoes, and wetlands (sulfate reducing bacteria); and anthropogenic sources such as the combustion of fossil fuels, and mining where H2S is present. Nitric acid is produced by natural sources such as lightning, soil bacteria, and natural fires; while also produced anthropogenically by the combustion of fossil fuels and from power plants. In the past 20 years the concentrations of nitric and sulfuric acid has decreased in presence of rainwater, which may be due to the significant increase in ammonium (most likely as ammonia from livestock production), which acts as a buffer in acid rain and raising the pH.[71]

70 Joan D. Willey (1988-01). "Effect of storm type on rainwater composition in southeastern North Carolina". Environmental Science & Technology.
71 Joan D. Willey (2006-08-19). "Changing Chemical Composition of Precipitation in Wilmington, North Carolina, U.S.A.: Implications for the Continental U.S.A". Environmental Science & Technology.