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Name: Mythali
Status: Student
Grade: 9-12
Location: N/A
Country: South Africa
Date: Summer 2009

Is rain water considered as hard water or soft water? Can anyone drink the rain water if its not an acid rain?

Rainwater is soft water. Water is made "hard" by dissolved calcium or magnesium ions, neither of which are present in rain water (at least, not until it runs over calcium- - or magnesium- containing compounds on the Earth's surface).

Richard E. Barrans Jr., Ph.D., M.Ed.
Department of Physics and Astronomy
University of Wyoming


The Ask-A-Scientist archives includes information on drinking rain water - usually it is safe to drink rainwater.

Even rainwater in pristine areas not affected by air pollution is slightly acidic. That does not mean that you cannot drink it.

Rainwater is usually "soft". The definition of "hard" water is water that contains a large amount of minerals, particularly calcium, magnesium, and iron.

Minerals get into ground water as it passes through the soil and the bedrock or "hardpan" gravel below the soil. Most wells contain "hard" water. Most lakes have fairly soft water unless they are fed primarily by springs from the ground.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory

I would not want to make a general statement, but rain is the product of the condensation of water vapor into liquid water. So it "should be" relatively pure. But to say that anyone can drink rain water would be overstepping the bounds of possibilities.

Vince Calder

Hi Mythali

Rain water is soft water. Other people may have other ideas, but I believe you can drink any rain water. Acid rain just does not have enough acid or other pollutants in it to hurt you. But I would not drink any water out of any streams or rivers.

A common way of purifying water is to boil it to steam then condense the steam back to liquid in a separate vessel. That process is called distilling and it leaves most of the impurities that were in the water behind. It is a common way of converting salty sea water to fresh water.

Rain is just earth surface water that has evaporated (turned to vapor) into the air, then recondensed as water in the clouds in rain drops. When the rain drops get heavy enough to resist the windy updrafts in the clouds, it falls to earth's surface in the form of rain, or sleet, or hail, or snow if it is cold enough.

So rain forms by the same process as the distilling process and is pure enough to drink.

Hard water has dissolved minerals in it that are left behind in the pot after you convert the water to steam.

Mike Stewart

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