does reverse osmosis & ph?

[xxxrazor]

Does reverse osmosis water machines affect ph up or down? I live on the west coast of Canada and our tap water has a ph 6.6....just wondering if reverse osmosis machine can correct this naturally.

[Warnberg]

Yes, typically RO water will have a pH of 6.0

From another website:
"Why is the pH of my RO water so low?
If you measure the pH of reverse osmosis (RO), or any other type of purified water, you will typically find that the pH reads around 6. This might seem like a problem to be adding something with such a low pH to a reef aquarium, but this is not an issue.

pH measurements of pure water mean very little, as all it takes is a very small impurity or additive to make a large difference in the value. The most influencial thing is carbon dioxide from the air, which adjusts the pH to in the region of 6 if left for long enough and allowed to reach equilibrium. The reason that it only takes a small additive to change the pH is the pure water has an extremely low alkalinity (which is a measure of how well the water will resist a pH change). Therefore, the lower the alkalinity the easier it is to change the pH. You can read up more on alkalinity in this Alkalinity article. http://ozreef.org/library/articles/alkalinity.html

As for if this low pH water is actually a concern when adding it to your reef aquarium, no it is not. It will not adversely effect your tank water since the alkalinity is so low and will not change the pH of the reef aquarium's water."

[sasquatch]

Now thats a coincedence last night(elsewhere) I read a post on extremely high ph when changing filters on ro/di, cant verify truth of this or think of a reasonwhy.Steve