Copper Pipes for Reverse Osmosis

I have one up question.Why does the RO water “dissolve” the copper piping?I thought that RO water was really “only” ultra filtered water (i.e. water that has passed through a permeable film leaving behind undesirables) and as such the chemical composition should not have changed.

I can only wonder what it would do to your stomach if it “dissolves” copper!

Thanks for your comprehensive reply.

From Cornell University site (PDF file is here):
The storage tank, tubing, and dispensing faucet should be made of plastic, stainless steel, or other nontoxic materials. The low pH and mineral content of RO-treated water may corrode copper pipes and allow lead to leach into the drinking water from brass components.

Further explanation: Most brands of Reverse Osmosis Water Purification systems would reduce at least 85% to 90% of salts found in water. Therefore, one may assume the salts concentration would be about one ninth of the content in the feed water.

The aggressiveness of this RO purified water towards the holding materials into which it comes in contact, is a function of its purity.

The better and finer the purity of the water, the more its aggressiveness.

Since RO pure water is very aggressive, if ran through a copper pipe it will pick up a copper taste. The tubing after a reverse osmosis unit should therefore be non-metallic. RO units will pass all the CO2 that is found in the feedwater.

This means the purified water will be more corrosive.

With all this stated, don’t use copper pipes after any (brand of) Reverse Osmosis Water Purification system.

PS. Well, I didn’t hear of anyone complaining their stomach was dissolved due to RO water…

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