RO water is very aggressive. Water is the universal solvent and will leach whatever it can.

That said, surely the RO faucet will not be the only cold faucet at the copper sink, right?

The RO faucet will be separate from the house hot and cold faucets and RO water will only be drawn as required for drinking, cooking, or coffee, and hooked to the ice maker right?

Unless you're planning on letting the RO faucet run into the sink constantly I think the copper sink will be OK.

We will have a normal faucet with soft water and then (maybe) an RO faucet. I didn't want to end up having stain type marks in the copper resulting from wherever RO water was standing in the sink, over time.

Oh boy, a copper sink! I hate to burst your balloon, but that is one of the worst choices for sinks. Juices, foods and many other liquids are very acidic and will cause copper to discolor and leach out. How can soak anything in the sink without having to attack it with cleansers afterward or be concerned that copper is coming off?

Even moisture in the air and very mild electrical currents will cause corrosion and bluing.

I bartended for a while with a copper top bar and sink. LOOKED great but what a pain to keep clean. HEY, USE THE COASTER!!! was the sign over the bar. Literally, hours every week were spent on wiping it down and using all kinds of chemicals to keep the boss's baby looking sweet. It was eventually torn out and scraped as soon as the bar was sold.

Your RO water will be the least of your headaces. Sorry, but that is the story of copper fixtures.

Andy Christensen, CWS-II

Andy - good points, but I don't have a bubble to burst :)

I know all about juice and corrosion etc etc. I'm not overly concerned about more or less random stains building up over time. I'm not looking to have a beautiful pristine copper look inside the sink. The difference with those stains is that anytime I have juice in the sink I will be washing it down since I am using the sink (as long as I know the spill is there). With RO water, I might pour a glass of water and have a few drops land in the same spot in the sink and sit there overnight. There was another post about how RO water attacks copper and that you'd have copper ions reentering your water, which is what you are trying to avoid with RO. This reminded me of my copper sink and it made me wonder how aggressive the RO water really is. I wouldn't pour orange juice in the sink and let it sit there overnight. Is RO anything remotely close to a juice in that regard? If not, then you are correct that I shouldn't have any worries.

I have a copper sink with RO water - you won't notice any marks or corrosion from the small amounts of RO water left in the sink.

Thanks alice. That makes sense but when putting something new in a new house it's better to be a little paranoid now than regret it later.

Do you hate your sink as much as andy says you will? :)

I have two copper sinks. One is my prep sink and the other is a trough sink plumbed with only RO water. I ADORE both of them. I also have a copper countertop on my island.

I will caution you - copper changes nearly daily. The sinks have a coating that makes the changes less noticable, but everything you place on copper will cause the color to change a bit. Acids will make a brighter spot, bases will make a darker spot, oils will make a colorful spot (like the look of an oil-slick on water). If you love a surface that varies sublty all the time, you will love copper. If, however, you want your copper to sink to retain that bright, shiny, new copper look all the time, you will hate it - it will be a lot of work to keep it looking that way. My copper has the look of an old penny, exactly the way I want it.

The old penny look is what we want. The front of our sink is a basket weave type pattern that has a patina on it. Of course if we ever want to shine the interior up we can do that.

I can't imagine that copper sinks are at all healthy....

I don't think porcelain would taste very good, either. :)