We're putting in an R/O under the sink - with pressure tank - and will tee the output to both our Instant-Hot and to the fridge water & ice - no extra faucet on the sink. My thinking was that since we are only going to drink cold water (and ice), why bother with another thing on the sink. It took me weeks to research and find a system that would do this - with enough pressure to work w/the fridge. I'll update when it gets installed. My under sink is going to end up looking like a nuclear power plant with the R/O, tank, hot water, disposal ... ! Luckily we're storing cleaning supplies elsewhere, as there won't be much room left!

astridh -- my husband is better suited to answering your question but from what I remember him telling me: RO water is not just corrosive to the tank / pipes / tube (I think he said "tank" but I'm including it all in case I've forgotten) in an insta-hot, it is dangerous to the drinker. (it's dangerous because what the RO water corrodes is carried through the water supply to your cup of tea) He really wanted RO water and I really wanted just one faucet. So, we're going with just one faucet that does insta-hot AND filtered water. We've decided to live with it a while and see if the filtered water is good enough. If it is, great. If it's not, then I guess we'll either have to reassess (and get another faucet) or be prepared to frequently replace the insta-hot tank. I wish I had more details for you -- when I talk with him later I'll ask to see what pertinent info I left out. I found a panoply of great-looking faucets -- Brasstech and Little Gourmet (Mountain Plumbing) both have a slew of styles and finishes. (We purchased a Little Gourmet faucet and insta-hot tank -- I think it's a Culligan filtered water system?)

Found good info and thought i would paste here. The i have a continues TDS on my RO input and output and my output is currently around 40 PPM. The Output feeds my Ice-maker and my Instant hot through copper pipes.... I was worried about corrosion and possible leaks and the below paste makes me feel better! Question: Will putting a whole-house reverse osmosis (RO) system on a house with copper pipe cause leaks? aquacareservice@embarqmail.com Answer: Will putting a whole-house reverse osmosis (RO) system on a house with copper pipe cause leaks? aquacareservice@embarqmail.com The simple answer to your question is yes. Copper plumbing that is exposed to RO water will cause pitting; however, the question begs for a more thorough explanation of whole-house RO. To begin with, when most people hear the term RO, they think of water that has had the mineral salts reduced by 99 percent. While this is good for life support water, this is not practical for domestic,whole-house, working water. It is good to keep in mind that the water for this type of application should have a finish TDS of 50-100 ppm. The product water off the membrane should pass through a small column of calcite or equivalent product, or it can be treated with soda ash to neutralize the acidic nature of the water to a less corrosive state. Bear in mind that these products must meet the NSF standard for food service. In addition to neutralizing the acid, calcite will add calcium carbonate to the water. If the water being treated by the RO still contains hardness, then an acid feed is generally needed to drop the pH to increase the solubility of the hardness. This will allow the membrane to reject high levels of hardness while preventing scaling. Therefore, passing the water through a softener to remove any remaining hardness is a very efficient way to provide the kind of working water that most homeowners would like in the first place. Gary Battenberg, Technical Director, Hague Quality Water International As a rule of thumb, if the TDS (total dissolved solids) concentration of the RO water is above 10 ppm (almost all is >10), it should not be aggressive enough to dissolve copper and cause leaks.

Your missing part is a FLOW RESTRICTOR and should be replaced when ever the membrane is replaced. It regulates the water flow to drain, not air. If the old one is still in there you can remove the old one and clean it carefully... it clogs with debris. The shut-off valve pictured above is exactly that... a shut-off valve. It installs in the tubing that supplies water to the RO so you can sht-off the water going to the RO in case you need to service the RO... as you do now. If the tubing that supplies water to the RO is 1/4" PE then you need a 1/4" shut-off valve. If the tubing that supplies water to the RO is 3/8" PE tubing then you need a 3/8" shut-off valve. Home Depot carries them. Also. mind what I said about a saddle valve. If the line supplying water to the RO is hooked up with a saddle valve REPLACE it with a conventional connection. Saddle valves will leak sooner or later and are a giant water leak waiting to happen. If any of this confuses you, then get help. This is important.