RO water is what is often called "aggressive". Basically, most of the contaminants (total dissolved solids = TDS) have been removed. That means this water is looking for ions to appropriate. It can find them in metal lines. The only thing worse than RO water this way is distilled water which has Zero ppm dissolved solids. (RO water is typically 5-10ppm which is still "aggressive") Distilled water is incredibly destructive to lines not specifically designed to accept it.

Back to your situation. Basically, if the hot water dispenser has metal lines in it.....don't use RO water. Over time, it will damage them to the point that they will leak. And you probably won't become aware of it until significant damage has been done.

Thanks for the info asolo. Do you know what the quality of the hot water would be, coming from the insinkerator, in terms of what sitting in the heated reservoir would do to it?

It is sealed system, so I wouldn't worry that way. Probably over-stated the "aggressive" bit. They always advise no copper lines outbound from RO or distilled water units. Stainless is better -- which may be what your dispenser has in it. In the greater scheme, however, you can think about it like a tea-kettle. I remember when I was a child mom's tea-kettle was caked inside with calcium-like precipitate from years of use. Same kind of thing that happens to heating elements in water-heaters. That's what hard-water does. Distilled water is zero-ppm/TDS. RO-water is typically 5-10ppm/TDS. "Ideal" compromise for the purpose would be, maybe, 20-30ppm which is about what bottled drinking water is. RO water at mom's house is about 5ppm/TDS and her tea-kettle today is absolutely clean after 18 years of daily use. If you want to get nuts about it (like I am, it seems to me) you can buy a TDS meter for about $20.00.

However, getting a little anal here. If it was my unit, I'd run RO water in it and not get too excited one way or another. It will break and need to be replaced sometime for some reason regardless. Certainly, I would run RO water to it as opposed to tap-water. I notice my RO dispensing spigot is metal and has not deteriorated in almost two decades so am wary of over-stating.

Here is a link that might be useful: Inexpensive TDS meter

What I mean to ask is: forget about the RO...if I just run city water into my insinkerator, where it sits, heated, in a reservoir...what will the water taste like, and what will be its quality?

Does the RO system's output pressure meet the hot-water dispenser's input requirement?

My question has nothing to do with the RO system at this point.

My question is....if I just run city water into my insinkerator, where it sits, heated, in a reservoir...what will the water taste like, and what will be its quality.

Thank you. I realize my initial question included the possibility of an RO system, but I do not plan on running the purified water thru an insinkerator.

um....do I understand your question correctly? It will taste like hot city water. It will be the exact quality coming out as going in except hot. Don't understand how you might think otherwise.

My understanding is that it would taste WORSE than hot city water. My concern is that it would become scaly from sitting in the reservoir. Can anyone speak to this?

No, you won't get worse quality water from the hot water than exists originally. Actually, heating the water may cause it to lose some of it's minerals to the tank, and be less "minerally" than the same cold water. Those minerals will be deposited as scale on the tank.

Make sure your Insinkerator is one of the newer ones that has the stainless tank, as the older ones with the base metal tanks end up rusting out pretty quickly. Someone giving you one makes me think it's one of the older discontinued models.

When were the older models discontinued? Since it is still under warranty,we are about to reinstall our 3 or 4 year old insinkerator cold/hot in our new kitchen.

My water is RO water supplied by the city I live in.

I would like to replace my outdated GE reverse osmosis system which is under my sink with a separate tap and need suggestions for current water filtering systems.

I am open to suggestions!

I may install a chiller/ and heating unit too.

Off-topic....suggest starting new thread with this.

Also, don't understand. Your city supplies RO water? But you also have an RO system under your sink?