There are two aspects to your question I can address: First, filtering; second, number of faucets. I'll address the second first.

You will need a heroic filter system if it is to handle the total flow of cold water from a normal kitchen sink, or a prep sink, or both. The amount of water used for drinking and cooking is only a portion of the total amount used, even if the dishwasher water supply is tapped off before the filter. It is more practical in terms of filter lifetime and inconvenience of filter changing to use a separate faucet. Further, to achieve the flow rate expected from the faucet and particularly two faucets that may be in use at the same time, either standard filters will need to be used in parallel, or larger units used to minimize restriction.

Sediment and charcoal filters will remove particles and odor from the water, and in particular will remove chlorine and chlorimine that can affect beverage taste and water taste. Generally they will not remove lead or other dissolved metals and metal compounds, or bacteria. Filtering of PCBs, benzine, etc. may be poor.

For filtering these contaminants reverse osmosis (RO) filtering is used. For a full house system, these can be somewhat complex (relative to a simple filter). Some research is called for on your part before we address any details. There are also threads on this forum on reverse osmosis that may provide some insights.

I should note that I use RO throughout my house. The system I have assembled supplies RO water to two separate pressurized tanks for supply to:

Main sink auxiliary faucet
Prep sink pot filler
Freezer ice maker
Bar sink auxiliary faucet
Centrifugal humidifier (in winter)
Hose for orchid watering
A line is in place for use on my unfinished deck

kas

Here is a link that might be useful: Key parts of my RO equipment are sourced from Spectra Pure

Looking at your water report, the only problem is chloramines which are added by your water utility as a disinfectant. The copper level is a bit high, and I have no idea how to deal with that. I hope someone on the plumbing forum will respond.

To filter chloramines, you can install a granulated activated carbon (GAC) filter which is probably what your GC has in mind. This is a fraction of the cost of RO, wastes no water and will produce water without the taste of chlorine. We went through the same process as you are now doing and concluded that all we needed were GAC filters on the lines going to our kitchen faucet and fridge ice maker. We will bypass the dishwasher and all other water lines.

You can go to considerable cost and trouble to filter out the lead and arsenic and other scary-sounding chemicals, but nothing in the report causes alarm. Everything is well below MCLs. Even the chloramines are below MCL, but you may be able to taste it. We can smell and taste chlorine at times when bacterial content at the water treatment plant is presumably high.

Cheryl

Thank you Kas and Cheryl!

I think my new plan is to use the GAC for the ice supply line and cleanup sink, and then put an RO unit with aux faucet at the island sink. I would've preferred to avoid the aux faucet, but there doesn't seem to be a practical way to do that with RO. I think that given the way we'll use the RO faucet, waste won't be a big concern and so we'll use the costco unit that does not recycle, vs the one which does.
Anyone have input on a specific RO unit - like this one from costco? http://www.costco.com/Premier-WP4-V-Reverse-Osmosis-System-with-Monitoring-Faucet.product.11257320.html

I agree with the posting by kaseki. And I would suggest going with reverse osmosis, as the quality of water produced by these systems is unsurpassed. Although the link to the system he is using is quite expensive compared to the system I have, and my filter replacements are cheaper as well.

The issues I have with the Costco system, is that it doesn't have a final polishing filter or charcoal filter after the RO membrane, and will leave your water tasting flat. This is a larger company (Premier) so they probably cheap out on the pre filters, by this meaning they probably use the same filter for the 2nd and 3rd stage. And lastly, without a DI stage after the RO membrane, the water is acidic, which can be hard on the body.

Do some research first, I just checked reviews on Amazon, and this system has a 2 star rating. I would suggest the 6-stage system I have from a company called Aquasafe Systems. The system is under $200, has the polishing filter, provides alkaline water, and produces 100 gallons per day, and the system from Costco probably only does 50, maybe 25.

Here is a link that might be useful: Aquasafe Systems

I concur with MichaelsAd that for cases where higher pressure supply is not needed, such as a single faucet, a quality non-pumped system is appropriate.

My link should only be used to get to the Spectrapure website. The particular page that appears seems to change with whatever is being promoted. My system is not at all like any on the page I just viewed. I think it is only shown in a particular application note buried somewhere on their site. In any case, my system is not appropriate to a modest requirement.

kas

Thanks MichaelsAd and Kaseki, that does look like a nice and reasonably priced system which would fit my needs. Still trying to figure out how to fit filtration in the physical space and in the budget.

It is always possible, if a basement with space is available, to mount the assembly to a wall or to the joists and plumb its output to the sink base area using polyethylene tubing. (See Portage Supply's web site for applicable components such as tubing and John Guest fittings.) Changing filters where one can stand up is vastly more comfortable and more efficient than trying to change them by reaching under a sink. And spills will be less problematic.

Location will depend somewhat on your options for transporting the waste (brine) to a drain. Of course, it too could be plumbed back to the area under the sink where the device's directions might suggest it go, but that is only a option, not a requirement.

kas

No basements in Florida, but I'm hoping we can mount a unit in the garage and then run one cold water line which splits in the kitchen to serve 2 dispensers and the ice maker. That would be the ideal physical solution, but I'm worried about the expense of the water line. The second choice will be to just put the RO unit at one sink, and rely on GAC for the ice maker. Minimizing the damage of spills and leaks is important, I've experienced ruined wood floors and hope not to do so again.

I need to purchase a RO system. We have municipal water that tastes bad. I have a sediment and carbon whole house filter and currently have the Watts Premier Pure 4-stage RO system. I've had it for almost 2 years with a few leaks, but the water is great and I'm happy with it.

We're moving and I need a new RO system. I'd buy the Watts system again, but I've been reading the reviews on Amazon, and they are very uneven. It sounds like you need to be lucky with the Watts Premier system or you'll get leaks and rubbery taste (I'm half-lucky, since I've had leaks, but no rubbery taste).

The Aquapure system looks OK, but how difficult is it to change the filters? And are they proprietary filters like the Watts filters (which are incredibly easy to change), or can you buy them at big box stores? Any experience with rubbery taste with the Aquapure system?

Please help me choose: The Watts Premier 4-stage system or the Aquapure Maxiumus II 6-stage system. Both fit my budget. There are no reviews of the Aquapure on Amazon, but there are 18 5-star reviews on the Aquapure website, which makes me very suspicious!! They must edit their reviews!!

If you have either of these systems, please tell me how you like it. TIA.

All the RO cartridges that I've seen (excluding extra large ones) are the same size and take standard RO membrane assemblies. However, the standard is in shape, not necessarily in performance. I wouldn't buy them at a big box store unless their filtration efficiency is listed and you trust the source; RO system suppliers will specify the actual performance of the membranes they sell.

RO filters should probably be changed after around 1.5 years, but this obviously varies with how good the pre-filtration is, the quality of the water, and the amount used.

To change membranes one needs a bit of strength because the cartridge cover screws on over an o-ring and the plastic-on-plastic threads tend to bind a bit. I use a pair of strap wrenches (Rigid is one manufacturer) to loosen mine.

Turn off the feed water first, then relieve the pressure.

kas