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Reverse Osmosis or Undercounter Filter?

Posted by txjoyce (My Page) on
Sun, Feb 5, 12 at 12:40

We're remodeling the kitchen and currently have a 12 year old Culligan reverse osmosis machine. We like the quality of the water, waste is okay (3:1 ratio), but newer Culligan's are 1:1. On the newer models, we would be able to change filters ourselves vs service call & pricy filters.

We're debating if we should purchase another RO or just go with an undercounter filtration system.

Our major concerns are:

Water Quality
Waste ratio
Ability to maintain ourselves.

What would you do?


Follow-Up Postings:

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RE: Reverse Osmosis or Undercounter Filter?

Things have, indeed, changed in the last 12 years. I can understand the desire to consider upgrade.

If you're accustomed to RO water, I suspect you may not be satisfied with less-than-that filtration. Although the under-counter filters do perform as specified, you'll still not get the quality you're accustomed to from RO.

The filters will still be pricey, but if they're easy to change that's certainly a plus.

I have the Kinetico versions but I understand the new Culligan units are quite nice. They all do the same thing the same way. The differences are in convenience features and the cost to obtain them.


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RE: Reverse Osmosis or Undercounter Filter?

Since you're happy with RO water why change?

You've gotten reliable and satisfactory service from your 12 year old Culligan so I'd take a hard look at what the new Culligan RO offers and at what price? Less expensive consumables and escaping routine service charges will add up over the next 12 years and offset the cost of a new Culligan RO.

It's also worth considering an industry standard RO that is made with US components and assembled in the US at a far lower cost than a name brand RO with equal reliability and performance. Industry standard filters and parts are available almost everywhere and at VERY low cost compared to the brand names.


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RE: Reverse Osmosis or Undercounter Filter?

One of the challenges is it's very difficult to find the waste ratio on most RO units -- I've found the lower the cost of the RO unit, the greater the waste ratio. Just my experience.

I suspect we will stick with RO because we do like the water quality -- just wondered if any of the undercounter filters came close to that quality


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RE: Reverse Osmosis or Undercounter Filter?

"just wondered if any of the undercounter filters came close to that quality" ... NO.

Regarding waste ratio numbers, you'll find that most manufacturer provided numbers are derived from testing under specific and stringent bench conditions that are rarely achievable in the field.

It has been my experience that people use much less RO water per day than they think they will when shopping for an RO so the waste(?) is much less of a consideration than environmentally conscious people think it is.

You can save far more energy and waste far less water than an RO wastes if you install a recirc pump so you don't have to wait for hot water to arrive at the farthest sinks from your water heater... now THAT wastes water you can see on your water bill in dollars.


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RE: Reverse Osmosis or Undercounter Filter?

justalurker makes some good points about actual waste vs theoretical waste.

On the convenience side -- which you'll notice frequently, if not every day, in-use -- I would encourage you to also consider replenishment rate, flow-rate from the spigot, and whether or not the spigot flow-rate diminishes as the tank empties. These things are affected by inbound line pressure, line size within the unit and out to the spigot, whether or not the tank refills against back-pressure, and whether or not the spigot output is controlled by holding-tank air-pressure. Everybody's getting better at this but some are MUCH better than others.

Some folks don't care much one way or the other but, if you do, I would recommend looking into it.

Also, some folks are interested in and good at DIY. If you are, you can save a lot of money. If not, you will want to consider availability and price from local vendors. I must observe from many posts here over the years, however, that many people who thought DIY would be easy found it was quite confusing and easy to botch. Reports have run the gamut from line leaks to wrong-way connections. If you have the interest and ability, by all means go ahead. Just suggesting you not pretend about it.


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RE: Reverse Osmosis or Undercounter Filter?

Thanks everyone... DIY and plumbing of any kind don't mix in our house.... sooner or later we'll have to call the plumber, so now we just kill the fiction and call them upfront!! We'll probably go with the new Culligan system - we're at the point that we need to have the main RO membrane replaced, so we might as well spend a bit more and have a more efficient system.


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RE: Reverse Osmosis or Undercounter Filter?

I would have big doubts that that RO would have a 50%. A 1:1 ratio would require special applications, pressure and equipment. It might approach that ratio if it were a nano-membrane but not an RO.

What model is it?


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RE: Reverse Osmosis or Undercounter Filter?

Likewise, I'm not aware of any residential system that has a 1:1 ratio. What people call "waste water" is better thught of as "flush water" - in that this water flushes from the membrane everything the membrane doesn't allow to pass.

Water use in residential systems is so low (rarely more than several gallons a day) that I don't thing the waste to permeate ratio is much of a consideration. If you just don't like to send water to the drain, get a traditional residential RO system with a permeate pump.


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RE: Reverse Osmosis or Undercounter Filter?

I believe you can get somewhere between 1.5:1 to 1:1 by running a 2nd RO membrane inline, basically sending the wastewater from the first membrane into the 2nd one. But you need higher than 65 psi into the first membrane, or else a booster pump. This also increases the production rate of RO water.

But I agree the amount of waste water in typical residential use is not significant.


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