Will an icemaker work with RO water?

First of all, you can make ice cubes from water produced by reverse osmosis systems. In fact, ice made from reverse osmosis (”RO”) water produces cleaner, clearer and better tasting ice cubes because most of the contaminants are removed from the water. So, just because water is purified by a certain process, (in this case, reverse osmosis), has no bearing on whether you can make ice. I prefer “clean ice” – in many cases it is perfectly clear, except for a little cloudiness in the center of the cube. Another benefit is that the cube is harder and melts slower. Most people like that as well.

So, why would an ice machine technician tell you that RO water won’t work on an ice machine? I suspect that his experience is that he has seen many situations where he is called on a service call and found that when the reverse osmosis system was disconnected and the ice-maker was connected directly to the house supply, it worked. That doesn’t mean that RO water won’t make ice cubes, however. When you supply an adequate volume of water at an adequate pressure, any ice-maker will produce excellent cubes.

The problem with an RO system on ice-makers (especially the “basement bar-type” machines) is that those types of ice machines use a large amount of water. Believe it or not, some of those machines can use 80-90 gallons of water a day! Unless you have a high volume reverse osmosis system, it is futile to try and supply RO water to that kind of ice-maker.

Another issue is pressure. Many new ice machines require 30-40 PSI (pounds per square inch) to function properly. A residential RO system drops the incoming pressure by 30-35% If you are starting out with 70-80 PSI, that is acceptable, but if the incoming water pressure is 40-60 PSI, there may be a problem. Volume and pressure are separate problems. You may have enough pressure to operate an ice machine, but not sufficient volume and it’s not as simple as adding another tank with plenty of volume and little pressure.

Sizing a reverse osmosis system is critical when you have multiple outlets, especially if one or more is an under-the-counter ice-maker. Most residential reverse osmosis systems are 24 to 50 GPD (gallons per day), which is not nearly enough for such an ice-maker. Additionally, production is reduced whenever the water temperature is below 77 degrees F, and whenever the pressure is below 60 PSI. In the real world, a 50 GPD reverse osmosis system in the Midwest may produce 20-25 GPD, when the demand may be up to 150 GPD.

However, there are solutions, and they do not have to be extremley expensive. One solution is to install a larger system, such as a 300 GPD system or a high production system. Another solution is to boost the incoming pressure with a booster pump or boosting the system pressure to 80 PSI with a Demand Delivery Pump. Look for these under out reverse osmosis systems. This type of system will provide plenty of high quality, great-tasting RO water, without running out! So, you can use RO water on ice machines (we install RO systems on very large commercial machines). They just have to be sized properly.

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This article has 33 Comments

  1. I was going to use my RO under sink unit to supply my fridge ice-maker.
    I see you are installing on commercial machines, my concern is what is used inside the ice-maker, is it copper? Will the RO water leach the metals from the inside of my fridge fittings over a period of time? My concern is for the longevity of my fridge-freezer unit and not having to replace the ice-maker unit after a short period of time.

  2. It is doubtful that a residential “line pressure” reverse osmosis system would reduce the TDS to the point of where it would leach copper. I think that this is a nothing to worry about. A home RO just won’t reduce the TDS to the point of where that would happen.

  3. Hello Mark:

    Just a note to say Hello from a former ARS buddy. I’ll be ordering a set of RO filters soon. Maybe you could give me a price break!!
    Anyway, wishing you and your family a happy holiday season.

    Take Care

    Earl E. Ewart

  4. So does the Merlin system reliably provide RO pure water at the 40 psi needed for the ‘fridge, with its low demand, even with TDS creep? How does the Merlin system prevent the fridge system being poisoned with TDS-creep water if it has very low demand, typical of ice and water only systems? Yeah, buy a flush tank — ok, but now you’re wasting 2 gallons of water every time you make ice, or make coffee, or even draw a cup of water from the fridge door.

    The Merlin system, as great as it seems, NEEDS some sort of storage tank to improve its efficiency in real world situations. Its only efficient if you can draw down more than 10 gallons per cycle of its flush system. Otherwise it wastes more water than the cheaper units.

  5. Bill,

    You are not far off. The Merlin system is great, but it’s not something I would use for a home. In my opinion, a permeate pump RO is better, much better, because it wastes less water, supplies much higher pressure, virtually eliminates TDS Creep and costs a lot less than a Merlin. A Merlin is great when you need several hundred gallons of water a day. If you need but a few, look elsewhere.

  6. We have a new everpur ro system and a new thermadore refrigerator which seem to be incompatible except for the first batch. The ice maker has been replaced and still no ice. I suspect it is the pressure/line freezing etc. What kind and where could we purchase an inline pump and or heater to make this compatible? We have the 3/8 inch blue tubing but I guess fittings on either side would allow for anything.

  7. It is not the line freezing, but rather the fridge because you are not getting enough water volume and pressure. Your RO system is the problem. Most RO systems do not produce enough pressue and /or volume to operate an icemaker. I recommend a “permeate pump” RO for this application (100 GPD with a 14 gallon tank) to work effectively. Unforteneately the Everpure system doesn’t produce enough water or pressure for it to work.

  8. Will an ice maker work with RO?

    YES, If you have a typical residential RO it should have adequate pressure to make ice. If the pressure from the RO is not adequate there’s a couple of easy INEXPENSIVE ways to fix that.

    1.) Simply increase the air pressure in the storage/ bladder tank. There is a little wiggle room here.
    Be careful not to over inflate it, otherwise you will displace the room for your RO permeate water.

    2.) Put two RO storage tanks (if you have room under the sink) in series. That will give you more than enough pressure. You dont need to purchase a commerical unit…

  9. 1. Increasing the air in the tank will decrease production, due to the increased backpressure, so it’s doubtful if that will help;

    2. While 2 storage tanks will increase the volume, it will not increase the pressure, so you must first determine if it’s a pressure or a volume problem.

  10. We just put in a RO system, which is in the basement. It is connected to the frig and no where else. There obviously is not enough pressure because I get 1/2-sized ice cubes, the tube feeder the cube tray keeps freezing up and water drips from the drinking water dispenser. I’m confused as to which side a booster pump should go on – the inlet side (before RO system) or the delivery side (between RO system and the frig). Also of note is that the run of supply tube from the system to the frig is approx. 25 ft. long. I appreciate any help! Thank you!

  11. Judy,

    I would need to know the following before I can properly answer your question:

    1. What is your imcoming pressure?

    2. What size is your RO system (Gallons Per Day)?

    3. What is the size of your tank?

    4. What size is the line to your fridge (1/4″ or 3/8″)?

    Give me that information and I can give you an answer.

  12. I have a residential RO system with a permeate pump to boost production. Since I have it in the basement, I had to put in a demand pump(1.7 gpm) to deliver water to the sink in the kitchen. When I tried to connect the RO system up to my fridge for ice and water, it caused the pump to cycle rapidly when I used the water dispenser in the door or if the ice cube tray filled. . The company I bought the system from suggested a 2nd tank between the pump and the fridge but the pump still cycles rapidly when the fridge water is used. Would increasing pressure in the tank stop this? I’m afraid of burning up my pump. I currently have it at 10 lbs PSI.

  13. Steve,

    You have several issues.

    1. The pump is capable of delivering too much water. You really need a pump that delivers .6 or .7 GPM or a variable speed pump.

    2. I would suggest only 5 psi in the second tank.

    3. A better solution is to put a “booster” pump ahead of the Permeate Pump RO system as the Permeate Pump should deliver nearly the same prssure on the outlet side as you have coming in. A 1/4″ booster pump will work incredibly well in this application.

    I have never had good success with a second tank. I would suggest a 75-100 GPD membrane in a permeate pump Ro with 3/8″ lines to all outlets and a 14 gallon tank. If that doesn’t solve your problem, then put the booster pump ahead of it and you will be amazed!

  14. Mark,

    I goofed. I just took a look at my pump again and it’s a .7 gpm Aquatec 5800 DDP. I tried putting more pressure in the tank but that just caused the pump to cycle rapidly sooner before the tank was full. Sooo, you’re suggesting to put 5PSI in the 2nd tank.

    Also, with your suggestion, you said to put a booster pump before the permeate pump? I thought the permeate pump was to boost the output of the membrane and that would negate the need for a booster pump. At least that’s what I was told by the place I bought it from. What’s different between a booster pump and a demand delivery pump? Is there a pressure switch on the booster pump but not the latter? It just seems as soon as I get any drop in pressure due to usage at the fridge, the delivery pump kicks in and just cycles like crazy. If I tried the booster pump, I would imagine that the DDP pump that I have will not work? This is getting a bit frustrating….and expensive. I really appreciate your advice. I also saw one site had a pressure switch 30/60 PSI switch that mounts on the top of of a storage tank. If you’re suggesting 5 PSI, I would imagine that 60 would be a wee bit high. This DDP pump had a power draw of .3 amps@60 psi but I’m not sure if it’ll put out 60 psi or not. Thanks again for your advice.

  15. I installed my permeate pump R.O. in the basement. It’s about a 7′ run to the R.O. faucet. I also want to hook up my fridge/ice maker. That’s about a 10′ run. I’m thinking I should be using 3/8″ tubing to everything. What do you think?

    Also the water is coming out of the faucet at a pretty brisk pace; the result is the water is cloudy at first due to the air bubbles. Should I reduce the pressure in the holding tank?

    Thanks, Rob

  16. Rob,

    3/8″ is great.

    The air in the tank should be 5-7 psi – no more, no less!

    You get air bubbles when an RO is first installed. Drain the tank 3 or 4 times over a week and it should go away.

  17. just a comment here, when I built this house they put a copper line in from under the sink to the ice maker because I told them I was going to use RO for water and ice on the refrigerator

    after about 3 years or so I noticed all sorts of black residue in the ice machine

    apparently the RO was leeching the copper line, they should have used PEX

    unfortunately, I cannot re-run the line because of the way the house was built so I now have no water (or ice) on the refrigerator

    thought I would mention that since someone asked about leeching, I’m not an expert by any means but perhaps it had to do with the length of the copper run, it was pretty long

  18. What Brian says is correct in that you really want RO water to be delivered in poly or PEX line, however, the TDS would have to be dramatically low to leach copper. There could be other issues, including dissolved oxygen and/or low pH, which if coupled with low TDS could create problems with copper.

    That said, you will never be sorry if you use plastic or PEX.

  19. I am currently in the middle of remodeling my house and will be installing a RO system to supply a refridgerator with ice and water, a freezer drawer ice maker, a built in coffee machine, an aquarium filler and a sink faucet. It will be supplied by well system. The plumber has run 1/2″ CPVC supply lines to the kitchen. I plan on using 1/4″ from there. Can you recomend the size system and if I will need a booster or damand side pump. RO system will be mounted outside with other equipment. The house is one story and the aquarium is 300 gallon if that matters? Thanks for the help.

  20. I just installed an RO system in my basement because I don’t have enought space under my kitchen sink. Also, I don’t have a spot on the sink for the RO faucet. Instead, I ran the RO water to my refridge for ice and water. I’m using 1/4 plastic tubing from the RO to the fridge. The run is about 40ft. The RO system is capable of produceing 85 gal a day, has a 2 gal storage tank, and the input pressure ranges between 40-60 psi. The water flow at the water dispencer in the fridge door is quite low and the ice maker makes a very small number of very small cubes. The place that I bought the unit from wants to sell me an on demand diaphram pump that has an internal pressure switch at 60PSI. What would you recommend I do to get the ice and water working properly with my RO system?


  21. Eric,

    Return the system and get a permeate pump RO system. I don’t know how to say this except, just to say it: “The system that you have is not what I would call a “good” system.” From the photo it appears to use “Jaco” fittings (cheap) and the membrane flush is a gimmick. Is it a lead-free faucet? I doubt it!

    Use a permeate pump RO. You are throwing good money after bad.

  22. I have just installled a Watts system to my fridge only and my issue is that the RO water causes the water dispenser on the fridge to drip. Is the water so pure it leaks through the stop valve? When I remove the RO line an re-connect the standard water line the drip goes away. Any recommendations on this issue?

  23. Dave,

    RO water won’t cause the fridge to drip.

    If the RO system is not a permeate pump, odds are that the pressure is just too low. It is also possible that there may be some debris in the valve, however I would guess it’s a pressure issue because all RO’s (except permeate pump models) lose 30-40% of their pressure in the RO process.

    The permeate pump loses nothing!

  24. We bought a house with a Culligan RO system on a well. We had no problems with our frig ice maker till we bought a new frig. The ice maker went out after about 2 months and was replaced under warranty. It has now been a year and a half and it just went out again. From what I’ve read we must have a problem with either volume or pressure. We have a 5 gal tank with 2 gal capacity located in the basement. It supplies water to our ice maker in old frig, ice maker in new frig and drinking water at sink. Can we save this RO system and do something to make it work or do we need to start over with a new system?

  25. Mike,

    The newer icemakers require more water and many RO’s can’t deliver that, as most RO systems lose 30-40% pressure in the process. This RO doesn’t:


    You will want the 100 GPD option and the high pressure permeate pump and 14 gallon tank found here:


    I have the same system in my basement with 2 icemakers, 2 sinks and a humidifier hooked up on it.

    It’s flat-out the best system we have ever handled.

  26. I looked up the system you suggested and it sounds good but I don’t understand if it’s priced at almost $1500 why you would sell it for $479. Do the filters have to be ordered or do “store filters” fit? I noticed no reviews have been listed. Is it new? I also am wondering what exactly is a permeate pump. We are looking at all options and when I asked about one at Culligan (our present RO system), they didn’t know what that was.
    I found your info very imformative and appreciate your feedback

  27. We have been waiting to hear from you before we order the RO system you suggested. We would just like more info before making a final decision. Thanks

  28. Mike,

    Sorry, I have been on Vacation a large part of the month, but the $1,500 is the retail price (including installation). We cut-out-all the middlemen and sell-direct, which eliminates lots of layers of costs.

    You can use any filters, but you will find that US Water has the lowest filter prices in the country and they are TOP QUALITY for high purity water.

    The non-electric, water-powered permeate pump “re-cycles” some of the drain water back to the inlet of the RO system, this does 4 things:

    1. Makes water much faster;
    2. Makes water of higher quality;
    3. Wastes about 80% less water; and
    4. The pressure is the same as the inlet pressure.

    … not surprised that Culligan didn’t know.

  29. We bought the system you suggested and have had it about a month or so. What a difference. So far we love it. We never run out of water and have much more pressure in our drinking water faucet.

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