I am installing a five stage, reverse osmosis drinking water filtration system for a family member in conjunction with the installation of a on demand hot (beverage) water dispenser.
I was told by the R.O. filter rep that I shouldn’t run the filtered water through any metal lines (excluding stainless steel) or let it sit in a metal tank (the instahot tank) as it has been so stripped of contaminants by the reverse osmosis process that it is “hungry” for metals. I was given the impression that the water flowing through the hot water dispenser will take on a distinctly metallic taste if I use it.
Do any of you have experience with these issues? I would like the system to supply high quality drinking water both hot and cold but am not sure if the filter rep. was overstating the nature of the filtered water in contact with metal plumbing.
I heard a horror story once of deionized water destroying all the solder joints in a radiator just moments after it had been filled with some deionized water. If there are any similarities between R.O. and deionized water in this respect then I start to wonder if I will have the instahot tank fail in short order if plumbed with the R.O. filtered water.
My other option is to just tap into the filtration unit after the sediment and carbon filter cannisters but before the R.O. membrane for the hot water dispenser supply.
My inclination is to run the R.O filtered water through the hot water dispenser but I can’t justify doing it unless I can get a well informed source to confirm that it is acceptable.
Any insight or experiences with such an installation would be greatly appreciated.
Thanks, Karl
Edited 12/18/2002 2:36:16 AM ET by karl
Replies
Karl,
Demineralized/deioninzed water is an aggresive solvent. RO treated water is not as pure as that produced by 5 vessel demineralizer system like you would find in some commercial/industrial applications, but a 5 stage RO system will produce water that will certainly dissolve most steels, over time, including most stainless steels, (Carpenter 20 being one of the exceptions) however the horror story you heard was fiction. How much time? Depends on many variables. I don't think the water will have a metalic taste, but the tank will eventually fail.
Something to consider, since this is potable water, truly deionized water can be an effective laxative. I don't know why. You may want to consider a different treatment.
Have you had this water tested? What is the source? Is it chlorinated? (Some types are RO membranes are not compatible with chlorinated water) If you have not had the water tested, I would recommend doing so to find out exactly what is in it (that day). For $100 AAA Environmental offer a home sample kit/testing service that is very thorough.
Tim, Thank you for the in depth reply. You may have given me more info than I can actually use.
My real concern is whether or not it is going to cause problems connecting the output of a "five stage" reverse osmosis" residential water treatment system to a instant hot water dispenser.
The unit I purchased can be viewed at http://www.premierh2o.com/watts/showdetl.cfm?&DID=15&Product_ID=25&CATID=1 The hot water dispenser I plan to install can be viewed at http://www.insinkerator.com/hc1100.html
Ultimately my two issues are the taste of the water and the longevity of the hot water tank. Insinkerator says their product has a "Dura Tank" but I have yet to find a description of what this means. The last insinkerator dispenser I saw was about 15 years ago and it seemed to have a copper tank.
It is interesting to hear that even stainless steel can be dissolved by demineralized h2o. I had looked at one instant hot water dispenser that used a stainless tank as its claim to fame.
Good suggestion on getting the water tested.
If you would cast your vote on connecting the RO output to the filter, tapping in before the ro membrane or just using tap water for the Insinkerator heater it would help me interpret the in depth response you already posted.
Thanks in advance, Karl
I would not prefer to heat tap water directly if I did not know something about the water, specifically the hardness. If I had to choose between the possibility of the RO water dissolving the tank and tubing/piping or hard water scaling it up so bad it would not work well, I'd take the RO input.
I'm not a source but all it is is a filter. It isn't chemically altering the water. Ro is common in processes where chemicals are mixed in solution or water is extracted from things like orange juice.
I don't think Di and Ro water are the same thing are they?
Edited 12/20/2002 2:40:18 PM ET by Booch
Booch,
Reverse Osmosis (RO) is sometimes refered to as "nanofiltration". It is in effect a filter, but not like what you think. It is a filter on the molecular level. In reality it is a chemical separation process. The end result, water with very little impurities (dissolved solids and dssociated ions) IS the same as de-ionized water. Water is water. RO is a chemical process, (it is the removal of chemical impurities from water) but is done in a physical manner.
Osmosis is the the process in which water of "high energy" (low level of impurities) permeates a membrane in order to become at a "lower energy" (i.e. with a higher level of impurities). The driving force is called the osmotic pressure. In the reverse osmosis process, a force (pressure) is applied to overcome the osmotic pressure and reverse the process, hence the name. It is theoretically possible to force all of the water molecules through the membrane and leave behind nothing but impurities. In practical applications, a single stage of RO will extract impurities from about 75% of the water, concentrating the remaining 25%, which is sent on to the next stage and so forth until either the disired yield or quality is obtained.
RO is not used in any concentration processes, it is solely used as a means to purify water.
What you describe is true no doubt.
As for only water... I can't speak as a designer of the filtration but I do know it is used by several of the food processor manufacturers here in the state as a method of reduction of water content in food product.
In most methods there is a control system that I have supplied components for. The control system involves a couple of pumps to provide the osmotic pressure, and valves to provide hydraulic logic. The logic cycle is that the pump pushes the liquid at the filter with the filtered liquid going one direction and the concentrated original liquid going the other. After a period of time the filter media is flushed out and the valves provide logic to provide backpressure on the RO filters with "Clean water". In fact some of the logic provides more than a static pressure by giving shock pressure (pulses) to backflush the filter. Ordinarily the system is flushed then the process restarts.
It is a method to concentrate OJ but the details escape me as the last time I was involved in this process was a couple of years ago. Understand the food service manufacturers are a bit secretive so I don't doubt there are a couple of elements missing from the above design.
Chemically altered? I'm pretty sure the action is all physical filtering. There was no provision in a chemical lab water processing system for replenishment of any materials. Now stripping out particles (be they stable molecules or "hungry ions") could be construed as changing the water chemically. In my comfort understanding of chemical reactions,I expect reactants and products."The time has come," the Walrus said, "To talk of many things: Of shoes--and ships-- and sealing wax--Of cabbages-- and kings, and why the sea is boiling hot-- and whether pigs have wings"
Booch, Thanks for adding to the discussion. I am curious if you would use the RO water for the instahot heater I am installing?
Karl
Sure,
I'd process the water that way for drinking water. As for dishes and normal process water I'd probably stay with the tap.
If you have hard water then the best long term solution probably is a softener for the rest of the house. Not good to drink but great for everything else. The salt in those is used to free the rosin in the filter tank on the softening system. the salt tank displaces the impurities with the salt. That impurity collection is flushed then the salt is rinsed out with the normal well water. Unfortunately there is an amount of salt that passes thru the softening system to the home watersupply but it is really minimal.
Sounds like the system is underway at your place. good luck.
Thanks Doc and Booch for the positive vote,
The system is actually in my 89 yr old grandmothers kitchen. I hooked it up yesterday as her xmas gift.
The system seems to be working fine. The RO unit did include some kind of resistance meter to test the "purity" of the processed water and indicate if the membrane needs replacement. It reads 18 on the RO water and around 300 on tap water. The RO water out of the hot tank comes out at a reading of 30. I don't know if hot water will account for the change in readings or if that is proof that it is drawing metal out of the system.
The RO unit seems to easily supply 3 gallons in a 6 hour period. I drained the tank at noon and again at 6pm. I assume it replenished itself even quicker than the six hour interval but don't intend to try and clock its production any more exactly.
Merry Xmas to you all as well,
Karl
Tim, Thanks for the additional input. I am actually only about two hours away from installing the filtration/instahot units. I will go ahead and use the RO output for the water heater. Insinkerator makes reference to doing this in their installation instructions. They are less than specific about the connection to a filtered water source but this combined with your inclinations and my desire to have ro water both hot and cold leads me to go for it.
You and Booch combined generate a lot of interesting info on the reverse osmosis process. Thanks for keeping this thread going.
I'm at about the same stage as you regarding a RO-hot tap installation, only in my own house. If I'm to believe all I've read /been told, you have to keep that RO water far away from any metal. Consider the following:
-The rest of the plumbing's OK, its Typex. But then, all the fittings for the 'Pex are brass, and that's metal too. No one up here has even heard of plastic fittings for 'Pex.
-The only plastic taps I can find are for beer kegs.
-I guess the stainless sink is out too. If SS won't last, then granite likely won't either, and that's too expensive to take a chance on. Corian might work. Or maybe clean Grandma's old enamelware dishpan that the cat's been using for washing dishes in
-Gonna have to talk the wife out of using that $2800 worth of Paderno stainless steel cookware she's so proud of- maybe we can use it camping, where there's no RO
-Haven't seen any plastic cutlery yet that looked either respectable or sturdy -- maybe we'll have to wash the silverware in the bathroom
-I guess the Ironstone plates are out too
Two points here: Firstly, the Orange Aprons are hired for their ability to sell product, not not inform the customers, and secondly , don't believe nuttin you read on the net.If you don't trust that, check out
http://dhmo.org
And Tim, when you take a dose of salts, you add the Epsom salts to the water, you don't take them out.
Doc - The Old Cynic
Doc,
Thanks for the additional input. Everytime someone posts here I keep hoping for an absolute "do it" or "don't do it" with a brief argument supporting that position. I realize this is wishful thinking. At least everytime someone throws in another opinion I get more information to build my own argument (hopefully) that connecting the RO to the hot water was acceptable. It is now connected and either blissfully filling the tank or viciously ripping metallic elements out of the tank and plumbing.
Time will tell but I am still open to additional perspectives in the present.
Karl
I won't wish you good luck with the system because you don't need it - - it will all work just fine. I will wish you Merry Christmas and all the best for the season, though.
I would have put in a whole-house RO system, but that would have wrecked my plumbing budget for a long, long time, and the under-the-counter types usually only put out 3 to 5 gallons per day
Last RO/hot tap Combination I had anything to do with has lasted 15+ years in very hard water with only one membrane replacement, and no rust/tarnish/corrosion in the HT
Not much maple syrup produced up here without RO - - Typically it takes 32 - 35 gallons of sap to make one gallon of syrup. We used to boil that off using great whacking amounts of wood, oil, etc, but the RO concentrates that to 1.5 to 2 gal, and that gets boiled down in the traditional way
Put that in your Kyoto and smoke it (g)
Doc - The Old Cynic