RO Systems

[beltbuckle]

Apparently many people successfully use aquarium RO systems. Your rejection (350 --> 1) is a little suspicous though. That's 99.7%.

My system is a 5-stage, RO + DI. I can choose the output... I can get either RO output, which runs 35-60ppm TDS or RO/DI output. My 1ppm was for the RO/DI. The deionzer strips out darn near everything left after the RO stage.

[ajdelange]

My system is a 5-stage, RO + DI. I can choose the output... I can get either RO output, which runs 35-60ppm TDS or RO/DI output. My 1ppm was for the RO/DI. The deionzer strips out darn near everything left after the RO stage.

Now I believe it.

[Beer Baron]

Wow. I just use the RO machine in front of the grocery store and a couple of 5 gallon water jugs.

[LordUlrich]

one thing to keep in mind as far as capacity is that you can blend water. If you are building water, you should know what you have anyway, and just blend to get close, and add whatever you need after you blend with your influent. You can effectively add between 10% and 60% capacity depending on your base water. Also remember that RO water WILL leach salts and metals out of your supply system. So DO NOT store RO water in a stainless pot for a long time (more than a few hours) unless you add your salt and mineral additions when you start your system. (this is why many RO systems appear to have lower poor performance, frequently the water is blended to protect the distribution system)

One thing to potentially look into (if you are doing A LOT of brewing, like 75 gal in a week) there are some large scale RO systems which include the ability to back flush the RO membrane. I have no idea if these systems are available on a smaller scale, but i know RO membranes have been in use for ~10 years in my area (they are running like 10 million gallons per day through these systems but I suspect a smaller scale option exists)

[beltbuckle]

One thing to potentially look into (if you are doing A LOT of brewing, like 75 gal in a week) there are some large scale RO systems which include the ability to back flush the RO membrane. I have no idea if these systems are available on a smaller scale, but i know RO membranes have been in use for ~10 years in my area (they are running like 10 million gallons per day through these systems but I suspect a smaller scale option exists)

FYI the Typhoon system from airwaterice.com has this back flushing capability. They say to run it for a few minutes prior to generating RODI water for extended membrane life.

[ajdelange]

The Titan systems do not have backflush capability (though as they are put together with John Guest connectors it could be easily arranged). Instead they recommend cleaning the feed side with sodium carbonate or lye for biological fouling and citric or hydrochloric acid for inorganic (lime deposit) fouling.

Titan systems can be configured with a brine feedback valve i.e. a portion of the concentrate is fed back to the inlet side of the pump. This obviously increases both the recovery and the permeate TDS.

Yes, RO water is aggressive but then so is the water that comes out of an ordinary water softener (calcium has been removed in both cases). Everything in the permeate plumbing (tanks, pumps, pipes, valves, bibs..) should be non metallic. But that's because water stands in those pipes 24/7 and they are required to last for years. I have trouble believing that sufficient corrossion of stainless would take place over the course of, say, an overnight stand with even 18 M-ohm distilled water. It might not measure 18 Megs any more but I doubt it would have anywhere near enough metal dissolved in it to taste metallic which is really the ultimate criterion.

[beltbuckle]

I have trouble believing that sufficient corrossion of stainless would take place over the course of, say, an overnight stand with even 18 M-ohm distilled water. It might not measure 18 Megs any more but I doubt it would have anywhere near enough metal dissolved in it to taste metallic which is really the ultimate criterion.

I tend to agree with you. A lot of people parrot that RODI water can't be kept in stainless at all. I don't store my RODI water for years in stainless, but I don't have any problem storing it for a few days or weeks in Sanke or Cornelius kegs. Never tested it, but I do taste it regularly after such storage and can detect no metallic (or any other) taste.

I know water is the universal solvent but don't think a few hours or days are sufficient to yield any meaningful results with stainless steel.