RO setup

[bassmaster911]

What is your opinion on the best RO setup for home use? Where and what to purchase? Thanks!

 

[944play]

I'm happy with this one:
http://www.bulkreefsupply.com/store/75-gp-5-stage-ro-system-no-di.html

Be aware that it will take a few hours to draw off enough water for a batch.

 

[bassmaster911]

Thanks for the reply. I was wanting to find a good unit to mount under-sink that would have its own faucet, easy to find filters, good reviews, and hook up without a saddle valve. Any suggestions? Thanks.

 

[mabrungard]

Be prepared to store alarge volume of RO water in order to have it ready for the brew day. Most low-cost RO units have a relatively low RO water output and it will seem like forever to draw off enough for brewing. 50 gal/day is typical for inexpensive units. That's about 2 gal/hr. Since a typical 5 gal batch requires 8 to 10 gallons, that is a long wait! An undersink mounting location may leave you without a place to set a water container.

 

[audger]

you should also consider how much waste water the system uses to produce 1 gallon of RO water. the membrane works by concentrating contaminants on one side, and letting pure water pass thru the membrane to the other side. the water with all the contaminants needs to be flushed periodically to speed up the process.

some cheaper RO machines waste 4-6 (or more) gallons of water per 1 gallon of pure RO water produced. more efficient ones will only waste 1-2 gallons per gallon of RO water.

 

[bassmaster911]

I am okay with it taking a while to collect enough water to brew. I will probably start collecting the same time I make my starter. I thought it would be nice to have for coffee and drinking water. What is a good brand to go with?

 

[mabrungard]

The most important thing is the brand of membrane. The rest of the apparatus is off the shelf parts that every manufacturer uses. I recommend Filmtec membranes as a good brand. If you happen to have an ion-exchange water softener in the house, feed softened water to the RO unit and your membrane will last far longer. Do get a TDS meter when purchasing an RO unit so you can confirm that the water quality is high. Replace the membrane when the TDS measurements go up.

 

[ajdelange]

you should also consider how much waste water the system uses to produce 1 gallon of RO water. the membrane works by concentrating contaminants on one side, and letting pure water pass thru the membrane to the other side. the water with all the contaminants needs to be flushed periodically to speed up the process.

some cheaper RO machines waste 4-6 (or more) gallons of water per 1 gallon of pure RO water produced. more efficient ones will only waste 1-2 gallons per gallon of RO water.

What determines allowable recovery is the 'limiting salt' i.e. the one most likely to precipitate on the membrane. Calcium carbonate is the usual candidate but as has been noted, feeding with softened water lowers calcium to the point where calcium carbonate is not likely to be the limiting salt nor is calcium sulfate which is another strong candidate. Assuming nothing too exotic in your water silica may be the thing that limits.

Fancier systems allow adjustment of recovery to match the feed. Recovery of better than 50% (less than 1 gal brine per gal permeate) is possible if the feed is soft and free of silica. Simple systems usually solve the limiting salt problem by keeping the recovery low enough that even quite hard water can be processed. It should be clear, however, if your water is supersaturated WRT CaCO3 going into the device that CaCO3 will precipitate on your membrane(s).

 

[bassmaster911]

According to the local water district my CaCO3 is 142 ppm(from 2010). I am guessing this is high enough to clog the membrane faster than average.

 

[ajdelange]

That's actually the alkalinity. If you will post the calcium (mg/L) content (sometimes expressed as 'calcium hardness' in ppm as CaCO3), sulfate and silica and pH I will give you approximate allowable recovery rates. If all your hardness were temporary (i.e. all the calcium paired with alkalinity) then your maximum recovery would be limited (by calcium carbonate) to 22% assuming your pH is 7. The cheap GE RO units sold for a little over $100 at home improvement stores have such low recovery that you would be fine with one of them. If, OTOH, your pH were 8, then the water is already saturated and would have to be softened before feeding to the RO unit.

 

[bassmaster911]

That's actually the alkalinity. If you will post the calcium (mg/L) content (sometimes expressed as 'calcium hardness' in ppm as CaCO3), sulfate and silica and pH I will give you approximate allowable recovery rates. If all your hardness were temporary (i.e. all the alkalinity paired with calcium) then your maximum recovery would be limited (by calcium carbonate) to 22% assuming your pH is 7. The cheap GE RO units sold for a little over $100 at home improvement stores have such low recovery that you would be fine with one of them. If, OTOH, your pH were 8, then the water is already saturated and would have to be softened before feeding to the RO unit.

CaCO3-142 ppm
Calcium-38.4 ppm
PH-7.29
Sulfate-58.1 ppm
Carbonate hardness-1.65 ppm

 

[afr0byte]

Hmm, I thought Martin said at one time that softeners remove hardness but not alkalinity. Does this mean that if almost all of my hardness is temporary, that I wouldn't benefit much from having a softener before an RO unit?

EDIT: N/m, I don't believe I read you post correctly.

 

[ajdelange]

CaCO3-142 ppm
Calcium-38.4 ppm
PH-7.29
Sulfate-58.1 ppm
Carbonate hardness-1.65 ppm

With those numbers calcium carbonate is definitely the limiting salt and recovery would have to be 12.8% or less. A softener is definitely wanted here.

BTW I can't make out what the 1.65 ppm is. Carbonate hardness usually means alkalinity and the alkalinity is 142 ppm or at least I am assuming that the phrase 'alkalinity as CaCO3' appears with the 142 ppm number.

 

[ajdelange]

Hmm, I thought Martin said at one time that softeners remove hardness but not alkalinity. Does this mean that if almost all of my hardness is temporary, that I wouldn't benefit much from having a softener before an RO unit?

EDIT: N/m, I don't believe I read you post correctly.

You wouldn't have been confused if I had written 'calcium paired with alkalinity' rather than the other way round. I edited the post to read that way.

And yes, that is true about the typical home ion exchange softener. It exchanges sodium for polyvalent metal ions and that's all it does but there are other ion exchange technologies (used, for example, in the reef aquarium setups that many brewers seem to use) that exchange hydrogen ions for all cations and hydroxyl ions for all anions. Net result: all ions (except H+ and OH-) are removed and replaced with water.