Reverse Osmosis: To DI or not to DI?

[billr1]

I'm sure this has been covered already somewhere but I wasn't able to find the answer so hopefully someone can help. I just bought an RO system which has a bypassable DI stage. As the very scant instruction sheet says, "Blue Tube is for the drinking water. White Tube is your DI water."
I bought this system so I wouldn't have to schlepp distilled water from the grocery store every time we brew. Essentially, when we brew we mix tap water with distilled (anywhere from 25 - 50% depending on the type of beer). So which tube should I be using to replace the distilled water - the blue "drinking water" tube or the white "DI" tube?

 

[helibrewer]

Does your RO system have a stage that adds back some minerals for drinking water? If so, you probably want to use the DI tube.

 

[billr1]

It's not real clear whether it does or not. The instruction sheet is pretty much useless. Here's what the description said on the eBay auction I bought it from:

DUAL USE REVERSE OSMOSIS WATER FILTER SYSTEMS

DI FOR AQUARIUM USE OR ANY OTHER APPLICATION NEEDING DI

DRINKING WATER AND COOKING AND OTHER HOUSEHOLD USE

2 OUTLET.

1. FOR DI OUTLET WITH TUBING AND STRAIGHT BALL VALVE.

2.DRINKING VIA INLINE CARBON FILTER FOR TASTE AND ODOR REDUCTION FILTER CONNECTS TO STRAIGHT VALVE





COMES WITH THE FOLLOWING

==========================

1. STAGE SEDIMENT FILTER 5 MICRON

2ND STAGE CARBON BLOCK FILTER

3RD STAGE GAC WATER FILTER

4 STAGE MEMBRANE 80 GALLON PER DAY

5 STAGE DI WATER FILTER OR INLINE CARBON FILTER GOES TO TUBE WITH STRAIGHT BALL VALVE. The Filter cartridge is clear.

you can see when it turns brown its time to change the DI

6TH STAGE INLINE POST CARBON FILTERS attached to a straight valve for drinking water

FIRST HOUSING IS CLEAR TO SEE WHEN TO CHANGE THE SEDIMENT FILTER ( WHEN IT TURNS BROWN ITS TIME TO CHANGE)

GARDEN HOSE ADAPTER ( PLEASE LET US KNOW IF YOU NEED A FAUCET ADAPTER IF NOT TOLD WE WILL SEND A GARDEN HOSE ADAPTER)

2 STRAIGHT VALVE




http://www.ebay.com/itm/181260322384?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT

 

[helibrewer]

I would just be guessing but it sounds like the drinking water is taken prior to going through the RO membrane? I would use the DI for brewing and treat it as if it has no minerals. You can always send off a sample of the DI to Ward for analysis...or send a sample of each and see the difference. You want to use the water that comes from the small storage tank if that helps.

 

[billr1]

I may do just that (send both off for testing). Would like to see how they compare. Both stages are definitely after the RO membrane though. And there was no holding tank with this system. It was labeled as a "portable" system. It actually serves my purposes well (or rather will once I figure out which post-filter to use) because I can hook it up to a garden hose connection type faucet, and I have an extra keggle which I'll be using for a holding tank.

 

[Auger]

It is a question of purity needed, I guess. Reverse-osmosis will remove any contaminants and give you clear, pure, drinkable water. If you run through the deionization stage as well, this basically strips the water of anything it has left in it, including any buffering capability. For brewing purposes, just the RO stage is probably sufficient. I used to use full-on RO/DI for making reef aquarium water - I basically needed to strip out everything that wasn't a water molecule, then add everything I needed back in with salt mix.

 

[trimixdiver1]

Yea, the RO membrane doesn't reject 100%. The DI stages are to remove what the membrane doesn't. Theoretically you could just use a 2 stage (cation, anion) DI bed and you can do the same as the membrane, but the bed would foul quickly and need to be regenerated. I had a 2 membrane system with 2 of each DI beds, so I could switch beds while I regenerate the used one. This was for my dearly departed 800g reef tank system that I lost in the 2008 snowmageddon. Ahhhh 8 years and probably $20k all gone because the gas company had a faulty station trip.

 

[beavers]

Just wanted to throw this out there. Not sure if the same applies to brewing, but my understanding is that truly deionized water is considered unsafe to drink by some experts.

http://puretecwater.com/safe-to-drink-deionized-water.html

Beyond that, I'm wondering if it's even worthwhile to put the energy and effort into removing every last mineral when you're just going to have to add some back in.

 

[trimixdiver1]

Just wanted to throw this out there. Not sure if the same applies to brewing, but my understanding is that truly deionized water is considered unsafe to drink by some experts.



http://puretecwater.com/safe-to-drink-deionized-water.html



Beyond that, I'm wondering if it's even worthwhile to put the energy and effort into removing every last mineral when you're just going to have to add some back in.

As long as you get it lower than the limits for the beer style your brewing, it should be ok. If you brew a lot of pilsners then yes, but for IPAs and darker ales, no, unless your tap water is really hard.

 

[GotPushrods]

There is (almost/probably/catch-all caveat) no need for DI in brewing. A well-functioning RO membrane will run at 98%+ rejection and give you water lower in ions than any profile you will want for brewing beer. (My tap starts at 500+ TDS, so I'm not just assuming 'good' starting water)

If this is not the case, then the DI stage is a band-aid and you have bigger problems.

You'll want a TDS meter to monitor the health of your RO membrane. Check the TDS of your RO-only water and report back. I can almost guarantee you don't need to spend money on DI resin.

 

[Spartan1979]

There is (almost/probably/catch-all caveat) no need for DI in brewing. A well-functioning RO membrane will run at 98%+ rejection and give you water lower in ions than any profile you will want for brewing beer. (My tap starts at 500+ TDS, so I'm not just assuming 'good' starting water)

If this is not the case, then the DI stage is a band-aid and you have bigger problems.

You'll want a TDS meter to monitor the health of your RO membrane. Check the TDS of your RO-only water and report back. I can almost guarantee you don't need to spend money on DI resin.

Is a cheap TDS meter sufficient for this purpose?

 

[GotPushrods]

Is a cheap TDS meter sufficient for this purpose?

Yes. A TDS meter is actually just a conductivity meter, which estimates dissolved ions. This isn't too difficult to design and implement cheaply.

You're not splitting hairs here, just getting a relative sense of ions.

"My starting water is X, and my RO water is 2% of X".

"Hey, my RO water is now 8% of X, time to replace the membrane"

 

[LuckyBeagleBrewing]

I use DI with RO because it removes all doubt without testing the water all the time. Is it more expensive? Yep. Do I get completely stripped water? Yep.
This way I can build whatever profile I desire and know with confidence I have complete control. Do I need DI? Probably not since the RO system measures 2ppm tds on the out. What the DI also does is act as an insurance policy for my RO system. When it drifts upward, my output from the DI compensates for it. It does use DI resin but not very fast at all.

Hope this helps.

 

[billr1]

Don't take this the wrong way but I think you guys are doing the same thing I found on most the other posts asking about RO and/or DI water - assuming that I plan on brewing with 100% RO/DI and building the chem profile back up from that blank slate. That is not the case. I only plan on using it to dilute my tap water (which I've had tested and know the profile of). For instance, the magnesium in my tap water is 40 PPM. According to most the sources I've read, 30 PPM is about as high as you want to go for brewing. So the only way I can cut that is by diluting with a minimum of 25% water that contains 0 PPM of magnesium. Essentially I'm looking for something that will give me 0's across the board (Ca, Mg, Na, etc.) to dilute my water with. From what you guys are saying, it sounds like DI will do exactly that for me (which is cool because it was getting to be a huge PITA to buy and haul distilled water from the grocery store every brewday!) So I really appreciate the input!

 

[GotPushrods]

Don't take this the wrong way but I think you guys are doing the same thing I found on most the other posts asking about RO and/or DI water - assuming that I plan on brewing with 100% RO/DI and building the chem profile back up from that blank slate. That is not the case. I only plan on using it to dilute my tap water (which I've had tested and know the profile of). For instance, the magnesium in my tap water is 40 PPM. According to most the sources I've read, 30 PPM is about as high as you want to go for brewing. So the only way I can cut that is by diluting with a minimum of 25% water that contains 0 PPM of magnesium. Essentially I'm looking for something that will give me 0's across the board (Ca, Mg, Na, etc.) to dilute my water with. From what you guys are saying, it sounds like DI will do exactly that for me (which is cool because it was getting to be a huge PITA to buy and haul distilled water from the grocery store every brewday!) So I really appreciate the input!

40 ppm before RO will mean about 0.5 ppm after. You will never know that half-PPM is there, hence why I say DI is absolutely not necessary.

Dilute or use straight and build up, the ONLY thing the DI stage will do is make you feel better.

 

[billr1]

Aha - good to know! That's pretty much exactly what I was wondering about (and it also clears up another question I had).
Well, since the DI filter is already on there and it's not costing me anything extra to use it, I may as well. And if it ever craps out, I'll just bypass it altogether (rather than going to the trouble and expense of replacing it).

 

[trimixdiver1]

Aha - good to know! That's pretty much exactly what I was wondering about (and it also clears up another question I had).

Well, since the DI filter is already on there and it's not costing me anything extra to use it, I may as well. And if it ever craps out, I'll just bypass it altogether (rather than going to the trouble and expense of replacing it).

Look online, you can regenerate the bed.

 

[Spartan1979]

There is (almost/probably/catch-all caveat) no need for DI in brewing. A well-functioning RO membrane will run at 98%+ rejection and give you water lower in ions than any profile you will want for brewing beer. (My tap starts at 500+ TDS, so I'm not just assuming 'good' starting water)

If this is not the case, then the DI stage is a band-aid and you have bigger problems.

You'll want a TDS meter to monitor the health of your RO membrane. Check the TDS of your RO-only water and report back. I can almost guarantee you don't need to spend money on DI resin.

I just got an RO system and I had been wondering how I would know if it was working properly. Thanks for the advice on the TDS meter.

I bought one and tried it out yesterday. My tap water read 175 and the RO was at 12.

 

[trimixdiver1]

I just got an RO system and I had been wondering how I would know if it was working properly. Thanks for the advice on the TDS meter.



I bought one and tried it out yesterday. My tap water read 175 and the RO was at 12.

Do you have a DI stage? If not, that's what will get you to zero.

 

[ScrewyBrewer]

Deionized water is not safe for drinking, or so I've been told, please keep that in mind. Reverse osmosis water is safe for drinking and is what I use when building my brewing water profiles. Another thing to point out is that DI water is not to be confused with distilled water, which is safe for drinking and just about the same as RO water. I'm sure everyone already knows this, but it's worth repeating.

 

[Spartan1979]

Do you have a DI stage? If not, that's what will get you to zero.

No DI stage, but is it necessary to get to zero?

 

[GotPushrods]

No DI stage, but is it necessary to get to zero?

Not at all. A TDS reading under about... let's say (I'll make up a number here) 25 would be just fine as a starting point. With the vast majority of input waters and membranes, it will be lower than that anyway.

 

[trimixdiver1]

Not at all. A TDS reading under about... let's say (I'll make up a number here) 25 would be just fine as a starting point. With the vast majority of input waters and membranes, it will be lower than that anyway.

When I was using it for a reef aquarium, zero was the goal, but for brewing, as long as it gets you low enough to be able to build your water up is ok.

 

[ScrewyBrewer]

I have a sediment filter, carbon block filter and RO membrane that's only 3 months old, the TDS reading was .007 out of the box and its still the same today.

 

[john3322]

i think you can use not to DI