different types of DI available

[mx_tang]

I have 4 different types of ion exchange resins that I can currently buy for FRAG and the other locals.

Here are the available DI resins:


Industrial grade @ +10Mohm = $7/refill

Color changing @ +10Mohm = $10/refill

Pharmaceutical grade @ +15Mohm = $9/refill

Nuclear grade @ 18.3Mohm = $10/refill

18.3Mohm is the highest theoretical resistivity that ultrapure water can attain. The pharmaceutical and nuclear grade resins need to be the last stage in at least a 2 stage RO/DI unit to further polish the water acheive their resistivity rating. For instance, you could have the industrial or color changing DI in the first stage, and the pharmaceutical or nuclear grade in the last stage. If you have multiple DI stages (3 or more), all but the last one can be the industrial grade to achieve up to 15-18.3Mohm resistivity.

I've used the industrial grade resin in the past with great success, but some people have expressed interest in buying a higher quality resin at an affordable price. Other types of resin require you to prefilter the water, running it through RO, having a degassing stage, a separate bed cation DI, a separate bed anion DI, a mixed bed DI, at least 2 polishing mixed bed DI's, a UV light, a submicron filter, until finally hitting the pico-rated ion exchange resin.

Any of the DI mentioned above will get you +10Mohm. Once it filters through the second membrane, you should have nearly 15-18Mohm, and the final polish can potentially give you to 18.3Mohm water. If you don't have extra stages, I bought a case of extra clear filter housings, since a few people wanted them. They were $20 without the speedfittings or a bracket, but our nice vendor threw in a bracket and speedfittings for $25 shipped. Anyone who wants filter housings for additional prefilter or DI stages can also pick one of these up from me.

The last thing I'd like to mention is the conversion factor between resistivity, conductivity, and total dissolved solids. Resistivity is the inverse of conductivity and vice versa:

1 / conductivity = resistivity
therefore
1 / .055µS/cm (microsiemens/cm) = 18.3Mohm (Megaohm or Megohm)

1 / resistivity = conductivity
therefore
1 / 18.3Mohm = .055µS/cm

Conductivity is twice the amount of TDS in ppm or mg/L, or TDS is one-half the amount of conductivity in µS/cm:

X mg/L or ppm TDS x 2.0 = µS/cm

Y µS/cm x 0.5 = mg/L or ppm TDS

If you're still interested in learning about water, take a look at Charles Riley Jr's Unique and Unusual Properties of Water (http://www.pdhonline.org/courses/c104/Unusual%20Properties.pdf) PDF.

[mx_tang]

I forgot to mention that I currently have the industrial and nuclear grade resin available.

[mx_tang]

I really don't want to sit on 10ft³ resin, but we can get them for $5/pack again if enough of us figure our yearly DI needs. I know it's only a $2 savings/refill, but some people who use a lot or RO/DI water would really benefit from the savings (10+ packs/year). I'm just seeing whether there's enough demand for this...if not, $7 fairly cheap for the industrial type.

Just as a reference, I've made a TDS chart with the amount of water you should expect to receive from this type of resin:

ppm TDS.........gallons/cartridge
1....................2714
2....................1357
3....................905
4....................679
5....................543
6....................452
7....................388
8....................339
9....................302
10..................271
11..................247
12..................226
13..................209
14..................194
15..................181
16..................170
17..................160
18..................151
19..................143
20..................136
21..................129
22..................123
23..................118
24..................113
25..................109
26..................104
27..................101
28...................97
29...................94
30...................91
31...................88
32...................85
33...................82
34...................80
35...................78
36...................75
37...................73
38...................71
39...................70
40...................68
41...................66
42...................65
43...................63
44...................62
45...................60
46...................59
47...................58
48...................57
49...................55
50...................54

60...................45

70...................39

80...................34

90...................30

100..................27

200..................14

300...................9

400...................7

500...................5

600...................5

700...................4

800...................3

900...................3

1000..................3

1100..................2

1200..................2

1300..................2

1400..................2

1500..................2

2000..................1

2500..................1


Find the amount of gallons/DI cartridge you are able to produce with your average TDS and divide that into the total number of gallons you plan to make/year to find how many cartridges you need.

For example, if I have 25ppm TDS, then I can make ~109g DI water per cartridge. If I plan on making 55g DI water per week, then I'll need 1 DI cartridge every two weeks or ~26 DI cartridges/year. If you run multiple DI stages, then you'd wouldn't need quite as many as you'd be effectively maximizing your DI cartridges before they became completely exhausted and started leaching TDS back into the water.

[AZDesertRat]

Mike, I'll take 2 of the industrial grade if you can bring them to FRAG.

A.J.

[kirstenk]

Do you have any for sale now?

[mx_tang]

Yes, I still have all 3 types of the resin. I don't know exactly how many units of the pharmaceutical and nuclear grade I have left, but I just packed 1ft³ of industrial resin last week.

[AZDesertRat]

I'm ready for a couple more myself.