Cheap source of DI resin?

[DaveS]

1) stuff that is packaged for the aquarium trade is overpriced. If you can find it from another industry it can often be cheaper- look at the 2 part solutions for example.

2) stuff from Costco is generally cheaper than the equivalent elsewhere.

 

So, I'm wondering if this is a cheaper source of DI resin. It's $150 for 4 large bags of resin but nowhere does it provide a weight so it's not obvious what the cost comparison is.

 

It's refills for this spotless car wash product. Basically a DI system to provide 0 TDS water to rinse a car. The DI chambers are very large from the picture but again it provides no indication about volume or weight. The only hard numbers I found are at the bottom:

 

Expected Yield:

 

Input TDS Expected Yield (# of Gallons)

50 ppm 1600 gallons

100 ppm 800 gallons

200 ppm 400 gallons

400 ppm 200 gallons

 

So basically 1 fill eliminates 80,000 TDS. For $150 you get 2 refills for it's $75 to eliminate that 80,000 TDS. The missing data point here is- how much TDS does 1 lbs of DI resin typically remove? If someone knows that, please post up so we can see if this source would be a cost savings.

 

For comparison, BRS sells a 7.5 lbs bag of resin for $55 but it can get as low as $44. Shipping costs extra with BRS whereas it's included in the Costco item.

[iceman]

When I had a much larger system, I would go in, every so often, with a friend to get resin from resindepot.com (link: http://www.resindepot.com/shopdisplayproducts.asp?id=618&cat=Mixed_Bed_Ion_Exchange_Resin ). We would get the 1 cubic foot of the Purolite NRW37 Mixed bed Ion Exchange Resin. This amount is equivalent to about 60 refills (using 10" refillable canisters). We would package the resin in air tight containers to keep air and moisture out and they would last a good while. The price used to be $200 shipped, but it has gone up some. This is for the non-coloring changing resin.

 

The 7.5lbs of resin from BRS makes 5 refills of a 10" canister (basically $11 per refill). The resin depot comes out to about $4.00+ per refill.

 

With the Costco stuff, it states the main unit uses two 20" canisters, so one refill (2 bags) is needed to refill both of the 20" canisters. Not sure how much the 20" canister holds...it would be interesting to know to help compare.

[hypertech]

Remember to solve the storage problem if you buy in bulk. Unless you can seal it up really really well, it will lose effectiveness from exposure to air.

[bill stine]

Remember to solve the storage problem if you buy in bulk. Unless you can seal it up really really well, it will lose effectiveness from exposure to air.

 

easy solution for that, use one of those food sealing gadgets that lets you buy bulk food items then break them into smaller packages and vacum seals them for freezing.

 

Should be easy enough to determin the weight of a refill then divide it up and vacum seal it for storage.

[Origami]

I exchanged emails with BRS to get some idea of the relative size of a regular, 10 inch long 2.5 inch wide refillable cartridge relative to the 20 inch long, 4.5 inch wide cartridge in this system. Volume-wise, you need 7 times the media to refill the larger cartridge. BRS sells 1.25# of resin for 1 cartridge. Thus, 8.75# is needed for a "double big-blue" used in this "spotless car wash" product.

 

So, if the Costco site has 4 bags for $150, that's $37.50 a bag. And, if you can get 7 standard refills out of one of these bags, then that's $5.36 per refill (before shipping).

 

I was looking for an inexpensive source of resin a few weeks ago, but wasn't successful. I think that I was focused on Resintech MBD-30, color indicating resin. I think that may be what BRS sells, but don't know for sure. The Purolite NRW-30 sounds good, too, though it's not indicating. (A cubic foot weighs around 45 pounds, so it's equal to 6 7.5-pound bags of BRS refills.)

 

Here's something, though, to ponder: According to TheFilterGuys (http://www.thefilterguys.biz/bulk_di_resin.htm), 1 gallon of resin refills 4 standard 10-inch cartridges. At 231 cubic inches per gallon, that's about 58 cubic inches per refill. A cubic foot, then, should only yield 30, not 60, refills. As a sanity check, I checked the density of both resins and they're about the same. This is in the ballpark of BRS' conversion factor which is 6 refills per 7.5#, or 36 refills per cubic foot. Keep this in mind when comparing costs. (The discrepancy in number of refills may come from the fact that a 2-1/2 inch refillable cartridge is actually larger than 2.5 inches in cross section, and may not take into account packing the resin into the cartridge.)

 

A quick search for a color-changing mixed bed di resin sold by the cubic foot yielded this place which, coincidentally supplies resin for a "spot free," clean rinse system (similar to what you found at Costco, Dave). With shipping, it's $284 for a cubic foot. If you can get 36 refills out of it, it works out to $7.88 per refill.

http://www.clearinse.com/Accessories/Bulk-Resin

 

ResinDepot's non-indicating resin works out to $239 per cubic foot. At 36 refills per cubic foot, that's $6.64 per refill.

[iceman]

Nice job, Tom. I was definitely off in my remembering how many refills we got out of the bag (sorry if I misled anybody). I just remembered it was a good value, especially when you can get it when they offer free shipping or reduced shipping ($8.95 for 45lbs). Your calculations for the number of refills for resin depot seem more on track than what I posted.

[Origami]

The thing that I don't know, Dave, is if all mixed bed resins are created equally. I suspect that, because there are so many different types, that's not the case. You have to, in part, be aware that ion-exchange resins actually exchange one ion for another when binding the "bad stuff" in our water. What the bad stuff is being swapped out with needs to something that you're aware of. Sometimes it will be Hydrogen and Hydroxide, other times it will be sodium and chloride. Sometimes it might be something else. For our purposes, you probably want a mixed bed resin that swaps out for H+ and OH- (the "ionic form" in Resintech's data sheets).

 

The two most commonly referred to resins that I've seen on the reef sites are the NRW37 (non-indicating) and the MBD30 (indicating).

 

It may be a nit, but you may want to compare capacity if you're going to compare value - that is cost/ionic capacity. ResinDepot had some pretty decent data sheets showing their mix ratios and capacity for both anion and cation components, but your Costco link did nothing in this regard. This is going to be key to determining value.

 

For example, the ResinDepot NRW37 datasheet shows that 1 liter of the resin has a cation capacity of 1.8 equivalents, and anion capacity of 1.1 equivalents. Similarly, the ResinTech MBD-30 datasheet shows a cation capacity of 1.9 equivalents and anion capacity of 1.25 equivalents per liter - a 5% increase (or value added) for the MBD-30 if accurate.

[DaveS]

Yes I agree Tom. I k ow there a few unknowns. I figure the first thing we could do is compare simply by cost per volume. If that number didn't pass the value test, it's unlikely to be worth moving further. Your diligent research (no surprise there) showed that the Costco option is $5.36 a refill (shipping included in price) as opposed to BRS refill cost of $7.33+shipping. Resindepot is just around the middle mark at $6.64.

 

So just by volume the Costco option is about 1/3 less than BRS. That seems pretty good so maybe it's worth searching further into exchange capacity and exchange type. The Costco offering does seem to provide some detail on expo change capacity. 2 bags will treat 80,000 ppm before expiring. Wonder if there is any data put there on how much the other types will handle.

[hypertech]

How much water are you guys making that that cost difference is going to be worth the trouble? Even if the percentage is 33%, its only a savings of $2. I have to change my resin only once or twice a year.

[Origami]

Wonder if there is any data put there on how much the other types will handle.

Yes. But remember, the 80,000 figure that you have is for a certain charge size (weight). The ResinDepot data showed two factors that go to this. The first is the ratio of cation and anion resins. Without looking back, I believe it was 60/40 - could have been 40/60. The second factor is the equivalents per liter of resin. An equivalent is 6.022*10^23 (Avogadro's number) of electrons. First, you have to do the math to figure out a new capacity per liter for the mixed bed resin.... There's more math behind this, Dave and I've got guests coming for dinner in 15 minutes so I can't walk through it. Buy, using Avogadro's number, and knowing the weight of the Costco-sourced resin, you can probably figure it out. I'll try to come back to this later if I can sort it out in my head....

[hypertech]

Avacado's number is very big .......

 

I'll pay two dollars so I don't have to think that hard.....

[zygote2k]

Avacado's number is very big .......

 

I'll pay two dollars so I don't have to think that hard.....

+1

[DaveS]

How much water are you guys making that that cost difference is going to be worth the trouble? Even if the percentage is 33%, its only a savings of $2. I have to change my resin only once or twice a year.

 

Eh, sometimes is not just about the amount saved but also just the fun of learning and/or finding alternatives for what is considered the norm. I know I've learned more about DI resin through this process and Tom can demonstrate his wonderful technical skills that many knows he has.

 

I think just about everyone on this forum has a learning and DIY streak to them. Otherwise they'd just go to the LFS or hire a maintenance company. People are free to participate in this thread or not.

 

Avacado's number is very big .......

 

Hmmm, suddenly I'm hungry for LOTS of Mexican food....

Edited July 7, 2012 by DaveS

[Origami]

Avogadro, guys. Not avocado. LOL.

 

You do realize, Dave, that you guys have me digging back in my old chemistry memory banks, don't you?

 

High school chemistry taught us that Avogadro's number is the number of atoms in a 1 mole of an element. Similarly, an equivalent is a "mole" of charge. For an ion of valence (charge) +/- 1, there's 6.022*10^23 ions per equivalent. For an ion of valence +/-2, there's 3.011*10^23 ions per equivalent since each ion has a charge of two. The calcium atom, when ionized has a charge of 2. Thus, there's half as many ions in an equivalent. That's why, while a mole of Calcium Carbonate weighs 100 grams, an equivalent weighs half that, or 50 grams.

 

DI resin works by ion exchange. To pick up a "dissolved solid" - that is, an ion that you want to get rid of (say, a calcium ion) - the calcium ion trades places with another on the resin that has less affinity for the resin. This is a charge-moderated activity. So, for a resin that starts with an ionic form using H+ (hydrogen ion), when the target calcium ion (with a charge of +2) wanders by the resin, two H+ ions will be released into the water and the calcium ion will be bound. The ions are bound only so long as other ions of greater affinity don't wash by. This, by the way, is why we want to be sure to replace our depleted resin. Because, if you continue to run water with TDS through depleted resin, ionic pollutants that you got rid of earlier are released back into the output stream as ions with greater affinity trade out with those with less affinity.

 

I believe that RHF wrote an article on how this works a while back.

 

Now, to the math.

 

Let's start with the Costco setup and first assume that the mixed resin bed comes charged with H+ and OH- ionic forms. That is, let's assume that it will work for us and not give us slightly salted water as an Na+ and Cl- resin would give us. Let's use their description that shows that a single charge (2 bags of resin) will treat 1600 gallons (6056.656 liters) of 50 ppm water (18 grams per mole). Assuming a water temperature of 77 F (density 0.9970479 kg/l), we have a starting weight of 6038.78 kg of impure water. Nominally, that's 335,487.56 moles of H20. Multiplying by 50 ppm (50*10^-6), that gives me 16.774 equivalents of capacity in the two double-big-blue cartridges. Now, we need to figure out how much resin (in liters) is contained in those the two canisters. If I use BRS' guideline of 8.75 pounds in each, we have a total resin weight of 17.5 pounds. Now, assuming 45# per cubic foot, we arrive at 0.3888 cubic feet (or 11.02 liters) in the two canisters. Divide 16.774 equivalents by 11.02, and you arrive at 1.52 equivalents per liter. This is the approximate capacity of the Costco-sourced mixed-bed resin.

 

Next, we want to compare that with the NRW37 resin. The data sheet for that product indicates that it's a 40/60 cation/anion mix. The cation material's capacity is 1.8 eq/liter and the anion material's capacity is 1.1 eq/liter. Mathematically, the mixed bed resin should have a capacity of (0.4*1.8 + 0.6*1.1 =) 1.38 equivalents per liter.

 

Now, let's figure the capacity of ResinTech MBD-30. It's a 1:1 mix of 1.9 eq/l and 1.25 eq/l resins. Therefore, the mixed bed capacity is 1.575 equivalents per liter.

 

The math says the MBD-30 is superior (by a little) to both, but I'm more likely to consider this within the error tolerance of the estimates used across this analysis. That is, consider all as equal in terms of capacity by volume. By this standard, the Costco resin is a good value.

 

However, Dave, (this is a big however) not all resins are created equally. Not only do you have to be concerned with the lack of information about the ionic form of the resin, you also have to consider the lack of information about impurities in the resin that may leach out during use. It's that uncertainty that would give me pause. It may be fine stuff, but without specification or some guarantee on the resin grade, you may be playing Russian roulette. After all, a car doesn't care if it's exposed to a few impurities leaching out of resin. Our tanks may, though. Again, I'm not knowledgeable on resin quality control, so this may be an unfounded concern that requires more research.

 

Out of curiosity, I wonder what kind of deal we could get on a group buy of resin? I suspect that, while the color changing resin is more expensive, there are more people using it. What would be the minimum size order to get a decent discount and what supplies and equipment would we need to re-package resin into smaller, usable vacuum-sealed packages?

[Origami]

Here's the RHF article that I eluded to above. This link takes you directly to the section describing how DI resin works. The section just afterwards warns of what happens when resin is used after depletion.