I need to know the conversions and formulas for a class/inservice I am giving on Water Softeners

Are you asking about calculating how many grains of hardness a tank would remove, how often to regenerate and how much salt to use per regeneration?

It was a simple question!! I take my job of taken care of the patients and responsibility very serious.

I know that:

1. 1 cu. ft of softener resin removes 30,000 grains
2. 1 gpg = 17.2 ppm
3. To convert ppm to gpg you have to multiply ppm by 0.058
4. To convert gpg to ppm you have to divide gpg by 0.058
5. mg/l = ppm
6. Softener must be sized for at least 1 full days operation
7. I know that(Perm flow + Reject flow x 60 min x hours of operation) will let you know how many gallons of water is used per day

Just thought I could get some ideas from others

Thanks

Couple of other issues to consider:
If carbon tanks are downstream of softener, the carbon backflush (nightly?) will also use softened water (@ 20 - 30 gpm) and will affect softener capacity

Also, 30000 grains per cu ft of resin assumes new resin. As the softener ages, the resin gradually loses capacity, surface area, compaction,etc. so better to plan some safety margin as 30000 grains per cu ft is "best case" performance

1. A cubic foot of resin has a new capacity of 45,000 grains. At a 15 pound of salt dosage, 30,000 grains will be recovered. 10 lb = 25,000 grain and 5 = 20,000 grains. 45K can be achieved using a 60 lb dosage and extended dwell time. Not really worth it.
2. Actually, gpg = 17.1 ppm of hardness elements. Needless to say, Sodium doesn't count. A water analysis of the incoming is helpful.

Sizing a softener is always best to go a little over and not scrimp. Knowing that 2 ppm of calcium is the limit, with 200 ppm of calcium (11.6 gpg (ppm/17.1)I find it easier or gpg X 17.1 just one number to remember) coming out of an exhausted softener the RO would have to be at 99% rejection to even be close. The reason to check the hardness at the end of the day.

As another note, if you have to bypass the RO and go on straight DI, always bypass the softener. Sodium is a weak (single positive charge ion) and cation resin doesn't exchange it well. Sodium plus Hydroxide from the anion bead is NaOH and degrades the water quality even though the resin isn't really exhausted. Bypass the softener to achieve longer run time on the DI and higher water quality.

Just my thoughts
Take care
Life is GOOD!!!

Willie B.,

Could you give some references and back-up data for your suggestion to by-pass the softener when running on straight D.I.? We have a few facilities that occasionally have to run on D.I. and any legitimate means to extend the life of the D.I. would be helpful. Anyone else? Florian?

Willie is way on point....The science behind it is pretty simple....bypassing the water softener will help the DI last longer.Removing Calcium and Magneseum is much easier for the DI to remove than loading them up with sodium from the ion exchange process going on in the softener.

Mark, bypassing the softener does not make a big difference. The Softener will remove Ca and Mg but it will replace it with an equivalent amount of sodium. The Ca and Mg will take up as much capacity in the DI as would the Na. Willie is correct in that DI does remove Ca and Mg better than Na. You may get a little better water quality by bypassing the softener, but you shoud not notice any additional length of operation.

If you bypass the softener and you have Cation and Anion beds, it is important to put the Cation bed first, followed by the Anion, with a Mixed bed at the end.

If you run on DI, make sure you have a good ultrafilter after the DI.

I disagree with Florian on this one. Hydrogen has a single positive charge and so does Sodium. The very reason that Sodium is used as the exchange ion for a water softener. Why should the cation bead give up Hydrogen to take on Sodium when it is totally content with what it has. Sodium leakage has always been a problem with DI and always the first ion through the bed. Softener resin is cation in the sodium state. To turn it into DI use, you would have to go 3 or 4 times the normal acid dosage or overwhelm it with Hydrogen to even think about bringing the Sodium off. I have been on many calls over the years where the DI is showing exhaustion on softenened water. We bypassed the softener, flushed the DI and quality was returned and many gallons of water was delivered. Trust this one. Bypass your softener and in most cases you will get 3 times the capacity. I'll pull my Rohm and Haas manual out tonight and see what I find on Sodium removal using DI. I know it's not in their application scheme.

Take Care
Life is GOOD!!!

Clash of the Titans; I love it!

I spoke with one of our techs that uses DI and her experience is that the DI last longer when she leaves the softener on line. The science does not seem to be validated by the practical experience. Let the debate continue. It would be nice to get a semi, quasi, in-official national poll to see what others have experienced. My prediction: the science will be roughly balanced and the practical experience will be mixed; but at least we will make an informed decision of which path to take.

I seem to recall Larry posting an explaination about this in the past but I can't find it. If I recall correctly, even if two things have the same charge, one is going to be a stronger bond than the other.

Chuck

Cation resin does selectively remove some ions better than others. Generally, it removed trivalent ions (+3) better than divalent ions (+2) better than monovalent ions (+1). But, the resin also selects some monovalent ions over other monovalent ions. Softener resin likes calcium (+2) ions over Magnesium ions (+2), it likes Magnesium ions over Potassium (+1) ions. It likes Potassium ions over sodium ions (+1). And, for DI systems, it is very well documented that it likes sodium ions over hydrogen ions (+1).

If you believe bypassing the softener is better for you, that's fine. If you believe leaving the softener online is better for you, that's fine. Neither option will cause a problem.

Goodness, what a great thread! I was impressed by someone sometime ago (who I believed) that it is always better to bypass the Softener when running Deionization Bed Tanks. Now that it is plainly demonstrated in this thread that it is of no conseqence one way or the other, I would opt for the KISS rule...leave the Softener on line. Life is already complicated enough when your RO is sick.