Dockside Chat - Water Filtration Specialists... Need your help

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ThreeLittleFish
03-28-2012, 11:20 AM
I have a portable water de-ionizer I use at the marina to rinse my boat after washing. We have very hard water at my marina. The marina installed a water softener to remove the minerals. Obviously a water softener exchanges the mineral ions for sodium ions so we are left with a good deal of salt in the water that's creating spots. I have separate cation and a anioin chambers. Do I need both or will either just the cation or anion remove the salt. I'd hate to waste the money on changing both resins if only one is removing the salt. It get's expensive. Which one removes the sodium?


TheRealMacGyver
03-28-2012, 07:43 PM
Maybe I'm ignorant, but a water softener uses the salt to clean the media that removes the calcium from the water source. The water that comes out of the water softener has maybe a microscopic amount more salt in it than the water would have otherwise. The salt is only used during the "backflush" period, usually ran during early morning hours. What am I missing here?

ThreeLittleFish
03-28-2012, 08:13 PM
The sodium is absorbed into the resin media in the softener. There is an ion exchange for every mineral ion that is absorbed by the resin a sodium ion is released. If your water is very hard then a lot of sodium will be released. When you recharge the resin it is exchanging the mineral ions for the sodium ions again. It's not used to backflush.

If the water entering the water softener is 350PPM then the water leaving will also be 350PPM. It does nothing to remove total dissolved solids.


DAL1955
03-28-2012, 10:03 PM
The sodium is absorbed into the resin media in the softener. There is an ion exchange for every mineral ion that is absorbed by the resin a sodium ion is released. If your water is very hard then a lot of sodium will be released. When you recharge the resin it is exchanging the mineral ions for the sodium ions again. It's not used to backflush.

If the water entering the water softener is 350PPM then the water leaving will also be 350PPM. It does nothing to remove total dissolved solids.

Sorry; You have to replace both resins in a deionizer - because the softener simply exchanges calcium and magnesium with the more soluble sodium. The exchange creates sodium sulfate and carbonate which are more soluble in water and will not scale pipes or interfere with soaps and detergents like the calcium and magnesium salts do.

Sodium is a cation + - the anionic resin in your deionizer removes it. The cationic resin removes the anions - like carbonate or sulfate. The spots you are seeing are technically not salt, as in NaCl, but the sodium salt of sulfate or carbonate which appear when the water drops evaporate. Rain will wash them away, where it will not wash away the calcium or magnesium salts of carbonate or sulfate.

DAL

DAL1955
03-28-2012, 10:05 PM
The sodium is absorbed into the resin media in the softener. There is an ion exchange for every mineral ion that is absorbed by the resin a sodium ion is released. If your water is very hard then a lot of sodium will be released. When you recharge the resin it is exchanging the mineral ions for the sodium ions again. It's not used to backflush.

If the water entering the water softener is 350PPM then the water leaving will also be 350PPM. It does nothing to remove total dissolved solids.

Just to correct a little, the resin in a softener is initially charged with sodium cations. When hard water is passed through it, the calcium in the water replaces the sodium in the water. Periodically, the resin needs new sodium to continue working, so the salt is used in the regeneration cycle to recharge the resin so it can continue working.

DAL

ThreeLittleFish
03-28-2012, 10:08 PM
Sorry; You have to replace both resins in a deionizer - because the softener simply exchanges calcium and magnesium with the more soluble sodium. The exchange creates sodium sulfate and carbonate which are more soluble in water and will not scale pipes or interfere with soaps and detergents like the calcium and magnesium salts do.

Sodium is a cation + - the anionic resin in your deionizer removes it. The cationic resin removes the anions - like carbonate or sulfate. The spots you are seeing are technically not salt, as in NaCl, but the sodium salt of sulfate or carbonate which appear when the water drops evaporate. Rain will wash them away, where it will not wash away the calcium or magnesium salts of carbonate or sulfate.

DAL

Ahhhhhh.... Thank you. Makes sense to me now. I was trying to save some money but I see that's not possible. Thanks for the explanation. I guess I have to replace both resins. I heard either the cation or anion lasts much longer than the other is that true?

DAL1955
03-28-2012, 10:25 PM
Ahhhhhh.... Thank you. Makes sense to me now. I was trying to save some money but I see that's not possible. Thanks for the explanation. I guess I have to replace both resins. I heard either the cation or anion lasts much longer than the other is that true?

Depends on how efficient the softener is and whether the resins have equivalent exchange capacity... but generally it should be about 1:1 because you are absorbing Na+2 on one resin and CO3-2 on the other. If the resin volumes are equivalent, they should last about the same amount of time assuming they have equivalent exchange capacity. You need both resins to make truly demineralized water. Exchange capacity is the measure of how many anions or cations the resin can hold per unit weight of resin.

DAL



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