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Can a water softener replace DI?


Mudfish

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We have well water at our house, with a fancy water softener. I was talking to the guy who comes out and services the well system, about my plans to install a RO/DI filter.

 

Says he: "Why would you need the DI part? That's what a water softener does, is deionization. Seems to me, all you need is RO."

 

He said that all of his customers that have aquariums, that also have water softeners, use only reverse osmosis filters to make their aquarium water. While he admittedly doesn't know squat about reefkeeping, he is really knowledgeable about potable water systems.

 

Could he be right? Is there any truth to this?

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I would think if you take your water and put it through RO filtration, you have pure water ready for an aquarium. I don't think all that use RO water in a reef also filtrer it though a DI system.

 

The water to be treated passes through a bed of the resin. Negatively-charged resins absorb and bind metal ions, which are positively charged. The resins initially contain univalent hydrogen, sodium or potassium ions, which exchange with divalent calcium and magnesium ions in the water. This exchange eliminates precipitation and soap scum formation. As the water passes through both kinds of resin, the hardness ions replace the hydrogen, sodium or potassium ions which are released into the water. The "harder" the water, the more hydrogen, sodium or potassium ions are released from the resin and into the water.

 

http://en.wikipedia.org/wiki/Water_softener

Edited by StevieT
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water softeners are not completely good. they only add sodium to the water and taking out calcium and other heavy metals. the only water softener that actually removes elements from the water without adding elements is the HAGUE water softeners. if you have that, most people would still recommend RO.

 

 

use potassium not sodium in you softener, its more expensive, but does a better job.

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water softeners are not RO filters!!!!

 

Quick tutorial that points out the differences:

water softeners change the water by adding sodium chloride (or another substance)to the water. It "softens" the water by displacing the calcium and magnesium (which cause hard water), with an ion that does not cause hard water. This allows soap and detergent to make better suds/foam. It does not remove any of the ions that are bad for our fishtanks (nitrate, phosphate, sulfide, etc.)

 

where RO passes the water through a membrane that has holes only big enough for water, but not the ions. This removes most of the ions, good and bad, from the water. Then you need to add back the good ions (sodium, chloride, calcium, magnesium, carbonate, iodide, etc = SALT).

 

DI takes the water that is MOSTLY free of ions (from the RO) and switches the last few ions with either H+ (hydrogen ions = acid) or OH- (hydroxide ions = base). Then the H+ and the OH- ions combine to make H2O (water). Leaving extremely pure water.

 

If you use a TDS (total dissolved solids) meter for your water before and after a water softener, the water will have MORE TDS after the softener. On RO water, there is usually almost zero TDS after. After just using a DI unit, there is usually almost zero TDS (a little higher than using RO water), and after using a RODI unit, there is usually zero (or 0.001) TDS reading.

 

I hope that this did not get too technical.

dsoz

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water softeners are not RO filters!!!!

 

Quick tutorial that points out the differences:

water softeners change the water by adding sodium chloride (or another substance)to the water. It "softens" the water by displacing the calcium and magnesium (which cause hard water), with an ion that does not cause hard water. This allows soap and detergent to make better suds/foam. It does not remove any of the ions that are bad for our fishtanks (nitrate, phosphate, sulfide, etc.)

 

where RO passes the water through a membrane that has holes only big enough for water, but not the ions. This removes most of the ions, good and bad, from the water. Then you need to add back the good ions (sodium, chloride, calcium, magnesium, carbonate, iodide, etc = SALT).

 

DI takes the water that is MOSTLY free of ions (from the RO) and switches the last few ions with either H+ (hydrogen ions = acid) or OH- (hydroxide ions = base). Then the H+ and the OH- ions combine to make H2O (water). Leaving extremely pure water.

 

If you use a TDS (total dissolved solids) meter for your water before and after a water softener, the water will have MORE TDS after the softener. On RO water, there is usually almost zero TDS after. After just using a DI unit, there is usually almost zero TDS (a little higher than using RO water), and after using a RODI unit, there is usually zero (or 0.001) TDS reading.

 

I hope that this did not get too technical.

dsoz

awww come on man, i just said that. ill take pictures of my hague softener though. it works just as well as RO. hague is the only softener on the market that takes out phosphates and nitrates and all that bs.

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I don't think the OP or anyone else here, well maybe Abe, thought that a water softener was a RO filter.

 

They were asking if the softener was a DI filter, then he would run that water through a RO filter and add to his aquarium.

Edited by StevieT
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I don't think the OP or anyone else here, well maybe Abe, thought that a water softener was a RO filter.

 

They were asking if the softener was a DI filter, then he would run that water through a RO filter and add to his aquarium.

oh crap. i thought he said if it could replace RO. well, i dont know the mechanics to DI, so i cant help you.

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oh crap. i thought he said if it could replace RO. well, i dont know the mechanics to DI, so i cant help you.

 

 

I read it as

 

water from softener ---> ro filtration ----> aquarium (happy fishies)

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I don't think the OP or anyone else here, well maybe Abe, thought that a water softener was a RO filter.

 

They were asking if the softener was a DI filter, then he would run that water through a RO filter and add to his aquarium.

Thank you. *sigh* Maybe I wasn't clear. I'll try again.

 

Can a water softener and an RO unit replace an RO/DI unit?

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So, your guy says water softeners & DI are the same? He's wrong.

 

 

As for the system, you don't really need DI with RO, but it does help finish off whatever RO lets through and gets you closer or at 0.0 TDS.

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I can't really answer your question. However, I recently got a Typhoon III RO/DI unit and that thing spits out water with 0 TDS. A couple of weeks knocked out a major hair algae problem and all my corals look better.

 

Perhaps you don't need one, but it is really great to have IMO.

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Just tossing in my .02 cents worth having previously worked for a water treatment company that sold RO's, Softeners, Iron Systems (wells) and worked in that industry for a few years.....

 

I don't necessarily agree that Hague systems are the only ones that don't add sodium to the water. The DI crystals in any water softener get flushed with a brine solution. Think of DI crystals as golf balls. The divets in the DI crystals collect the hardness (minerals and other goodies) in the water and eventually need to be freed of these things. That's why it flushes with salt (or potassium). It cleans and recharges the DI crystals. After flushing the DI crystals with brine, the systems usually take fresh water and cleans and flushes that brine solution out of the DI bed. Some systems may flush better than others, and quite honestly, some systems allow you to adjust the length of time that the system flushes that brine out, thus helping to reduce the sodium/potassium. You may want to see, if you're concerned about sodium, if yours allows you to adjust the flush time.

 

I had a system in my home in Charleston and I found myself having to buff the water a tad bit more, but not enough to sway me from keeping it.

 

If you're adding an RO after the softener, in theory, I believe it would remove any added sodium from the water that a softener would have added as a result of the flushing process...but obviously the type of RO you have would play a part in that I believe.

 

Out of curiosity...what brand softener is it?

 

</soapbox>

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So, your guy says water softeners & DI are the same? He's wrong.

 

I believe the crystals he's referring to are the same. There are better brands or designs than others, but overall they are the same. I think it's important to note difference here...

 

DI filters on an RO are placed inline after the water passes through the membrane. The TDS meter prior to the water entering the DI filter(s) after passing the RO Membrane (depending on the TDS readings going into RO of course) should be minimal. VERY minimal. The DI filters can then 'finish it off' and take the last little bit of stuff out of the water.

 

In a whole house system, the water may read 75, 100, 200, 300 on a TDS meter before going into a softener. Because of the high levels of stuff in the water, the crystals get used up faster. Then the system will need to be flushed at a different frequency than someone in another area...

 

I think the big difference between Softeners/DI is just the flushing process. We just replace the DI crystals in our RO/DI where as a whole house system just flushes and reuses the same crystals.

 

The DI in an RO/DI system lasts a while because the water has gone through a membrane. In the case of the OP, I think one thing to note is he'll find that his RO wears out alot less if water is going through his softener first.

 

One other thing to note...Chlorine can destroy ION crystals too btw. I've rebedded systems and had to remove the old DI stuff. It is almost as if the crystals are melted, and all broken down. Quite gross actually. Most areas over treat the water with Chlorine. If you ARE using a softener, and have no carbon filter to assist in removing the the Chlorine, then your ION exchange crystals will not last as long and have to be rebedded.

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  • 2 months later...
BuckeyeFieldSupply

Let's backup a little.

 

A water softener is similar to, but not the same as a DI water purification system. What we all talk about as "DI resin" is better referred to as a mixed-bed resin. That is, it contains "anion beads" and "cation beads" that serve to remove from the water anions and cations - that is, any particals with an electrical charge (at a molecular level), and replace them with H+ and OH- that join and make...pure water. .

 

If you opened up a water softener, what you'd find is a different type of DI resin. It is a cation (only) resin. It exchanges sodium+ ions for other cations in the water - most typically calcium and magnesium. It is these two substances in water that make water "hard."

 

So in answer to your question, no - a water softener does not replace a DI stage. A water softener does however provide benefits in treating water fed to an RO system. The calcium and magnesium (that the softener removes) are responsible for that build up of menerals on faucets, showerheads, etc. These deposits, called "scale" also tend to build up inside an RO membrane. Softened water eliminates this issue.

 

So if you have a softener, your water purification system should look like this:

 

SOFTENER -> SEDIMENT FILTER -> CARBON BLOCK -> RO MEMBRANE -> DI RESIN STAGE

 

Russ @ BFS

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SOFTENER -> SEDIMENT FILTER -> CARBON BLOCK -> RO MEMBRANE -> DI RESIN STAGE

Don't forget to have a sediment filter before the softner on a well fed system and a good sediment/carbon filter on a municipal fed supply that has chlorine added to the water.

 

If you're adding an RO after the softener, in theory, I believe it would remove any added sodium from the water that a softener would have added as a result of the flushing process...but obviously the type of RO you have would play a part in that I believe.

Yes, the RO unit will remove the sodium or potassium

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chvynva916

If I were you, instead of trying to determine what my particular water softener was doing to my water and whether it was producing good reef-quality water (which in the end will involve some speculation) I would just test the water with a TDS meter. Whatever method you're proposing, if the TDS meter reads sufficiently low, you're probably safe. If it doesn't, I'd worry about what those "TDS" are.

 

In the end, RO/DI isn't that much more expensive than RO, which you're proposing to use in conjunction with your water softener. I say save yourself the concern and just go RO/DI. May or may not be necessary, but it's one less thing to worry about.

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BustytheSnowMaam

I would say your water softener man is right- I forwarded your question to my husband at work to see what he thought. That is exactly what a water softener does- deionizes. However, I would be uncomfortable using RO water, because RO water is stripped of everything and therefore is very aggressive- it will readily leach copper and metals from your pipes. I think that having the water softener will make your water perfectly safe to use and you don't need either an RO unit or RO/DI unit. Again, I forwarded your question to my husband both for my own edification and to get a good scientific answer.

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chuckfullservice

I'm not quite understanding why you would need DI after running your water thru and RO ? If RO removes almost all TDS down to.0001 why would you need the softener before running it thru the RO wouldn't that kind of be senseless since the RO unit is going to remove the calcium and other solids ie salts minerals that you just added with the softener and any bad minerals copper ect...?

Why not just use R.O. Then add salt mix and your done ???

Edited by chuckfullservice
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However, I would be uncomfortable using RO water, because RO water is stripped of everything and therefore is very aggressive- it will readily leach copper and metals from your pipes

 

That is true. But it isn't a problem unless you are running a whole house RO system through your copper pipes. That method is best used with PVC piping throughout the house. I can't think of any metal parts of my setup that touch the water. Also when you add the salt mix to the water, the water is no longer hungry.

 

You are best off adding a RO/DI or distilling system. Less chance of adding unwanted "impurities" like nitrates and phosphates. A softener by itself will not remove them. It will only correct hardness. Since the source is a well, there could also be more contaminants that only a seperate system could take out.

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BustytheSnowMaam

This was my husband's response, I don't know if it explains anything really:

 

"Without knowing the quality of the "raw" well water I can't give a 100% sure answer. However, I would venture to say the RO unit alone would be just fine. The RO will remove just about everything pushed through the "membrane". The DI unit would remove the 1% of the stuff the RO unit missed due to imperfections in the membrane and other "leaks".

 

A DI unit alone doesn't produce absolutely pure water, it is convenient and quick, and may be sufficient for many applications. It is an excellent system for removing dissolved solids and gases, although it has a generally poor rating for other impurities.

 

A RO unit followed by a DI unit produces 99.9% pure water.

 

With the RO unit alone, the water produced will be amost pure, meaning there are no good things in the water such as calcium, magnesium, and other minerals found in natural sea water.

 

Something else to consider is stagnant water in the DI cartridges can actually encourage the growth of bacteria."

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