What's the Point in RO/DI, then?

[mark.nicodemus59]

After 4 years of dealing with algae blooms and invertebrate deaths, I learned that my problem may not be rooted in "operator error" but in the local water supply and the idea that conditioner really works, I finally realized how critical RO/DI water is to a reef setup.

Not surprisingly, then, I was thrilled to learn that a local store has a vending system from which I can buy RO/DI water at only 25¢ per gallon. I bought some good food grade 5-gallon containers, and went for a quick supply, but when I got back from the store and tested the water, it metered at 11 TDS.

I Googled this unexpected result, and verified that RO/DI water should test out at 0 TDS--anything above that is unsuitable for reefing. It was the clearest water I'd ever poured down the drain.

I spoke with the people I trust at my LFS, and after telling them the story, they agreed that I'd made the right choice by disposing of the batch from the vending machine, and explained in great detail what had likely gone wrong--DI resin exhaustion. They all seemed to think it was odd that I had trusted what they knew to be a totally unreliable source.

So I asked, "Do you guys sell RO/DI water and premixed saltwater?"

Short answer: YES.

I happily brought my containers in and had them fill them from their trusted RO/DI system for my planned water change, and then paid them the $1/gallon fee, but when I got home and tested the water, it registered 12 TDS!

The LFS had already closed for the day, but I sent a quick e-mail and got a call the following morning. They had found the problem and fixed the system, so I could return to the store and get the water replaced.

When I arrived at the store, I was met by the owner, who explained to me that 12 TDS is perfectly acceptable, that they use water of that quality in their system, and that he never even considers changing filters, membranes, or resin until the water gets to 10 TDS!

I had them replace the water anyway, and afterward was charged for the replacement.

I dug deep into the standards of the community and profession. You never hear or read anything that low enough is close enough!

What's the point, then?

 

[Chris_from_SoCal]

Instead of relying on RO water from someone that you have not idea on how often they change the filters or do maintenance why not install your own system. They do not cost that much to purchase and will save you way more in the long run.

 

[mark.nicodemus59]

Instead of relying on RO water from someone that you have not idea on how often they change the filters or do maintenance why not install your own system. They do not cost that much to purchase and will save you way more in the long run.

Actually in the works right now. A Neptune 8-Stage system. I made that decision as soon as I got home from my "trusted" LFS.

 

[fish_collector]

That’s typical of LFS RODI. However if you just dunked the sensor of an HM unit into the bucket to get your reading that may not be accurate. I’ve had similar results and found unless it is in the flow of water it’s not accurate. A Hanna com100 can give you accurate readings by just putting it into a bucket of water though, but much more spendy.

 

[fish_collector]

You can build your own very affordably as well. I’d suggest only using a Filmtek 75gpd membrane and virgin resins, BRS sells high quality resins, anion, cation and then mixed bed.

 

[Chris_from_SoCal]

I recently installed a 200GPD unit in my garage. One line runs local so I can fill a large clean trash can for salt water changes and another that runs through the attic to the aquarium where I can direct fill or use it for an ATO system.

 

[mark.nicodemus59]

You can build your own very affordably as well. I’d suggest only using a Filmtek 75gpd membrane and virgin resins, BRS sells high quality resins, anion, cation and then mixed bed.

Thanks! I'll look into that option.

 

[mark.nicodemus59]

That’s typical of LFS RODI. However if you just dunked the sensor of an HM unit into the bucket to get your reading that may not be accurate. I’ve had similar results and found unless it is in the flow of water it’s not accurate. A Hanna com100 can give you accurate readings by just putting it into a bucket of water though, but much more spendy.

I always worry about that as well. I always check the calibration of my meter by first checking a sample of distilled water, which always tests out at 0 TDS (so far).

 

[mark.nicodemus59]

I recently installed a 200GPD unit in my garage. One line runs local so I can fill a large clean trash can for salt water changes and another that runs through the attic to the aquarium where I can direct fill or use it for an ATO system.

Nice! How's it working for you?

 

[Project1004]

Good idea on making your own RODI water.

I’m suppose to change out the 6filters (it’s 7stage RODI) every 6month (even though i have small tanks). I havnt got new filters yet though. I’m stretching it this time. I’m using boost pump due to low water pressure. And it’s showing tds of 2 coming into first portion of the unit which I am not sure which is. -.-

PS: We can drink RO water but not the RODI water. It’s not good for consumption.

 

[Buckeye Hydro Verified Sponsor]

As someone mentioned above, don't expect accurate readings if you dip your tds meter in a reservoir full of DI water. Remember that you are reading in parts per million... so the slightest bit of "dirt" will change the reading. You can change the reading by putting your finger in a glass of DI water.

In general, TDS meters are very robust. Unlike pH meters they keep their calibration well, and there's little need to spend big bucks on a TDS meter.

Don't fall into the trap of thinking "more stages = better filtration." Four stages is a good default configuration for most people in this hobby.

 

[JumboShrimp]

OP @mark.nicodemus59 , thanks for sharing your experience/nice write-up. I think you'll be more satisfied when you start making your own RO/DI... as it probably follows the old adage, "if you want something done right, do it yourself." Best wishes!

 

[Paul B]

When I arrived at the store, I was met by the owner, who explained to me that 12 TDS is perfectly acceptable,

I also feel that 12 is fine. My tap water is about 160. We have well water here and that is mostly iron, calcium and probably some insecticide, fertilizer, DDT, napalm and maybe Coca Cola.

But in such small amounts that it won't hurt anything and heck, maybe even be beneficial. Who knows.

Mine comes out at zero or one but I used New York City tap water for years until one day I almost killed everything because the city put Zinc orthophosphate in the water to control corrosion in the pipes.

Besides that, it is fine.
In other words, no one really knows. (but zero is probably better)

 

[Randy Holmes-Farley Verified Community Expert]

When I arrived at the store, I was met by the owner, who explained to me that 12 TDS is perfectly acceptable, that they use water of that quality in their system, and that he never even considers changing filters, membranes, or resin until the water gets to 10 TDS!

I had them replace the water anyway, and afterward was charged for the replacement.

I dug deep into the standards of the community and profession. You never hear or read anything that low enough is close enough!

What's the point, then?

First, I'd point out that at Reef2Reef there are literally hundreds of threads talking about TDS and what targets should be for an RO/DI system.


Second, TDS itself does not matter at all. It entirely depends on what chemicals make up that TDS. FOlks need to be concerned about copper, phosphate, silicate, ammonia, chloramine, nitrate, etc.

Folks need not be concerned about sodium, calcium, chloride, magnesium etc.

Ensuring the TDS is 0 ppm totally ensures that there are not problematic levels of anything. Higher levels of TDS may be fine (or not), but one either determines it is fine by trial and error or ICP-MS testing of the output water.

For example, I've used RO/DI for several decades. BUt I'm considering switching to RO only to save money. My system takes 99 ppm TDs tap to 8 ppm TDS after the RO membrane and 0 after the DI. I'm planning to test the 8 ppm TDS water to see if it is suitable to save money on DI resins.

 

[Buckeye Hydro Verified Sponsor]

First, I'd point out that at Reef2Reef there are literally hundreds of threads talking about TDS and what targets should be for an RO/DI system.


Second, TDS itself does not matter at all. It entirely depends on what chemicals make up that TDS. FOlks need to be concerned about copper, phosphate, silicate, ammonia, chloramine, nitrate, etc.

Folks need not be concerned about sodium, calcium, chloride, magnesium etc.

Ensuring the TDS is 0 ppm totally ensures that there are not problematic levels of anything. Higher levels of TDS may be fine (or not), but one either determines it is fine by trial and error or ICP-MS testing of the output water.

For example, I've used RO/DI for several decades. BUt I'm considering switching to RO only to save money. My system takes 99 ppm TDs tap to 8 ppm TDS after the RO membrane and 0 after the DI. I'm planning to test the 8 ppm TDS water to see if it is suitable to save money on DI resins.

Agreed.

Also - a ~92% rejection rate isn't great. You should be able to get that RO TDS down w/o too much trouble/expense.

 

[mark.nicodemus59]

When I arrived at the store, I was met by the owner, who explained to me that 12 TDS is perfectly acceptable,

I also feel that 12 is fine. My tap water is about 160. We have well water here and that is mostly iron, calcium and probably some insecticide, fertilizer, DDT, napalm and maybe Coca Cola.

But in such small amounts that it won't hurt anything and heck, maybe even be beneficial. Who knows.

Mine comes out at zero or one but I used New York City tap water for years until one day I almost killed everything because the city put Zinc orthophosphate in the water to control corrosion in the pipes.

Besides that, it is fine.
In other words, no one really knows. (but zero is probably better)

Thanks for this! As I said, in the industry it's touted as ALL OR NONE. Either it's zero TDS, or it's unusable. The issue I've been handed most is that the DI stage removes ions, and if that stage is getting close to being exhausted, there's no way to see WHICH ions are getting through.

My local water metered at 501, and that includes a copper content of 1.3ppm (lethal level for inverts). This is my new paranoia.

It's likely that the all-or-none campaign is propaganda started by producers and suppliers or RO/DI systems, but after losing so many inverts over the past few years, I'm just being cautious.

Please! If anyone else agrees that relatively low TDS levels are acceptable, speak out! I value truth over hype!

 

[BeanAnimal]

Your buckets almost certainly contributed to the reading as well. My reef is decades old. I have gone years running with exhausted resin and filters, arguably dumping TDS from the exhausted resin back into the output. I have no outright issues that I can attribute to water quality. They may be there, I don't know.

My water and your water are not the same, but the point is that 0 TDS is not something that I have ever worried about.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for this! As I said, in the industry it's touted as ALL OR NONE. Either it's zero TDS, or it's unusable. The issue I've been handed most is that the DI stage removes ions, and if that stage is getting close to being exhausted, there's no way to see WHICH ions are getting through.

My local water metered at 501, and that includes a copper content of 1.3ppm (lethal level for inverts). This is my new paranoia.

It's likely that the all-or-none campaign is propaganda started by producers and suppliers or RO/DI systems, but after losing so many inverts over the past few years, I'm just being cautious.

Please! If anyone else agrees that relatively low TDS levels are acceptable, speak out! I value truth over hype!

I think you are missing some critical points and some things you claim are industry propaganda are simple facts. It seems like you are looking for a blanket ok on, say, 2 ppm tds and that is false.

 

[mark.nicodemus59]

Thanks for this! As I said, in the industry it's touted as ALL OR NONE. Either it's zero TDS, or it's unusable. The issue I've been handed most is that the DI stage removes ions, and if that stage is getting close to being exhausted, there's no way to see WHICH ions are getting through.

My local water metered at 501, and that includes a copper content of 1.3ppm (lethal level for inverts). This is my new paranoia.

It's likely that the all-or-none campaign is propaganda started by producers and suppliers or RO/DI systems, but after losing so many inverts over the past few years, I'm just being cautious.

Please! If anyone else agrees that relatively low TDS levels are acceptable, speak out! I value truth over hype!

I think you are missing some critical points and some things you claim are industry propaganda are simple facts. It seems like you are looking for a blanket ok on, say, 2 ppm tds and that is false.

Thanks for calling this out. Truth is, I'm not looking for approval on using water above 0 TDS. I want to know what others are experiencing. If 0 TDS is required, I believe we need to hold LFSs accountable for selling bad water and then claiming that a little TDS is acceptable. I'm upset that they sold me water that by industry standards is unacceptable and then charged me to replace it when I complained.

 

[mark.nicodemus59]

Your buckets almost certainly contributed to the reading as well. My reef is decades old. I have gone years running with exhausted resin and filters, arguably dumping TDS from the exhausted resin back into the output. I have no outright issues that I can attribute to water quality. They may be there, I don't know.

My water and your water are not the same, but the point is that 0 TDS is not something that I have ever worried about.

Thanks for dropping this in. I agree. Not all ions or particulates are harmful, but in my area, our water supply is high in copper, barium, and antimony. Though it isn't reported, we also have a lot of agricultural drain off, which I am told contributes to my astronomical phosphate and nitrate levels.

The LFS has sold me a virtual pharmacopeia of chems to deal with the issue, but with absolutely no success! It was only a little over a month ago that I was enlightened about the water supply. The annual report was crushing.