Acceptable TDS for RO output water?

[nekomi]

Hi everyone,

 

I'm currently in the process of making my first batch of SW. I have a great 6-stage RO/DI system, so I hooked it up to the faucet today and started it up. I have a few questions regarding the water that it puts out.

 

1. The instructions say not to drink the first batch of RO water that the filter puts out, but rather discard it. Is this necessary for filling the tank too? Should I discard the first 5 gallons or so like the manual says?

 

2. What is an acceptable TDS reading for the output water? When I measured a small cup of output water (right after the system started up), it read 68 ppm, down from 170 ppm straight from the tap. Will it become more efficient after its been running for a few gallons?

 

Thanks!!

[Travis]

It needs to be close to 0, mine reads 2. Make sure you are testing the right line, I used the wrong line for a month before I ordered a TDS meter and realized I was using the wrong line. live and learn lol.

[Samc]

Toss the first few gallons like reconmended. Any filter system with GAC Carbon filters needs to be properly "flushed", i.e running several gallons of water throught the system and tossing it (or watering plants, definatly not tank sutiable water). And membranes need to" flushed" as well (which is the most important part). However, if possible, and your di doesn't have a carbon block after it like some systems, their is no need to run through the DI because your just wasting DI resin.

 

Optimal TD out of an RI/DI system is zero. Record after "flushing" per the directions. You should be seeing under 50 ppm after just the ro, and lower is better (around 20 is good). This is heavily dependent on on water flow, temperature and intial. You want as much flow as possible and a water temperture in the 60-70 degree F range. After the DI, you should be seeing zero or near zero (like 5).

 

Posting a link to your unit could be helpful to others as well!

[reefhog]

Before I installed my own RO/DI unit, I had been buying RO water from my LFS for a few months. When I got my RO/DI unit, I measured the last batch of RO water I bought and it was about 30ppm. My own RO/DI unit now gives me 0ppm.

 

Obviously, 0ppm is way better than 30ppm. But it doesn't mean 30ppm doesn't work. My aquarium and its inhabitants were doing fine with the 30ppm RO water. I am guessing they would be happier with 0ppm but there is no easy to tell.

[nekomi]

Thanks for all the info, guys. My system has put out about 5 gal now, and the reading is down to 10 ppm. So things are looking better! Is there any reason to toss the water if the reading is so low, or should I still discard it? I have about 50 gal to make, so I'm thinking that by the time I'm done, the 10 ppm in this 5 gal won't matter much when spread across 50 gal total... is this correct?

 

Or, is there some kind of residue from the carbon "getting flushed out" that the TDS meter can't pick up? Is this the reason for discarding?

 

Thanks again for the help... I'm glad that the system is starting to "break in" now.

[wav3form]

Thanks for all the info, guys. My system has put out about 5 gal now, and the reading is down to 10 ppm. So things are looking better! Is there any reason to toss the water if the reading is so low, or should I still discard it? I have about 50 gal to make, so I'm thinking that by the time I'm done, the 10 ppm in this 5 gal won't matter much when spread across 50 gal total... is this correct?

 

Or, is there some kind of residue from the carbon "getting flushed out" that the TDS meter can't pick up? Is this the reason for discarding?

 

Thanks again for the help... I'm glad that the system is starting to "break in" now.

 

Yours might be taking longer to break in or maybe something else is going on. I bought one of the typhoon 3 setups and I had 0 tds almost instantly. Once you add your salt, etc you're going to have TDS anyway but it's great knowing that your source water is as good as it can be for your tank.

[nekomi]

I think it's taking a little longer to break in than I expected. I did end up throwing out that first batch of water, and the next 5 gal I made up read 4 ppm. Better, but still not where I'd like it to be...

 

I'll test again this morning with the newest batch. I'm hoping that it will be all broken in now...

[Pili]

It sounds like your system is taking a pretty long time to make the water, do you have a pressure gauge in line to read the pressure going into the unit? It sounds like its on the lower side.

 

If you dont have a gauge, a good way to tell is having a ratio of about 1 gallon of pure water to 4 gallons of waste water.

[nekomi]

Thanks for the tip... yeah, it's pretty slow. It makes about 3 - 4 gal an hour. I've made abour 20 gal so far... I didn't run the system overnight because I don't have a bucket big enough to hold all that RO! Kinda sucks... I'd much rather just let it run on its own and wake up to a nice big batch of RO.

 

I don't have a pressure guage, unfortunately. It's now down to 3 ppm in the output water. Slowly but surely, I suppose... what's new, we ARE talking about reefing after all!

[BuckeyeFieldSupply]

Thanks for the tip... yeah, it's pretty slow. It makes about 3 - 4 gal an hour. I've made abour 20 gal so far... I didn't run the system overnight because I don't have a bucket big enough to hold all that RO! Kinda sucks... I'd much rather just let it run on its own and wake up to a nice big batch of RO.

 

I don't have a pressure guage, unfortunately. It's now down to 3 ppm in the output water. Slowly but surely, I suppose... what's new, we ARE talking about reefing after all!

 

Did you buy a system with a in-line GAC after the horizontal DI? If so, you'd be well served to disconnect and remove the horizontal GAC filter - its counter-productive if placed after the SI.

 

Russ @ BFS

[nekomi]

Did you buy a system with a in-line GAC after the horizontal DI? If so, you'd be well served to disconnect and remove the horizontal GAC filter - its counter-productive if placed after the SI.

 

Thanks for chiming in, Russ! Nope, the DI filter is the last stage in the filtration. After a few more gallons, the TDS went down to 1 and then 0. All is well now. It just took awhile breaking in.

 

Thank you again for the input!

[Dr.Fumanchu]

Definitely disconnect the crabon after the DI filter, its there only for taste. It will give your TDS readings. I disconnected mine after getting readings of 2-4 TDS and now its 000.

[Izzue]

Definitely disconnect the crabon after the DI filter, its there only for taste. It will give your TDS readings. I disconnected mine after getting readings of 2-4 TDS and now its 000.

 

Ya but my fish complain about the taste of the water...lol

 

Izzue

[Dr.Fumanchu]

If they dont like the taste you could tell them to stop defacating, urinating, and copulating in it.

[Izzue]

If they dont like the taste you could tell them to stop defacating, urinating, and copulating in it.

 

DOH!!!!! to much info...luckily my fish dont complain about swimming in there own crap...only how the water taste J/J

 

Izzue

[Dr.Fumanchu]

Well then go ahead and taste it and see if you agree..............

[BuckeyeFieldSupply]

Here's some text from our November newsletter that might be of interest re flushing new cartridges:

 

You heard it many times as a child, and may have repeated it to your own children: “Did you remember to flush?” When the question is posed to hobbyists following the installation of new filters, too often the response is “No.” In this article I discuss the purpose of flushing common types of new pre-filters, RO membranes, and DI resin, and describe some procedures to simplify and expedite the procedure. In general, the process of flushing new filters removes unwanted substances added purposefully to the filters, as is the case in preservatives added to some RO membranes; or unwanted remnants of the manufacturing or shipping process. If not removed from the water purification system, these substances can degrade the function of other filter stages and adversely affect the quality of the water produced. The need for flushing at the time of installation can apply to sediment filters, granular activated carbon (GAC) filters, carbon blocks, membranes, and DI resin, as well as a wide variety of specialty filter cartridges not addressed in detail here.

 

Sediment Filters

 

Melt-blown (standard or depth cartridges) or string-wound polypropylene filters, more commonly called “poly filters” are the most common sediment filters used in the aquarium hobby. Polypropylene is an ideal material for this purpose, and is the material of choice for a number of other components in the water purification trade. Other materials commonly present in sediment filters include polyester, cellulose, and urethane. Depending upon the configuration of the cartridge, surfactants, binders, or adhesives may be used during the manufacturing process. Although flushing is usually not required for polypropylene filters, follow the label instructions in this regard.

 

GAC Filters

 

Granular activated carbon, otherwise known as GAC, is a product widely used in the aquarium hobby. This media is commonly manufactured from coal or coconut shell, and has the appearance of small sand-like or larger grains. Very fined-grained carbon dust often accompanies GAC as a byproduct of the manufacturing process, and results to a lesser extent from the handling and shipping of GAC. It is this dust that can be removed by flushing. An approximate 10 minute flush is usually sufficient.

 

Carbon Blocks

 

Carbon blocks are composed of activated carbon which is ground to a powder and extruded into a tube. The process of forming a very fined-grained powder into a tube requires the addition of a binder to hold the particles together. End caps are adhered to the carbon tube. Carbon blocks don’t release appreciable amounts of carbon dust relative to GAC; however they should be flushed at first use to remove dust and remnants of binders used in manufacturing. Flush carbon blocks for 10 minutes.

 

Reverse Osmosis Membranes

 

Perhaps the most widely used membranes in the aquarium trade are the TW-1812 products made by Filmtec, a subsidiary of the DOW Chemical Company. These membranes are typically sold dry, sealed in a plastic bag. Some membranes are sold “wet” – these membranes have been tested by the manufacturer, preserved in a liquid solution, and sealed in plastic. Filmtec recommends that both the dry and wet membranes be flushed to remove the preservative solution, as well as any other substances remaining on the membranes from the manufacturing process. Flush two gallons of water through new membranes.

 

Deionization Resin

 

The final stage in many point-of-use systems used in the marine aquarium hobby of course, contains deionization (DI) resin. When installing a new DI resin cartridge, the resin should be flushed to remove any residual substances from the manufacturing process, including the dye used in color-indicating (changing) resin, as well as broken beads/fines. The flushing should consist of two to three bed volumes of water – that is, two to three times the volume of the resin. The volume of a standard 10 in. x 2.5 in. resin cartridge is approximately 0.2 gallons, so a 0.6 to 1.0 gallon flush is sufficient.

 

How best to flush new filters? Follow a few simple guidelines and you’ll have the filter in place in no time.

 

No. 1: Identify the amount of water needed to flush the filter (see recommendations above).

 

No. 2: Avoid passing flush water into other filter stages. It is inadvisable for example, to install a new GAC cartridge in Stage 2 of a multi-stage system and have the carbon fines flushed out of the GAC only to be trapped by a carbon block in the next stage.

 

Two approaches are commonly employed here, depending upon the configuration of your water purification system. In systems with a flush valve (flow restrictor bypass valve), the filter to be flushed can be placed in the housing immediately prior to the RO membrane housing, and can be flushed with the flush valve completely open. You can temporarily remove the RO membrane from your system to facilitate the flushing process. A better approach, which also avoids exposing the RO membrane to flush water, is to place the filter to be flushed in the final (post-RO membrane stage normally occupied by a DI resin cartridge. In this case, flush water immediately exits the system after passing through the new filter.

 

No. 3: Regardless of which approach to flushing you implement, never expose a Thin Film Composite RO membrane to chlorinated water. Remember that an activated carbon prefilter stage is required to remove chlorine from tap water. Nearly all RO and RO/DI systems in use in the marine aquarium hobby today utilize TFC membranes. A sure indication your system utilizes a TFC membrane is the presence of a GAC or carbon block prefilter.