R/O- break in time?

[yakfishin]

I've been using the same brand r/o filter and deionization cartridge for a couple of about 5 years now. I have had to change the filters a couple of times and in the past, and I only had to run water through for about 10 minutes before I started to catch the finished product for use. I changed both my r/o and di filters this time to high silicate removing cartridges due to what appears to be some diatom growth. When first changed and ran the unit for about 10 minutes and my TDS read 20ppm. I have since filtered about 5 more gallons and now my TDS reads 6ppm. I checked the TDS readings in between this period and they have just steadly dropped a few ppm's which each gallon being filtered. I'm guessing (and hoping) that after running the unit for awhile longer I'll be down to 0ppm. Does this seem to be usuall for some filters, or is it a sign that something might be wrong?
Thanks.

[EverettReef]

I replaced my RO membrane this past weekend. It took about 20 minutes for the TDS to drop to 0. The TDS of my source water came in at 38 on Saturday. The recommendation for the new membrane was to make 2 gallons of purified water before starting to use the purified water. I just waited until the TDS dropped to 0. My first time with dual TDS meters. Makes me feel good about the quality of the water I am producing.

[yakfishin]

Thanks. I guess perhaps there is a difference between the membranes in how long they take to get to 0 TDS. The membranes I used before only took a couple of minutes before registering 0. I have run my new ones for about 5 hours now, probably about 8 gallons of product water, and I'm still not quite to 0 yet. But it is dropping a little at a time.

[Brian.Bentzen]

My RODI unit recommended 24 hours of use (25 gallons)

[WaterKeeper]

We are talking about the RO section here, aren't we? The RO should break in after about a few gallons but, as Brian said, it may take longer. However. the DI section will remove just about everything the RO misses and it only needs a breakin of about 3 times the resin canister volume before it is fully functional. The only big drawback of having high TDS in the RO's effluent is decreased life of the DI stage.

[yakfishin]

Waterkeeper- I guess I'm talking about both the RO and the DI together because my unit has both. I'm wondering if I might have my DI cartidridge in upside down. Is that possible? The cartridge is a HI-S DI by Kent, but the marinedepot website said it is interchangeable with captive purity RO/DI units. Now I'm starting to wonder if this is true.

[WaterKeeper]

I think those are mixed bed DI cartridges so they is no need to have flow in any sepecial direction. The resin will work either way but the fittings on the cartridge may have different seals on the top and bottom so it could leak if installed backwards.

[yakfishin]

You are the man when it comes to water issues!! I'll go home tonight and switch the cartridge around, there is a different seal on the top and bottom but it didn't have directions that said what is the top and what is the bottom, I figured I had a 50/50 chance of putting it in correctly if there was difference. If it matters, about 1/4 of the cartridge had a very different look to it than the other part. One part is blue and the other part had more of a greenish look. I'm sure I have given it enough time to read 0 if everything was installed correctly. Thanks again.

[WaterKeeper]

Well, there is a 50% chance I am right. :D

That small portion is probably whatever they use ( I tend to guess activated alumina) to reduce silica but most DI resin will do that anyway; so I somewhat wonder about the benefits. Back when CA, cellulose acetate, RO membranes were used in such units it may have had an advantage to use an Si removal resin as CA membrane were not very good at Si removal. Today's TFC, thin film composite, membranes do a much better job and usually get nearly 90-95% of silica.

[yakfishin]

I came home from work thinking I would try turning the DI cartridge around, only to find out that it won't fit in the canister that way. I knew the canisters were a bit wider up top then at the bottom, but didn't realize the DI cartridge was shaped in the same way. I have what I'm guessing to be a slight diatom problem, even though my aquarium is about 3 years old now. I have a couple of spots on my live rock that have a brown crusty coating. Almost reminds me of brown colored coralline. It grows very slowly, but I'm hoping to get it to stop growing. I tested my product water and it showed a very slight level of silicates, lower than what is generally considered a problem, but I thought I would try the HI-S RO membrane and HI-S DI to see if it helps. But it might not even be diatoms. I have increased my water changes and also increased my PH which I found out had been lower than I had thought. This seems to have slowly allowed my purple and pink coralline to start out competing the brown stuff. But it's been a very slow process. My product water is now testing 2 TDS. It too has been a slow process but it is continually dropping. I wonder if something is possibly wrong with the DI cartridg? Perhaps it really isn't interchangeable with a captive purity RO unit? But according to marinedepot it is.

[yakfishin]

Ok, after having run this filter for approx. 10 hrs now, my tds is still somewhere around 2-4 ppm. Tonight I'm going to scrap the HI-S filters and replace with the standard filters I had been using for the past few years. I should have never tried something different. Live and learn.

[WaterKeeper]

You know I just looked at a pic of the cartridge you are talking about and it may have a carbon stage. If you are passing RO/DI through carbon then the TDS will climb as it leaches material from the carbon. That is why carbon prefilters are always at the head end of the system.