RO/DI TDS WDYT??

[Enigma13]

I do not know why someone else has not clued in to this already, but the water should flow through the carbon block before the RO membrane. Your description above says that the carbon block comes after the membrane. The carbon block is the key to removing chlorine which will toast the RO membrane and the carbon block will also remove some bigger ions like calcium etc. that can clog the membrane. By having it routed so the carbon is after the membrane you really have bypassed the safety mechanisms for the membrane and it is probably toast. Membranes run about $80-100 as mentioned above. Your flow patterns should be as follows sediment, carbon 1, carbon 2, membrane, DI1, DI2.

[hobogato]

Your description above says that the carbon block comes after the membrane. The carbon block is the key to removing chlorine which will toast the RO membrane and the carbon block will also remove some bigger ions like calcium etc. that can clog the membrane. By having it routed so the carbon is after the membrane you really have bypassed the safety mechanisms for the membrane and it is probably toast.

i did not mention this because mike said he had two carbon cartidges before the membrane and the carbon block after. if it were me, i would do what you said and put the carbon block before the membrane as well.

Membranes run about $80-100 as mentioned above.

buckeye field supply has filmtec membranes - 100gpd for around $45.

[Instar]

The description is actually a bit deceiving. I believe the "sediment" filters he refers to are actually 1 (as in single tower used for this) fibre sediment pre-filter at 5 micron mesh size and then the next 2 towers are 2 medium grade carbon blocks of 5 micron particle porosity, then into the RO membrane. The last 2 are the DI and then that little carbon tube thing (referred to as a carbon block) is presumably to capture any last junk if the DI resin is expired or leaches because it wasn't changed soon enough. A useless piece so long as everything is working and maintained correctly.

One question not answered yet: You do not need a second DI cartridge once you are setup and operating correctly.

[caferacermike]

More money more problems.

I'm retiring it to make lime flavored Kool-Aide. I don't have another couple of hundred dollars to "play" with again.

Instar thanks for helping. It's not your answers it's the lack of funds. Oh and when I said $400 I was not referring to a new membrane. I was relaying my feelings about ever getting setup with a new RO unit. As in $400 would buy me years and years worth of 5g fill ups at the lfs at 10 cents a gallon. Since I'm at the shops about twice a week anyways it doesn't matter to me to haul those jugs around. And now that I actually set one up instead of succeding I only wasted my money.

[safeuerwehr]

according to Brian at purity 100gpd membranes have about a 90% rejection rate as compared to a 75 or 50gpd which have a 98-99% rejection rate...so in essence your output out of the membrane will be high and thus eating up your DI resin in no time.....

[BuckeyeHydro]

We do a steady flow of business re working these systems once folks understand just what the bought. This is a little confusing because of some conflicting jargon used above, but best as I can understand:

You have three vertical housings, which contain, in order of water flow: 5 mic sediment filter, `1 micron carbon block, 5 micron carbon block. Then a 100 gpd knock off brand 1oo gpd membrane, then a horizontal DI housing, then a in-line taste and odor (GAC) cartridge.

Your tap water has a tds of 154, your RO lowers that to 38, and your DI lowers that to 22. For sake of discussion let's assume these readings are accurate.

Let's talk about the configuration of the system, and then how your particular system is working.

In general, you want to protect the carbon blocks with your sediment filters. So the final sediment filter (you only have 1) should have a pore size smaller than or about equal to the pore size in the subsequent carbon block. You have a 5 mic sediment filter followed by a 1 micron carbon block. To maximize the performance of your system you'll want to go with a 1 micron sediment filter ahead of a 1 micron carbon block(s), OR go with a 5 micron sediment followed by a 5 micron block(s). Bottom line - use your carbon blocks to adsorb VOC's, not act primarily as sediment filters.

Next, you have a 100 gpd membrane. Unless you can determine the brand name, no telling what to expect from it.

Next you have a relatively small, horizontal DI housing. Horizontal housings for DI resin are a fundamental design flaw. For a short-term fix remove the DI housing from its current position and mount it in a vertical position with the water frlowing from the bottom up. For a better solution get a full size, vertical DI housing with a refillabel cartridge.

Now, assuming your DI resin was operating as it should, you then take water that is as clean as you can make it and run it through GAC. Another fundamental design flaw. Remove the final horizontal in-line GAC cartridge. It is not needed and is counterproductive in the current configuration of your system.

Now, on to the performance of your system:
Your membrane is rejection only about 75 % of the tds in the feed water. Assuming you have adequate pressure, you can do 90%+ with a 100 gpd Filmtec membrane; and 96to 98%+ with a 75 gpd or 50 gpd Filmtec membrane. I recommend you replace the membrane.

You are getting 22 ppm tds water after it comes out of the DI and has passed through the GAC. First, as mentioned above, get rid of the post DI GAC. Run the system again for a few minutes and get a post-DI reading again. It may be near 0. Remember that the post DI GAC will ADD dissolved solids.

Russ @ BFS

[caferacermike]

Thank you Russ. That was the most complete answer I could have ever expected. You took the time to not only read but understand what I wrote. I now understand my system better than ever. You are correct about the GAC filter being last. I had no idea that it can ADD solids. I was impressed by your prices, checked em about 3 days back, IF I decide to give it another try (probably not until after the holidays) I'll bring the entire unit by and get all new cartridges from you.