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To RO or not to RO...before the DI

phishphood

phishphood

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So the house I'm moving into ends up with an average of 35 TDS coming from any of the 3 faucets in the place (forgot to test the hoses). So now I'm debating whether to use the RO filters before I send it through the resins. I end up needing about 6g a month currently for top off, and change maybe 12g a month saltwater if I'm good about it :) So it'll be around 20g a month usage, unless the other residents decide they want to drink RO only for some reason. So ideas whether I should use the RO, use only carbon prefilters, or just plain go straight to DI?
 
I just went through this at work. For once I used actual water chemistry experts and found the real nitty gritty. DI alone can not remove a large portion of silicates from the water. We were commercial sized DI containers and we still were getting large volumes of silicates in our water leading to diatom blooms. We stuck a RODI in front of taht unit and now we're testing zero silicates. DI will remove a lot and if your not worried about silica or your source water doen't have much to start with, DI is a perfect choice. If your on well water or have elevated levels RODI!
 
Thanks Gresham. Guess there's no way around buying another test kit then, eh? Any recommendations on brands for that? And it makes sense that DI resins can't take out something that's normally ~neutral and not ionized.
 
Silica test kits are super accurate IIRC so I wouldn't go that route. I could test it at work for you since we have the capability to test for different silicas.

Check your muni water source data, they'll tell you how much is being spit out at various times from them. It's a good "general" guide since it's only a few snapshots of a longer period of time. At your TDS I don't think you're in need of the RODI route, but only checking your source will determine that. Thales uses DI only and has no problems he's reported. I nearly went that route until I found my source has higher levels of silica :(
 
I'll probably skip the testing. City offices are closed today, and the most recent online report I could find was 2007 :/ But silica averaged 12 and 6.1 ppm and total alk tested 68 and 59 ppm. I'll probably just go DI and see how the tank reacts. It's gotta be at least as good as the water store water I hope :)
 
That's bogus, look harder online, they have to make it available.

My offer still stands if you want me to test your water. Hook up the DI and PM me your address and I'll send you a box, a bottle and a return shipping label and I'll get it tested for you.

What is you muni name, I'm good at finding these :)

It's probably better then the water store!
 
City of Sunnyvale. They get ~42% of their water from SFPUC, and another 45% from SCVWD (santa clara valley wd). I'll be in the area that gets fluoridated water from SFPUC, so I guess I'll go look for water reports from them.

City website for Sunnyvale leads to here for reports: http://sunnyvale.ca.gov/Departments/Public+Works/Water+Supply/Water+Quality+Report.htm
 
Eh, SFPUC 08 report puts silica at 5.4. I'm guessing I'll just go straight DI. Thanks for the help Gresham, for some reason I never thought of looking up water quality reports.
 
I searched and alls I can say is, drop them an email :)

pubwrks@ci.sunnyvale.ca.us
 
Sweet. I go straight DI in alameda. Nice and easy and lasts a long time unless, like me, you find you had a leak in the tubing! :D
 
Hmm, so I hooked it up and I think I have a problem. TDS from any faucet in the house: 30 +- a few, TDS after carbon prefilter etc, DI resins: 55!? :O So I guess I need to change out the resin? Would the resin every really get too saturated that it would diffuse back into the water?

Or....is the water running way too fast through the unit, or......since it's been over 8 months since I've used the unit, it might just need a massive flushing?
 
When was the last time you changed your various cartridges?

A flush couldn't hurt at all. An easy check would be to turn on your system and measure the TDS every 10 minutes. You can make a plot of this if you wish to see how long it will take to flush out, and the final level (assuming that the inactivity is the problem)
 
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