Ro/di

[bknapp]

How longs does everyone's RO/DI filters and resins last? What's your incoming TDS? How many gallons per week do you use?

Seems (to me anyways) that my filters, especially the DI resin goes fairly quick, I seem to replace all my filters and resin every two to three months.

 

[.AcroKiller.]

My sediment filter turn orange quick

 

[SmyrnaReefer]

i replace my resin every 200 gallons or less as soon as the resin changes from blue to brown...

 

[schooleyosis]

I bought the 99% rejection rate membrane from Spectrapure and my incoming TDS is around 140 and usually less than 3 coming out of just the membrane.
I replace the carbon and sediment filters every 6 months. I replace the first stage of DI resin when I start to see 1 TDS out of it on a regular basis. Last time I replaced it was in February. I have yet to replace the last stage of DI but I think they recommend every 4'th first stage first replaced to replace the second.
I only make large batches of water at a time. 20+ gallons once per week. Before I let the water out of the membrane go to the DI I run it for 15 minutes to flush the membrane out. When I first turn the water on it has about 15TDS and will trickle down to 3 or lower after the 15 minute flush. I think that really helps the life of the DI.

 

[Dowtish]

My incoming TDS usually ranges about 170. I make about 30 gallons a week, and dont change my carbon, and micron for 6 months. My have 2 separate DI chambers so they seem to last much longer. I change them every 8 weeks or so.

 

[Aqua fire/medic]

Isn't that called TDS creep or something similar?

 

[schooleyosis]

Isn't that called TDS creep or something similar?

Correct. I've read it's good to do long, less frequent runs as to short and frequent runs.

 

[bknapp]

Should I consider adding a second DI stage? What are the advantages?

Thanks for all the replies fellas.

 

[dwilliams87]

One thing to consider about the DI of you don't already know is that, once the DI is exhausted, it will begin to release what it had absorbed to begin with. Also, I've read where some people will valve off their waste side because they say "its producing to much waste". They are designed that way. If you valve off the waste, it forces what would have been waste water into the filtered water and also scales up the RO. Just a few pointers I've learned from my profession that relates to the hobby.

 

[bknapp]

Good info, thanks D.

 

[mcarroll]

I think ideally you change your prefilters based on pressure loss as well as volume of water filtered. Sediment filters clog and carbon is only good for processing X number of gallons per cartridge...or less if you have bad water. I think a lot of people aren't equipped to monitor their prefilters except for visually, so a lot of people replace the prefilters all at once when they can see any discoloration on the sediment filter. Since prefilters are generally cheap, it's not a bad cheat/strategy. (Someday I will add a pressure gauge, but for now I do this.)

Membranes can be monitored by TDS. Once they drop below their rating (often a few years if the prefilters are kept nice) they should be replaced. Be very aware that chlorine will literally chew holes in the rubber of an RO membrane, so it is crucial for your carbon not to wear out.

DI can also be monitored by TDS but many folks use color-changing (dyed) media instead. It's interesting to watch a color-changing cartridge with a TDS monitor to see how inaccurate the dye can be at indicating whether the media is exhausted or not. If you aren't equipped to measure TDS it's better than nothing, but TDS meters are cheap.

Just a few additional thoughts - hope they help!

-Matt