RODI filter maintenance / water quality (noob experience)

[krash7172]

My main 2020 reefing goal is to gain more knowledge and control of water parameters. I got my first TDS meter today and I was unhappy but frankly not surprised with the results. I'm posting because I doubt I'm alone.

1) I've never checked TDS before on my RODI unit
2) I've used visual cues like sediment filter and DI color mostly to determine when to change
3) I had a mental schedule of how often the different filters and membrane should be changed. And I didn't really follow it.

So the results of my testing are 370 ppm in and 75 ppm out. It's obviously time to change. I'm curious how these levels might affect the tank. For example, I have 40 gal mixed for WC. Is it important enough to dump and wait for new filters or generally OK to use? I've obviously been doing WCs with high TDS and the tank looks good.

 

[Scrubber_steve]

if the pressure drops on your gauge - change the sediment filter.
if the total chlorine reading on your test strip gives a reading above zero - change carbon
if your TDS gives a reading above zero - first test the output after the osmosis filter & before the DI resin. If reading is more than 5% of source water reading - new osmosis filter
If after that the TDS reading after the osmosis & DI resin is above zero - new DI resin.

 

[Cory]

I agree with scrubber steve. I think its most important to change out carbon frequently because its mostly chlorine that destroys your ro membrane. I have two sediment filters, and three cheap carbon filters. I change out a carbon every month. Sediment is changed when its very black or brown and presure drops. I dont use deion resin because my membrane produces 1 tds or 0 from 135 tap water. Spectrapure select plus membrane is working great for me.

 

[DesertReefT4r]

if the pressure drops on your gauge - change the sediment filter.
if the total chlorine reading on your test strip gives a reading above zero - change carbon
if your TDS gives a reading above zero - first test the output after the osmosis filter & before the DI resin. If reading is more than 5% of source water reading - new osmosis filter
If after that the TDS reading after the osmosis & DI resin is above zero - new DI resin.

All good info. Also bleed off the RO water before the DI for the first 5 minutes of operation. The TDS will be high for the first few minutes known as TDS creep, it will cut down on DI usage. Flushing the membrane is helpful in increase its life and water production. This can be done with a flush valve kit or simply bypassing the restrictor valve on the waste line. Last tip is run the RODI as long as possible, short on and offs to make small amounts of water will reduce membrane life. I make all the water I may need at once normally 20 gallons.
Edit:
I agree on Spectrapure membranes, very high quality and great rejection and production rates. By accident I bought the normal 90gpd membrane not the select plus membrane and its still putting out 3 tds after membrane almost 2 years later, getting 98% rejection since new. I get all my other filters and di from BRS.

 

[krash7172]

Yeah. My carbon is old and I'm replacing everything. Just wondering how harmful my previous practices were and if my batch of water should be dumped.

 

[Cory]

Yeah. My carbon is old and I'm replacing everything. Just wondering how harmful my previous practices were and if my batch of water should be dumped.

75ppm tds could be 75ppm of anything. I wouldnt use it but if everything is fine with this water before id use it once and get a new filter set.

 

[Scrubber_steve]

Yeah. My carbon is old and I'm replacing everything. Just wondering how harmful my previous practices were and if my batch of water should be dumped.

75 ppm out ,,,, that's higher than my tap water reading

 

[krash7172]

So you don't need RODI. Nice!

 

[Scrubber_steve]

So you don't need RODI. Nice!

yes, still need RODI. Need zero TDS.

 

[krash7172]

I know. Poor sense of humor

 

[Cory]

I agree. You may be fine with ro only like mine at 0 to 1 tds but not higher.

 

[Scrubber_steve]

I know. Poor sense of humor

Sorry, should have known you were joking.

 

[krash7172]

Ok, back to serious. My LFS offers tank maintenance service and I inquired because this is my first reef tank. I ended up deciding to go it alone (with the help of R2R). They said watch the color of the DI and sediment stage. Change membranes once a year. I thought I was doing a good job. Not really...

 

[krash7172]

I hate being wasteful but I dumped and cleaned my mix tank. Replaced all filters and membrane. ZERO TDS! I know it's probably simple to the experts but builds confidence for us noobs when we get another variable under control.