RODI filter change frequency

[mling]

My reef is over 10 years old but has been neglected until I recently retired. I have a BRS 5 stage RODI and I replaced all filters one year ago. 

TDS is getting embarrassingly high.  I currently only have Leathers and other corals that don't care about water quality. Fishes are fine, Maroon clown is over 15 years old.

 

I know you don't have to replace the membrane every year.  What about the other 4 filters ?  

Should you change all 4 at the same time ?   I have one 1 Micron Sediment, two 1micron Carbon Block and DI Resin

Would changing the DI Resin alone be enough ?

[Jon Lazar]

If your unit is producing more than 1-2 TDS, then your DI resin is about exhausted.  Your RO membrane should reduce your TDS by something like 95%, and the DI resin removes whatever is left.  Do you know what your TDS in and out of the actual membrane is?  You can remove the DI cannister and run the unit, and measure the output.  This will tell you whether your DI is simply exhausted (which I would expect after a year), or whether your RO membrane isn't working right.

 

Changing the DI resin will definitely lower the TDS of your output water; probably all the way to zero.  But that doesn't address the underlying problem if your RO membrane is producing high TDS.  In fact you could remove the filter, carbon, and RO membrane and run it with only DI resin.  But it will exhaust your DI at least 10x faster and that's expensive.

 

You should replace your sediment filter when it gets clogged and reduces flow.  You should replace your carbon when it starts letting chlorine past, either because its chemically exhausted or because the carbon is clogged from sediment that the filter didn't catch.  These things are hard to measure, so most people change them when the prefilter turns color or after some amount of time.  Similar to "12 months or 12,000 miles".

 

 

Edited August 7, 2020 by Jon Lazar

[DFR]

It all really depends on your use, and condition of other filters.  I normally change my carbon blocks and sediment filter when the sediment filter looks dirty/brown (the best practice is probably to test the water leaving carbon block to see when it needs to change).  Since you’re using the BRS unit, it probably has the color changing DI resin.  That should be changed when when there is about an inch of dark blue resin left at the top of the canister.

 

As to your comment on stocking, you’re right.  You’ll probably be fine using just regular tap water.  I honestly didn’t start using RODI water until I started dabbling with stony corals.  Prior to that I mostly did fish only or anemones and mushrooms, and they were all fine for years.