RO Cartrige

Hi everyone. I have a question. For over 2 years Im using my 90 gal. per day Spectrapure RODI filter for my 125 mixed reef. I change Sediment, Carbon and DI Resin around every 6 months, when my TDS meter shows 0.01… I have never changed RO Resin yet. I read somewhere that 2 years is mark for changing. What you guys do? Thank you for future help

 

AZ DesertRat, our water expert, answered this question in a post of mine a couple weeks ago he has had his spectrepure RO membrane for 6 years.

 

Wow. Thanks

 

The best measure of when you need to change your filters is output TDS. The membrane alone should be able to knock TDS down to 10% of incoming water with the DI resin removing the rest. Sediment and carbon block are for conditioning the water before it hits the more sensitive filters. I switch out both pre-filters every 3,000 gallons filtered. As TDS creeps up near 10%, I switch out the DI resin, and if that doesn't drop it back to 0 TDS, the membrane most likely needs to be swapped out.

 

You need 3 TDS readings to troubleshoot the system and know the membrane condition. Tap water, RO only before the DI and final RO/DI.

 

I always wonder if I am changing too soon or not quite enough.

Thank you!

 

The best indication on when to change sediment and carbon block filters is not TDS, they have very little to absolutely nothing to do with TDS. Their purpose is to remove sediment, silt , particulates and chlorine. The first three are big floaty stuff in the 1 micron or larger range, often visible with the human eye. TDS or suspended solids are in the 0.001 micron range, thousands of times smaller than either can remove.

You change the sediment and carbon filters at 6 month intervals or if you spend a few $$ on pressure gauges and a low range chlorine test kit you may be able to stretch it longer by monitoring pressure drop or headloss and chlorine breakthru.

TDS only tells you the condition of the RO membrane and the DI so is still a necessary measurement but not for sediment and carbon condition. The RO only should be able to remove down to 1-2% of the tap water TDS, not 10% which is horrible and the DI can take that last 1-2% and turn it into 0 TDS water.

 

Thank you for help. Im trying to put it in simple language so I can understand all this and try to figure this out. Seams complicated to me…Im just simple contractor…

 

Water seems pretty dirty here. I'm changing sediment Probably 2-3 months when visibly dirty. Resin I get the color changing type. The others I probably do about 3 months as well just because I'm really guessing.
I make a lot of water so hard to tell what that is in gallons.

 

Color changing resins are very unreliable. They also add TDS since it is a dye released into the treated water that is the color change. By the time the resin changes it is probably too late and weakly ionized substances like phosphates, silicates and nitrates are passing to the treated water.

Rather than changing the sediment based on color why not use a pressure gauge or better yet two gauges before and after the filters to monitor headloss. The filters can hold a lot of visible debris on the surface before they start to plug and cause headloss, might save you some money that way.