RO drinking water

what TDS level should I replace the filters at? it is reading 42ppm this morning. Not sure when to replace them. I have always just done the 6 months thing.

 

Dang dude, do it "yesterday"!!!! All the "purists" will tell you 0. The 6 months should be your first filters before your RO membrane. Of course, it depends on the quality of filter & amount of water you've made.

 

Prefilters and carbons get changed at 6 month intervals and have very little to absolutely nothing to do with final TDS. They are there to protect the RO membrane which is the workhorse and does 90-98% of the removal. RO membranes get changed when they can no longer deliver 95-98% rejection rate, usually 18 months to 3 years is the typical lifespan of a membrane.
DI resin gets changed when you first begin to see anything other than 0 TDS. This is very important as resins begin releasing weakly ionized contaminants back into the treated water even BEFORE they are exhausted. These include things like phosphates, silicates and nitrates.

At this point you need to disconnect your DI or remove the cartridge, you are probably doing more harm than good with spent resin.

Using your TDS meter, take the tap water TDS, RO only TDS and final or RO/DI TDS.

If the membrane is not removing in the 95-98% range its costing you much more for replacement DI resin than if you replaced the membrane with a better one.

Also make sure to disinfect the system while you have it apart to reduce the possibility of bacteria and virus growth in the housings.

 

I may get bashed for this, but I use just RO (no DI) for my reef for about 3 years and have never had a problem. The TDS is always roughly 50ppm. It's not going to effect anything if the TDS is around 50. It is, however, nitrate and phosphate free water..

 

this water is just for drinking though, not for the fish. They have a separate RODI system

 

50 or even 42 is WAY too high even for RO only! If your membrane is functioning as designed that means your tap water is way up there over 1000 or more. Do you have any idea what it is?
My tap water TDS is 830, we have high CO2 levels in Phx and I only have 5 TDS leaving my RO only before DI. I could not imagine a system working so poorly it produced 42 or 50. Again prefilters and carbons have almost zero effect on final TDS so its the membrane that is bad if its RO only.
Take your tap water TDS, subtract the RO TDS then divide that number by the original tap water TDS and multiply by 100 for your rejection rate.

In my case thats 830-5= 825, divided by 830= 0.9939, multipled by 100 = 99.39% rejection rate.

Do you have a final taste and odor GAC carbon filter? If so remove it and test the TDS without it since they add TDS back into the treated water.

 

I don't have a RO system. I go to one of those water stores. Water in Vegas has about 750-850 TDS.

I'm actually ordering an RO/DI later today, because even though I have never had problems using water with roughly 50 TDS, I have started stocking nicer corals and want the best for them..

 

Check Spectrapure, great special right now. AZ will tell you all about it.

 

You can't beat the deals found here when it comes to RO/DI for the western states.
http://www.spectrapure.com/email/customer-appreciation.html#1

The MaxCap systems are all I have used for several years now and I wouldn't even think of going back to a normal RO/DI now.

 

Those look nice, but I just ordered from BRS. Ryans helpful and his service is awesome.. Thanks though..