RO carbon stage question

[vikubz]

The carbon stage of my unit is rated for several thousand gallons worth of use. I don't make anywhere near that in a year. Is there any reason to swap out this filter? I've had it for about a year and have noticed no problems with membrane efficiency yet.

thanks!

[Buckeye Hydro]

Yes. Remember that after the water goes through the carbon it is dechlorinated - so you should be sanitizing the system every other water change, or about once per year.

[AZDesertRat]

Another thing to remember is ALL water that enters the RO unit goes through the prefilter and carbon. This includes the waste stream as well as the final treated water so if you have made 200 gallons of RO water you have actually passed 1000 gallons or more through the carbon and prefilter at a 4:1 waste ratio which is normal.
Yet another item is some vendors supply a fairly coarse micron rated prefilter in the 5-10 micron range or even higher on no name filters with no rating. This is noteworthy because all sediment, particulates and colloidal material equal to or smaller than, and in the case of nominal rated prefilters even a very large percentage of materials larger than the micron rating get passed to the carbon block. Once the microscopic pores of the carbon block get plugged or fouled it cannot do its job and passes chlorine and volatiles on to the membrane ruining it.

Always use a very fine micron rated prefilter to protect the carbon block so it can do its job.

[vikubz]

I use a 1 micron prefilter and a .6 micron carbon filter.

I switch out the sediment filter every 4 months. How often should the carbon stage be switched, annually or more often?

[AZDesertRat]

Every 6 months unless you have a low range chlorine test kit and use it on a regular basis. It also helps to have two pressuer gauges, on on the incoming tap water line and one after the carbon block to determine pressure drop.
The problem with having a larger micron size prefiter than the carbon block is the block acts as secondary sediment filter and has to work double duty.
I use a 0.2 micron absolute rated pleated prefilter with 10x the surface area of a normal spun poly filter so I make sure almost nothing reaches my 0.5 micron carbon block.