RO/DI cartridge question

[Ernie C]

How often should I replace the cartridges in my ro/di unit. I just replaced them all including the ro membrane and di resin. I don’t use it to make salt water only for top off. So I would say like 10 gallons a week. TDS meter has always read 0 but had terrible algae outbreak and source ended up being my top off water. Now I’m paranoid. Any advice would be appreciated.

 

[Crabs McJones]

Ro membranes are on average good for 3 years. Pre filters I change out every 6 months, and di is changed out when its around 75% depleted.

 

[Ernie C]

Ro membranes are on average good for 3 years. Pre filters I change out every 6 months, and di is changed out when its around 75% depleted.

Thank you for your input. I have the color changing resin. So I should change that out as it starts turning orange from the bottom up at 3/4 of the way?

Also, is it correct to say that zero tds doesn’t mean no nitrates and phosphates or other stuff in the water?

 

[redfishbluefish]

I have my original membrane...maybe 11 or 12 years old. Now I do measure TDS post membrane, and that tells me it's still working just fine.

The other filters (sediment, and two carbon blocks) are changed yearly. The DI only gets changed when the post DI TDS meter reads anything but zero....which is about yearly.

 

[Crabs McJones]

Thank you for your input. I have the color changing resin. So I should change that out as it starts turning orange from the bottom up at 3/4 of the way?

Also, is it correct to say that zero tds doesn’t mean no nitrates and phosphates or other stuff in the water?

I believe a TDS will be able to measure phosphate. But there are some things that can get through undetected.

 

[lapin]

Thank you for your input. I have the color changing resin. So I should change that out as it starts turning orange from the bottom up at 3/4 of the way?

Color changing resin will change color. This is not exact science but an indicator that is might not be useful anymore. You need measure your tds output, then you will not know if it is used up.

Let me say I change my sediment filters about 1x a month. I make 70 gallons a week. I have rainwater. My in coming tds is 11. Most of the crud is not dissolved but pollen and stuff that comes off the roof and makes it through my home filtration system. Sort of like weak tea. After 1 year of making water my ro is letting 1-tds thru to the resin. Hopefully it will last a lifetime.