WHEN to change RO/DI filters and resin???

[JT101]

Hello All,

First off, Happy Holidays to everyone :hallo: !!

I have a Water General RD-102 6-stage system and an HM Digital in-line TDS Meter. it's a great system. I installed it last winter.

I noticed in the past few months, when I turn the system on to produce RO/DI water, the output water would read 3-4ppm (whereas it used to read 0ppm right away). I would work around this by just letting the water run for about a minute, then it would drop down to 0ppm and stay that way for as long as I needed to run the system. However, the past 3 weeks or so, the system would START at 3-4ppm, then go all the way up to 11-15ppm, but if I left it on for, say 10 minutes or so, it would, as before, drop down to 0ppm.

I assume that the system needs maintainance because of these high initial TDS readings. However, how would I know if the nitrates are low as well? Is it safe to assume that if my TDS meter reads 0ppm (meaning zero minerals and zero silicates) that I am ALSO getting zero nitrates? Or is that another animal altogether? Would I need to test the water to ensure that I am getting zero nitrates? Or, is is safe to assume that as long as the TDS meter reads 0ppm then I am OK and I can just wait until I no longer can get a 0ppm reading before I change the two sediment filters, carbon filter, two chambers of resin and maybe even the membrane?

Thanks for any advice.

John

 

[lcstorc]

Once you start to get higher reading on the TDS meter you are introducing solids of various sorts that you do not want to. Some of them turn into nitrates and some cause other problems. Do you have the color changing DI resin? If not then I would get it for next time. Often you don't need to change everything at the same time. On my unit, I have to replace the sediment filters far more often than anything else.

 

[JT101]

Once you start to get higher reading on the TDS meter you are introducing solids of various sorts that you do not want to. Some of them turn into nitrates and some cause other problems. Do you have the color changing DI resin? If not then I would get it for next time. Often you don't need to change everything at the same time. On my unit, I have to replace the sediment filters far more often than anything else.

Hi Lynne,

The problem is that even though the TDS readings go up initially, they always drop down to 0ppm if I just let the RO/DI system run a little while. The time between the initial turn-on of the system and the time the TDS drops to zero is, however, getting longer and longer (from a few seconds a few months ago to as high as 10 minutes recently). So, I always wind up using 0ppm water anyway. My main concern is what about nitrates? What part of a RO/DI system removes them?

As far as the type of resin I have, it is (according to filterdirect.com) supposed to change from brown to green when exhausted, and it is still brown, so I guess it's OK, but I'm still curious about why the system takes longer and longer to get down to 0ppm.

Thanks
John