[jiggly75]

Hello everyone,

I have an RODI system with an inline TDS meter. How high should I let the reading get before changing cartridges?

Thanks in advance for any advice .

[charlie]

I usually change mine when the TDS gets to 8-9. To be honest, I don't think I've ever seen this discussed, I'm curious as to what other people think too.

[Reefland]

I don't really monitor the TDS from our wter, do test occassionally but that's it. I let the color of my sediment cartridge dictate when it's time for a cartridge replacement.

I would suggest that an increase in TDS of 10-20 would indicate time for a change.

[kevinpo]

I change my RO membrane when it reads 10ppm or higher and the DI cartridge when it gets to 5ppm. If you let the TDS reading of your RO get to 20ppm or so the DI cartridge will last about half as long as it would at 10ppm because you are asking it to do twice the work.

Here's a little tip:
For people who have very high TDS from their tap (250ppm and up) you can run 2 RO membranes in series and really extend the life of your DI cartridge. I'm lucky here that the tap water runs about 79-84ppm most of the year. There are areas out of the valley here that run 350-400ppm

Regards,
Kevin

[middlemark]

Thanks for that nice synopsis, Kevin.

I personally found that `used up' DI eventually seems to give back TDS.

I had gone too long without testing this summer [around my wedding, filter changes weren't on my to-do list, nor was money easy to come by] ... and ended up testing my DI's output at around 30. As the water I got out of the RO was at 5 ppm - I came to believe [could be wrong] that the spent-DI was actually putting crud back in the water.

Ended up just using RO until when I could get a DI change. Got DI resin, refilled and went back to zero [and macro which had appeared on rocks disappeared].

[Unresistible Blue]

[quote=middlemark]Thanks for that nice synopsis, Kevin.

I personally found that `used up' DI eventually seems to give back TDS.

I had gone too long without testing this summer [around my wedding, filter changes weren't on my to-do list, nor was money easy to come by] ... and ended up testing my DI's output at around 30. As the water I got out of the RO was at 5 ppm - I came to believe [could be wrong] that the spent-DI was actually putting crud back in the water.[quote]

You are correct - leave exhausted DI resin in too long and it will add tds to the water.

Blue