TDS readings

[usmc121581]

This is a stupid question but want to make sure I buy the right filter. The water coming in is at a TDS reading of 110ppm, then the water coming from the RO is 10ppm, but the water coming from the DI goes anywhere between 25-70. I just want to make sure that I should buy a DI cart. and not a RO and DI cart. Need to save money and dont want to buy more then I need.

[AZDesertRat]

You definitely need a new DI cartridge for sure.
A RO only TDS of 10 with a tap water TDS of 110 is not all that great, thats only 90 or 91% rejection. Do you by chance have a 100 GPD membrane and not a 75 GPD membrane?

Prefilters and carbon block have almost no effect on final TDS but do need to be changed every 6 months to protect the RO membrane. Factory carbons are often low quality and if you go very long they can let chlorine through to the membrane and ruin it. Always use high quality replacements no e-bay quality stuff, there is a big difference.

DI resin should be changed when you begin to see anything other than a constant 0 TDS. What people don't realize is DI resin starts to release the contaminates it has cillected once it starts to near exhaustion, it doesn't even have to be shot yet. It releases weakly ionized substances first and some of those are nitrates, phosphates and silicates all of which are bad news.

If you have not replaced the prefilter and carbon in the last 6 months do so now along with the DI cartridge. Remember to disinfect the housings while you have the filters out. You should have received directions on how to disinfect it when you bough it, if not you should be able to search it here on RC as ity has been posted hundreds of times.

[usmc121581]

Thanks, The filters are not even 4 months. the RO is about 3 months along with the DI resin. The DI resin was bought off a water purification web site(never again). Now Im in search for DI resin.