3 stage fitler, DI, and tds-0 and still phosphates??

[Sir Patrick]

Just wondering-

A 3 stage filter, DI, and tds-0 and still getting phosphates?? Is this right??

[jimsflies]

Phosphates in the RO effluent or in your tank?

[Sir Patrick]

Phosphates in the fresh made ro water, before storage in a container of any kind.

[AZDesertRat]

There should not be phosphates if it is designed and working properly. Saltwater phosphate test kits , in fact most all hobbyist type test kits are not reliable in RO/DI water, they are designed for water with various ions in it not ultrapue water.
What are you testing with? What prefilter, carbon block, membrane and DI configuration, vertical bottom up or horizontal, and resin blend are you using.
Phosphates are weakly ionized so it takes good DI resin in a properly packed vertical canister with good contact time to be effective, another problem is since they are weakly ionized they may not register on a hobbyist grade TDS meter.