Ongoing issues with phosphates

Came back from a two week vacation to find out that my phosphates read about 0.13 ppm with my Hanna checker. Two weeks and about 3 cups of GFO later, phosphates are still hovering around 0.15 ppm.

Last night decided to test my top off water, the first test came back at 0.07 ppm. I have a BRS 6 stage RODI unit with two DI cartridges. The unit is exactly one year old and has produced a lot of water since then. If Hanna is right, my DI resin is shut and needs to be replaced. In theory, constant top off with RODI fresh water at a rate of 1 gallon a day and 0.07 ppm of phosphates can raise phosphates in the display tank to the levels that I’m seeing. Even with rapid filtering with GFO…

Plan for this weekend:

  • replace DI resin in both cartridges
  • make fresh RODI top off water
  • test top off water for phosphates/nitrates
  • if everything is good, replace GFO and wait for phosphates to drop in the display.

Unless there are other problems, phosphates should drop back to < 0.05 ppm within 10 days and 2 cups of fresh GFO…


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