Question re: my new RO/DI filter

[newreefer_59]

Just setup a new Captive Purity RO/DI last weekend and intially the TDS meter measured ~172 ppm on the water IN, and 0 ppm on water OUT.

I shut the water off after my reserve tank was filled, and ran the RO again last night to top-off my tank. Had it on for about an hour and the reading OUT was around 7 as opposed to 0. Any thoughts on that?

[Treebeard]

You must have a small amount of contamination in your top-off tank, probably not enough stressing over.

[hillegom]

You should empty your RO tank about 3X before using the water for the first time, and the tank should be before your DI filter