Residue using cold water pot filler

[Anonymous]

We had a pot filler installed with a renovation. I've noticed when I boil pasta with just salt, rather than the normal white residue/water line after I'm done, I'm finding a brownish residue. Any ideas why this would be happening? I tested a pot full of water from the sink faucet with pasta- no residue. The sink waterlines are new. The pot filler repurposed the original water lines, I believe.

[Anonymous]

If you have a water filter on your drinking water lines but not the tap, could be iron or tannin. Are you in city water?

[Anonymous]

OP here. We are in Silver Spring.