Valve corrosion condition
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The image shows two valves for steam condensate: a larger valve for the inlet and a smaller valve for the outlet. One of the valves is red inside, while the other is dark brown. Why do they have different colors?
Dark brown indicates that the water is acidic, with a low pH value, or that too much trisodium phosphate has been added; red signifies normal conditions
These are the inlet and outlet of the same pump!
The acidity of the water in the inlet area remains below 7 over the long term; the brown color is likely due to a solid solution of iron oxide and ferrous iron. Air enters at the sealed part at the outlet, and as a result the color gradually changes to iron red. I’m just guessing whether this is the reason.