Iron in City Water Supply

[Jim Tibbetts]

What forms of iron might typically be found in a city’s water supply? In particular, what form of iron could cause my whole-house water filter, time after time over 2+ years, to turn a dark “rust” brown color within 2 to 3 weeks?  Please see attached photo.

Our Pasco County, FL water, of course, meets the EPA limit of 0.3 mg/L iron, so what “other iron”, if iron is what I’m seeing, is causing this rapid? discoloration of my filter elements?  

My store-bought test strips indicate iron at less than 0.3 mg/L, but are these strips only picking up “dissolved” iron, ie iron ions.  If there are minute “flakes” of rust from iron pipes in the county’s water supply system, I’m guessing my test strips will not detect that iron, unless ions of iron migrate from the iron particles into the surrounding water.

Also, I have been told that if phosphates are used in the water treatment process, which is apparently not uncommon, that this can cause the rust colored “stuff” that my filter is capturing.

Obviously, I’m shooting in the dark here, but any explanations for what I’m seeing here will be much appreciated.

 

[StringJunky]

The Florida limit is 300micrograms, not milligrams.

https://www.floridahealth.gov/environmental-health/drinking-water/_documents/iron-fs.pdf

Is it well water? In a glass, does the colour settle as particles or remain uniform throughout the water? If it settles it is Ferric iron and the soluble form is ferrous.

Edited June 16 by StringJunky

[Jim Tibbetts]

Our water is not well water but comes from Pasco County, Florida municipal water supply, which is alleged to meet EPA requirements of 0.3 mg/L, which in Florida is same as 300 mcg/L.

Like the quote, one of my favorites:  “Man’s most valuable trait is a judicious sense of what not to believe.”    Euripides

I have hundreds more but I’ll spare you.

[StringJunky]

10 minutes ago, Jim Tibbetts said:

Our water is not well water but comes from Pasco County, Florida municipal water supply, which is alleged to meet EPA requirements of 0.3 mg/L, which in Florida is same as 300 mcg/L.

Like the quote, one of my favorites:  “Man’s most valuable trait is a judicious sense of what not to believe.”    Euripides

I have hundreds more but I’ll spare you.

I ballsed that one up!

[CharonY]

Assuming that is iron and it is insoluble, it is going to be some kind of iron oxide or hydroxide. Most methods to quantify them (which I know) are not really suitable for DIY testing. You could open up your (used) filter and/or get a sample before to the filter (if you have a bypass valve) to check whether you have got visible turbidity (use a clear glass and white background to check for discoloration). Typically, municipalities also provide water testing (for a fee). A way to deal with that (other than replacing lines) is to use a backwash filter, I believe.