Black sediment in whole house filter

[Wbigelow]

We are on a 115 foot deep well put in 12 years ago, submersible pump, pressure tank, whole house sediment filter using polypropylene wound cartridge, water softener using standard salt, then cold feed to the house and feed to electric hot water tank that then feeds the house. Replaced hot water about 8 years ago, and replaced the rod a year ago. All is working fine.

We have somewhat high iron in the water that the filter and softener takes care of. Have to change out the filter every 3-4 months when we notice diminished water flow or high iron coloring in toilets. It is always iron rust red.

Now the odd part. Noticed reduced water flow and increased iron staining, swapped out the filter today and it was BLACK. Not slimy, not smelly, had black particles in the filter casing, they are not hard and do smear, most of them but not all. Filter was black/ dark grey throughout. Have not noticed anything different in the water at any faucet or I use.

Is my pressure tank diaphragm failing? Well or water problems? Other ideas???

Thanks

[pawaterguy]

Could just be manganese. A quick test will tell for sure. The filter and softener will remove it if that's what it is.

[PRR]

All "iron" in water is compounds, mostly oxides. There are several iron oxides. Some red, some black. Some will turn one to the other with air or temperature.

IIRC, we find black oxide in sealed boilers which have limited oxygen, red oxide out in the open with unlimited oxygen.

As Pa says, manganese is often found with iron and may be brown to black.

Test is good idea.

I've seen a rotted toilet-flapper spew a lot of black crud, but I think (hope) that pressure tanks are made of better stuff.

Wonder if your well-head is sealed to surface contamination. We used to have a shallow well which would get gumpy in autumn as fallen leaves mouldered above it. However this added "flavor" which you do not report.

How does the softener salt look?