Black stains on customer's wash

[wildimaginations]

Customer was complaining of black stains on all of her wash.  Determined stains are not grease or residue from using too much detergent in her LG front load washer.  Disassembled supply water lines and found black residue on hot water filter screens.  Also found out that customer's water heater had failed.  Unable to find out what the black stains were but they did get through the filter screen into the wash.  Replaced water valve and advised customer to have plumber flush the lines after water heater repairs have been completed.

[AJ]

Interesting, wonder what that black stuff is.

[theoldstoveguy]

Iron algae looks like.At least that is what it looks like. Common in Northern CA.

[PARTech]

Think I may be calling a cust and going back out, I never thought of the water supply......

[rego]

I have done some water heater service work for a few year's and haven't run into any black particles only white from deteriating dip tube.

from www.mass.gov no idea if it helps but interesting.

Black Particles
 
Black particles can come from four common sources:
 •The inside of a steel pipe,
 •A broken water filter,
 •A degrading faucet washer or gasket, or
 •A disintegrating, black rubber, flexible supply line hose (these same hoses are also made as flexible water heater connectors).
 
Particles from the inside of a steel pipe are discussed in more detail under the brown or orange particles section.
 
If the particles are very hard, similar in size and shape, and might be described as large coffee grounds, they are probably granular activated carbon (GAC) from the inside of a GAC water filter. To stop this problem, replace the filter cartridge or consult with the manufacturer of the unit or the salesperson who sold it to you. If the particles are small black specks that might be described as being oily or sooty in texture, they are probably from the inside of a flexible hose. Over time, the chlorine or chloramine in the water causes the rubber to break down. To stop this problem replace the hose with one of the new styles that have a water disinfection resistant lining (clearly advertised on the label) or change to a different style of hose that is not made of black rubber.

[rego]

Another interesting one:

Summary of Treatment Options for Iron and Manganese

Symptom                            Cause           Treatment

Water clear when drawn,            Dissolved iron or    Water softener (less than 5 mg/L of
reddish-brown or black particles   manganese.           iron)
appear as water stands; reddish-         Aeration (less than 25 mg/L of iron).
brown or black stains on fixtures         Oxidation/Filtration (less than 15
or laundry.                       mg/L of iron plus manganese).
                     Chlorination-Filtration (greater than
                     10 mg/L of iron).