Deposits on water heater

[Cdibuff]

I have a 75 gallon tank water heater installed in a rental which has been running fine for the past 5 years with annual flushes. Just today I observed some sediments on it. Please see attached photo.
Can someone advise on what could cause this? Where should I begin to look?

 

[Reach4]

The well is producing more sediment?
The tenants removed the cartridge on the sediment filter on the incoming water?

What color is the sediment, and how granular is it? Like powder, or sand?

 

[Sponsor]

 

[John Gayewski]

I'm not seeing what the picture is trying to show.

 

[Fitter30]

Look at the flue pipe cap. Top of heater looks like a little bit of water might have run down the flue by the way the staining is.Water running down the outside of the flue would see a discoloration in streaks.

 

[Reach4]

Look at the flue pipe cap. Top of heater looks like a little bit of water might have run down the flue by the way the staining is.Water running down the outside of the flue would see a discoloration in streaks.

I think that would be a no-worry.

 

[Cdibuff]

I think that would be a no-worry.

This is not well water. it is city supplied lines. The water heater is only about 6 years in use. 75 gallons AO smith. The tenant also complains they smell rotten eggs around the water heater (note that the hot water isn't smelling). The staining on the top surface and the smell of rotten eggs around may be unrelated. I am thinking backdrafting? Any other thoughts on where the issue could be?

 

[Reach4]

Trap run dry? (laundry standpipe, sink, floor drain) Dead mouse?

If you put up curtains of cheap plastic drop cloths, you can separate areas. See which side of the plastic the smell is strongest.

I suspect you don't have a basement, so putting up temporary curtains would take some ingenuity.