what may be wrong?

[save$]

I have a oil fired hot water heater. Not a part of my furnace. It is vented into a 6 in insulated metal chimney. there is a small hole in the first foot of stove pipe off the heater. Was put in at time of installation several years ago. I am getting piles of light black flaky ash out that hole that piles up on the top of the heater. I have taken the pipes apart and cleaned it, it still comes back. I first noticed this ash after having its annual service. I've been outside and seen this ash puff out the chimney and float around. Is this dangerous? This heater uses very little oil. I have a carbon monoxide detector in the area that has not gone off and tests ok.
thanks

 

[heaterman]

If an oil burner is making soot something is amiss. Could be a lot of things but you better get someone there to tune it up. If you last service was done recently call that guy back and tell him the problem. The hole in the stack is for a combustion analyzer and the service tech should be using one. If he doesn't, he's just guessing.

 

[huffdawg]

Some possible problems are - injector tip ,flame sensor eye dirty, not enough air or ecm (electronic control module). Have you had the flue cleaned recently.

 

[save$]

Some possible problems are - injector tip ,flame sensor eye dirty, not enough air or ecm (electronic control module). Have you had the flue cleaned recently.

I cleaned the pipe going to the flue, but not the flue. I have a brush and some extensions so I can do it from inside. Never though about the flue being an issue now that I am not burning wood. The furnace people never mention cleaning the flue. I have noticed that my new roof is stained from soot around the smoke stack. I can take the pipe off the flue and look right up so that ought to let me know if it is dirty. I don't want to have a safety issue, or contribute to malfunction due to neglect.
thanks for the suggestion.