Tank Cleaning
First of all to clear up the misconception of cleaning sludge from a tank without cutting the tank open, will not clean the tank well enough to reduce that terrible clogging at your burner's filter every time you have oil delivered. This will only be a very temporary solution to your problem. As for cutting the tank open and cleaning out the sludge, this is a practice that is no longer used. The only way to truly get all of the sludge out of the tank is to remove the tank all together and install a new one. Sludge is a form of bacteria that develops over time inside the tank. Once you start to experience this problem, new supply and return lines from the tank to the burner will correct the problem for a while. However this is not a permanent solution either. As for larger commercial or industrial tanks that have built in access for cleaning, its always a good idea to have the tanks cleaned on a regular basis. Most steel tanks used for fuel oil storage in a residential or commercial application will have to be removed and replaced when sludge build up starts to pose a problem. This is usually a good indication that the tank's life is near or at the end of its useful life.