Chimney Sweeping Methods and Tools

Four questions that pick the method

Before any tool goes up a flue, a sweep is answering four questions, usually during the first look at the system:

1. What is the flue made of? Clay tile, cast-in-place mortar, a stainless steel liner, the inner wall of a factory-built chimney pipe, or bare masonry in an old unlined flue.
2. What shape and size is it? Round, square or rectangular, and how large. A brush that does not match the cross-section leaves corners or edges untouched.
3. What is in it? Light, dry soot; crusty, flaky creosote; tar-like or glazed creosote; oil soot and scale; nesting material or fallen debris.
4. Where can the work be done from? The firebox or appliance, the roof, a cleanout or a removable section of pipe.

The rest of this guide goes through the tools in that light. For the visit as a whole, including how the room is protected, see what happens during a chimney sweep.

Brushes and rods

The basic tool is still a brush on a string of rods. The rods screw or clip together, so the brush can be pushed the full height of the flue a section at a time. Rods are flexible enough to follow a gentle offset in the flue and stiff enough to push the brush through deposits.

Brushes differ in three ways:

• Shape. Round brushes for round liners and pipes, square or rectangular brushes for clay tile flues. The brush should fill the flue so its bristles bear on every wall.
• Size. Too small and it rattles through without scrubbing; too large and it jams or wears the liner.
• Bristle material. Steel wire bristles scrub hard deposits off masonry and clay. Polypropylene (poly) bristles are softer. Stainless steel wire is another option for some metal liners.

Bristle material is where manufacturers draw lines. DuraVent's instructions for its DuraTech Premium factory-built chimney tell owners to clean it with plastic or stainless steel brushes and not to use a brush that will scratch the stainless steel interior. Its instructions for the DuraLiner liner list plastic, wood, or flexible steel or wire brushes and say not to mar the liner surface. Two products from one maker, two slightly different lists, which is why the specific instructions for the chimney or liner in front of you are the ones that count.

Matching the tool to the lining

Cast-in-place and resurfaced flues follow the system maker's guidance. A flue with damage seen on camera may be swept more gently or only partly until repairs are planned. For lining types, see stainless, cast-in-place or clay liner.

Rotary tools

Rotary sweeping uses a drill or motor to spin the rods, or a flexible cable, inside the flue. At the business end there may be a brush, flexible plastic or cable whips that flail against the walls, or heavier heads for stubborn deposits. Spinning lets the head scrub all the way around the flue with every pass and reach deposits that a push-pull brush slides over.

CSIA's homeowner guidance on creosote says that when creosote is crusty, or fractures when hit, rotary cleaning can be helpful for removing it. Rotary heads have the same limits as brushes: they have to suit the liner material, and a head aggressive enough to break crusted creosote off clay tile could damage a thin metal liner. Rotary tools are also useful for clearing debris, such as an old nest packed into a smoke chamber, once the animals are gone.

Chemical treatments, and where they are not allowed

Not every deposit can be scrubbed off. CSIA explains that when creosote is gummy, about the only way to deal with it is a chemical treatment or an acid application. These treatments change the deposit so it can be brushed out later, which often means more than one visit and some time between them. The stages of creosote are explained in creosote: stages, risk and removal.

Chemical products are not universally allowed. DuraVent's DuraLiner instructions say not to use chemical chimney cleaners, warning that they do not eliminate the need for mechanical cleaning and may be highly corrosive. A sweep has to know what the flue is made of before choosing a chemical method, and in some systems the answer is that the deposit is removed mechanically or the liner is replaced.

Homeowner products are a separate category. CSIA says creosote-removing products that are burned in the fire are promoted to remove a portion of the creosote through catalytic action, and that using them alone is not an adequate substitute for mechanical cleaning and inspection. See creosote sweeping logs.

Heating flues, stoves and coal

• Oil furnace and boiler flues. CSIA describes the annual service as disconnecting the pipe that connects the oil appliance to the chimney, sweeping it and reconnecting it, removing the loosened soot and sweeping the flue if needed. Much of the material in an oil flue collects at the base, so access to a cleanout matters as much as the brush. See oil furnace and boiler flues.
• Wood stoves. The connector pipe and the area above the stove's baffle are cleaned along with the chimney. Some installations allow sweeping down from the roof into a tee or cleanout; others require taking the connector apart.
• Coal. Coal deposits contain sulfur. DuraVent's DuraTech Premium instructions say the sulfur and ash combine with moisture to form a highly corrosive acid, call for cleaning within 48 hours of shutting down at the end of the season, and describe wiping the flue with a brush wrapped in a rag dipped in a strong baking soda and water solution.
• Gas flues. Usually little soot, but debris, nests and bits of deteriorated masonry at the base. The work is more about clearing and inspecting than scrubbing.

Vacuums, covers and the tools you do not see working

Much of a sweep's equipment is there to keep soot out of the house rather than to remove it from the flue. A powerful vacuum made for fine soot runs during the work, connected to the sealed-off fireplace opening or stove, so air is drawn into the chimney side rather than out into the room. Drop cloths and a cover over the opening complete the seal.

Hand tools fill the gaps between the big ones: scrapers and short brushes for the smoke shelf and smoke chamber walls, small brushes for damper frames, and mirrors and lights for looking around corners. On a stove, the baffle and burn tubes may need hand cleaning.

Cameras: the tool that checks the others

A chimney camera on a flexible rod or cable shows the inside of the flue before and after sweeping. Before, it shows how much buildup there is and whether anything, such as a cracked tile or a liner gap, changes the method. After, it shows whether the method worked and gives a clear view of the lining, which is often impossible under deposits.

For a Level 2 inspection, CSIA expects every flue liner's inner surfaces and joints to be examined, by video or another method. We start each visit with an assessment, run a camera wherever the flue permits, and hand over findings with photos. When cleaning reveals damage, the next step is a repair decision. See what a chimney camera inspection shows and flue resurfacing vs. a new liner.

Questions homeowners ask

Sources

1. Chimney Safety Institute of America: Homeowner resources (creosote and its removal)
2. Chimney Safety Institute of America: Frequently asked questions (creosote removers)
3. Chimney Safety Institute of America: Annual service of your oil-fired appliance chimney
4. Chimney Safety Institute of America: Chimney inspection levels
5. DuraVent: DuraTech Premium chimney installation instructions (PDF)
6. DuraVent: DuraLiner installation instructions (PDF)

This guide is general information. It can't diagnose a specific chimney; an inspection can.