Debris at a chimney cleanout (C) Daniel Friedman Chimney Cleanout Door Inspect & Fix
How to repair a damaged, leaky chimney cleanout

  • CHIMNEY CLEANOUT DOORS - CONTENTS: A guide to chimney cleanout doors and access ports - What to look for at the chimney cleanout door to detect problems with a chimney flue interior; Masonry fragments in the chimney cleanout can indicate flue damage;
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Chimney cleanout doors & openings:

This article describes chimney cleanout access doors or ports. We explain that in addition to using the chimney cleanout as a service port to remove debris that has fallen to the bottom of a masonry chimney, the cleanout door and the type of debris found inside can tell us something about the condition of the chimney flue even though we cannot see most of it.

These articles on chimneys and chimney safety provide detailed suggestions describing how to perform a thorough visual inspection of chimneys for safety and other defects. Chimney inspection methods and chimney repair methods are also discussed.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

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Chimney Flue View by Cleanout Door

Water leak in chimney out at cleanout door (C) Daniel Friedman

Article Series Contents

Where you can find a chimney cleanout or can remove a flue vent connector to look into a flue, use of a mirror inside the flue to view the flue from below.

[Click to enlarge any image]

This is by no means a thorough and accurate view of all of the chimney flue interior. But if the chimney was constructed as a straight flue up through the building roof, you should see daylight - otherwise the flue has become blocked, perhaps with nesting animals or collapsing debris.

Our photo (left) will provide an easy view into this section of the chimney flue. But even before opening the chimney cleanout door we can see that there has been a history of leaks inside of the chimney flue.

Chimney Cleanout Door Inspection & Hazards

Chimney Cleanouts Are Required

All chimneys must have a cleanout at least 12" below the lowest appliance inlet opening. A fireplace is considered as access for cleaning. Cleanouts must have metal or pre cast concrete doors that can be secured tightly

Photograph of a chimney cleanout door (missing) Missing chimney cleanout door (C) Daniel Friedman

In the photo at above left, the chimney cleanout is easy to find and the door is in place and closed; look inside for clues of flue damage and also for the presence of a flue liner if this is a single-brick wythe flue.

In the photo at above right the home made cleanout door was a metal scrap propped against the chimney. It has fallen open, and we see some masonry debris that has fallen down the flue.

Chimney cleanout door found ajar (C) Daniel Friedman

Chimney cleanout door left open

We found this chimney cleanout door (shown above) ajar.

This chimney cleanout access port served a common ash dump below both a fireplace flue and a separate heating appliance chimney flue.

Watch out: Failure to close the chimney cleanout door can result in a fire and will certainly interfere with good draft in the flue. A rusted-out chimney cleanout door and its role in producing potentially dangerous carbon monoxide at the heating equipment is discussed later in this article.

Water leaks through the chimney cleanout port

We found this chimney cleanout pouring water into the building basement during a heavy rainstorm.

Water pouring into basement through chimney cleanout (C) Daniel Friedman

See CHIMNEY CAP & CROWN DEFINITIONS for chimney top sources of water leakage.

But in the case of the water leak shown our photo most likely the water source is from roof spillage onto the ground or surface runoff on the ground around the chimney base.

A combination of in-slope grade around the chimney base and leaks into the chimney can be detected by noticing water or creosote leak stains around the chimney cleanout opening even if you don't have the good luck to catch water in the act of entering the building.

Water leak stains at the chimney cleanout door (C) Daniel Friedman

Our photo above illustrates this condition - brown rust and creosote stains below the cleanout access opening. This chimney and its rain cap and cap seal need further inspection as may the flue itself.

Watch out: water damage to a chimney flue may leave the chimney unsafe.

Combustibles Stuffed in Chimney Opening

Using a one-gallon plastic bottle (photo below) as a means of sealing off a chimney cleanout opening (photo at left, Poughkeepsie, NY) is nothing less than stupid.

Chimney cleanout door made from plastic bottle (C) Daniel Friedman

The fire hazard is greater below a fireplace where burning embers may fall into the cleanout pit, but this expedient is not recommended in any case.

Do not use a combustible material in the construction of chimneys or flues.

Masonry Fragments and Debris at the Chimney Cleanout May Indicate an Unsafe Chimney

Debris at a chimney cleanout (C) Daniel Friedman

Masonry Flues & Clay Tile Lined Flues: If you open a chimney cleanout-door or pull the flue vent connector from a dead end chimney flue, in either case you are looking at the very bottom of the chimney flue. If you are inspecting a masonry chimney, be alert for discovery of masonry fragments when inspecting or cleaning the bottom of the flue.

If a piece of brick, masonry block, concrete, or clay flue tile liner is pulled out of your chimney, ask "where do you suppose this came from?" If the masonry scrap fell during construction of the chimney it may mean nothing.

But if it fell because the chimney has been damaged, perhaps by water, frost, or during cleaning, then you probably have an unsafe chimney flue - more investigation is in order, promptly.

Certainly if you believe that the masonry scrap found at the bottom of a flue fell during original construction, and if you remove it during cleaning, you should never find another piece in the flue bottom.

If you do, the flue has been damaged anew and it is unsafe

Our photo shows normal chimney creosote and debris at the bottom of a flue. When removing this material be alert for surprises such as fragments of clay flue tile liner.

Chimney Cleanout Door Must be Accessible

Chimney cleanout door blocked (C) Daniel Friedman

If the chimney cleanout access door is blocked such as by an installed appliance (a water heater in our photo at left) how is someone going to access the flue for inspection or cleanout?

Wait a minute? What's that sitting on the horizontal surface at the top of our photo?

Has an abandoned chimney been partly removed? It is possible that this is an offset access into a common ash pit.

In some constructions multiple chimney flues may terminate in a single large ash pit with one or more individual cleanout doors.

We suspect that this is an improper design, making regulation of draft among the chimneys difficult, since any individual flue that begins to draw may pull air down and into itself from a neighbor

Home made chimney cleanout door closures

If the chimney cleanout door is closed using a permanently-mounted component such as shown in our photo you've got a clue that work was not done by a professional.

Improper chimney cleanout door opening closure (C) Daniel Friedman

This chimney cleanout closure may be fireproof (really?) and it may stop a draft problem, but it violates the readily-accessible and operable chimney cleanout door requirement.

Chimney Cleanouts on Metal Flues

Factory built metalbetos chimney cleanout during installation (C) Daniel FriedmanCleanout opening on a metal chimney for an oil fired boiler

Even a factory-built insulated metal chimney needs to include a cleanout access port.

Here, shown during installation, you can see that this metal chimney includes a removable cleanout door at the bottom of the tee used to turn from horizontal to vertical in the chimney run. This metal chimney vents an oil fired heating boiler. The horizontal tee connects through the wall to a boiler on the other side.

The bottom cap on this chimney could be removed to give a straight-line vertical access into the metal chimney for cleaning or inspection.

This photo of a metal chimney cleanout port was taken during construction - the required drywall (and an access cover through the drywall if the chimney is enclosed) were not yet installed.

Watch out: opening a cleanout at the bottom of a vertical chimney run like this can spill a horrible mess of ash and debris - be prepared, or better, if the horizontal run to the tee is short, vacuum and clean the chimney first through the horizontal chimney run.

In practice this particular tee-bottom cleanout is never used. The horizontal run through the wall is less than two feet. During oil burner cleaning and service the oil heat technician removes the boiler's flue-vent connector and vacuums out this chimney base through the wall. That avoids spilling soot all over the clothes in the closet.

Cleanout access on a metal chimney for a wood stove

Metalbestos chimney cleanout tee installation details (C) adapated  from Metalbestos chimneys cited in this article

Above in an illustration of a cleanout tee installed in a metal chimney, adapted from information from Metalbestos, the cleanout tee sketch can be confusing so let's elaborate for a wood stove installation.

First you would not install an uninsulated metal chimney or flue vent connector within 36" of a wood frame ceiling (as might be implied in the sketch) though you might be ok with a class A chimney.

Second, which opening is the "cleanout" ?

The black opening gives access to the chimney but I'd prefer to see this tee much lower in the indoor space, right at the woodstove.

Provided there is enough clearance above the floor to access the chimney base, I'd tee the wood stove into the black opening - the horizontal connection, and I'd prefer to use the bottom opening as the cleanout.

Watch out: as I warned above, don't open the bottom cleanout opening on a metal flue without first taking care to control where the falling ash and soot will go.

Also see CLASS A CHIMNEYS, MetalBestos™

Missing Chimney Cleanout Door & Other Chimney Cleanout Opening Hazards

What if there is no cleanout on the woodstove flue?

Paul Galow's Jotul woodstove cleanout (C) Daniel Friedman at

Above, my friend Paul Galow installed this Jotul woodstove - I traded it to him for a Seiko wristwatch - in his New York home.

The black metal flue uses a 90 degree elbow to connect to the vertical riser that's going to pass into an insulated flue that goes through the roof structure.

There is no cleanout door at all. To clean this flue Mr. Galow simply disconnects the elbow from both the wood stove and from the vertical flue section.

Watch out: be sure that the metal chimney is easily accessible for regular inspection and cleaning, either by simple disassembly or through a cleanout opening. Making it inconvenient to inspect and clean a chimney means that this important safety task won't get done. The risk is a fatal building fire.

Creosote removed from a wood stove metal flue (C) Daniel Friedman at

That cleaning this metal flue is a critical safety step is pretty obvious when you see the clots of creosote that we retrieved from the flue. Setting accumulated creosote on fire in a chimney results in a very hot chimney fire that is likely to take down the structure.

Metal woodstove chimney with no cleanout

Above: a metal chimney serving a woodstove in an antiques barn along Highway 61, south of Two Harbors, Minnesota. We see three 90's, a rather short flue close top the roof edge, and no cleanout opening.

Paraphrasing Bob Dylan,

Where in hell was that chimney done? God said, "Out on Highway 61"

Openings at the chimney base around the cleanout door

Photograph of a chimney cleanout door (missing) .In this photo the chimney cleanout is easy to find but isn't that door missing? No not in the first photo at left of this pair of photographs of chimney cleanout doors.

But look carefully at the next photo given below.

Even though a cleanout door is installed, masonry has fallen out above the door, giving an opening right into the flue.

A missing chimney cleanout door or any other hole in the flue means that there is a fire safety hazard (sparks or ashes falling out onto the basement floor) and also that it is impossible to control the draft in the flue.

Watch out: Where the hole in a chimney is lower than or below the flue vent connector joining the heating appliance to the flue, there is also a serious problem with draft control as well as the risk of sparks or embers falling out of the flue into the interior of the building where they may cause a fire.

Where you can find a chimney cleanout or can remove a flue vent connector to look into a flue, use of a mirror inside the flue to view the flue from below.

This is by no means a thorough and accurate view of all of the chimney flue interior.

But if the chimney was constructed as a straight flue up through the building roof, you should see daylight - otherwise the flue has become blocked, perhaps with nesting animals or collapsing debris.

We have found heating boilers with draft problems and "repair attempts" like removing the boiler's barometric damper, when all the while the root problem of bad chimney draft was that the cleanout door was open or missing.

Chimney blockeds by debris (C) Daniel Friedman

Watch out: Our photo shows a chimney thimble completely blocked by falling debris. If you find this much trash at the bottom of your chimney or at any other chimney opening, you need an expert to evaluate the chimney condition and safety as soon as possible.

The chunks of masonry debris make it likely that the chimney in our photo at left is in very poor condition and is unsafe.

How to Seal a Leaky Chimney Cleanout Door

Replaced chimney cleanout door (C) Daniel FriedmanReader Question: can I fill in the old chimney to stop drafts?

11/29/2014 Dazy said:

I have a gas insert now in my old fireplace. May I , and how can I fill the old chimney cleanout because I get a lot of cold draft from it?

Reply: Sealing the Cleanout Door on an Abandoned Chimney

Above: an outdoor chimney cleanout door in good condition but sporting a clue (stains at the door bottom) that water has been running down this chimney interior: there is a risk of hidden damage and of an unsafe flue.


If there is not already a screened chimney cap over the flue serving the abandoned fireplace, and if there is safe easy access to the rooftop or if you can arrange for service by a chimney sweep, placing a solid cover over the chimney top has the advantage of keeping animals from nesting in the chimney and also protecting it from future rain and water damage.

From inside the fireplace be sure that the fireplace damper is un-damaged (not broken, missing, perforated by rust) and place it in the closed position.

At the chimney cleanout door some readers describe using a high temperature silicone sealant (caulk) or high temperature refractory cement to seal off the door. I appreciate the inclination for that simple approach but worry that some work would be needed in the future should it be necessary to return the old flue to service or to access and clean out the chimney base.

If you do decide to seal around the door, clean the surfaces of loose rust and dirt. Then wipe the surfaces clean of remaining dust before applying your bead of high temperature silicone exterior grade sealant around the edges of the cleanout door. That way the sealant can be easily cut away if future access is needed.

Watch out: be sure that your new gas-fueled fireplace insert is installed according to the manufacturer's specifications, all of them, including provision of combustion air and as required, exhaust. A gas fireplace that is not properly installed can produce dangerous, even fatal carbon monoxide gas. Be sure that you have working CO detectors properly installed.

Seal a Leaky Chimney Cleanout Door where the Flues are In Use

Metal tape repair on rust-damaged chimney cleanout door (C) Daniel FriedmanWatch out: before sealing a chimney cleanout door shut, be sure that the door serves only the chimney or flue that is being abandoned. Do not use sealant to caulk-shut the cleanout door of a chimney that is in active use, as you'll need to be able to open the door later to inspect or clean the chimney base.

Some chimneys use a common cleanout area in the base of a chimney that contains multiple flues.

In that case that's another reason that you can't seal the door as it is still needed. But you can improve the cleanout-door's sealing closure by making sure it fits tightly and if necessary adding a thin coating of silicone on the door face and its meeting surface on the door frame. Let the silicone sealant dry on those surfaces before closing the door and returning the chimney to service.

Above: we used multiple layers of metal adhesive-backed tape to seal the bottom of this rust-damaged chimney cleanout door on a home in Two Harbors Minnesota.

Watch out: a previous heating system inspection by a heating service company had condemned the home's cast-iron gas fired heating boiler because the inspector detected a trace of carbon monoxide (CO) gas spillage at the boiler flue draft-hood.

More-happily, working together with another service technician from the same company we found that behind the boiler the cleanout door for the boiler's chimney flue was ajar and that the chimney cleanout door itself was rust-perforated.

Combined with servicing and cleaning the boiler we cleaned out years of soot and crud from the bottom of this flue, repaired the door with multiple layers of metal tape, and closed the cleanout. The carbon monoxide gas hazard completely disappeared and the boiler was saved to heat another day.


Continue reading at CHIMNEY CLEANOUT CLEARANCE to COMBUSTIBLES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see CHIMNEY CLEANOUT DOOR FAQs - questions & answers posted originally at this article

Or see DRAFT REGULATOR SOOT INSPECTION for another spot where it may be possible to inspect for clues about the condition of a chimney and its safety.

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CHIMNEY CLEANOUT DOOR at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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