Level 1 sweep and inspection to the NFPA 211 annual standard - flue, crown, cap, and flashing checked and photographed
Chimney sweep logs do not sweep chimneys. They loosen some creosote - which then falls where a brush and vacuum still have to collect it.
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AfterDuraFlex Flue Liner Replacement: The Fairfax Owner’s Guide
DuraFlex flue liner replacement in Fairfax typically runs $1,900 to $4,200 installed, depending on the liner diameter, the height of your flue, and whether we’re pulling the old liner out of a straight run or fighting a crooked one. We stock DuraFlex-compatible replacement liners and components on the truck, so most swaps go same-day once the measurements are confirmed. You usually find out you need this when a sweep’s camera shows a tear near a seam, or when your CO detector starts chirping and the old liner turns out to be the cause.
What brings most Fairfax homeowners to this page is simple: their existing DuraFlex liner has been in there ten or fifteen years, condensation or a chimney fire weakened a section, and now gas or wood heat is venting through a pipe that is no longer doing its one job. Wendell Pike has pulled more failed liners out of Fairfax chimneys than he can count, and the DuraFlex ones tend to fail in predictable ways. The good news: this is a fixable problem, and it is not a mystery. The bad news: it is not a parking-lot patch either.
Before you spend a dime, know this: not every distressed liner needs replacing. Sometimes the camera shows creosote buildup that looks worse than it is, and a thorough cleaning buys you another five years. If it does not need doing, we will tell you that too.
Which DuraFlex Models This Applies To
DuraFlex makes two main liner product lines that show up in Fairfax homes: the DuraFlex 316L (a flexible stainless alloy liner for gas and oil appliances) and the DuraFlex Al29-4C (a heavier flexible alloy rated for wood and pellet stoves, as well as higher-temperature gas units). There is also the DuraFlex Pro line, which uses a smoother corrugation profile and is sometimes specified for relining masonry chimneys with tighter bends. If your liner carries a DuraFlex label plate at the appliance connection, it is usually one of these three.
Here is the compatibility gotcha most owners miss: DuraFlex liners are sized to the inside diameter of the existing flue tile, not to the appliance collar alone. A 6-inch appliance outlet does not automatically mean you need a 6-inch liner. The liner has to fit inside the clay tile without kinking at offset joints, and in a lot of Fairfax homes built in the 1960s through 1980s, those offsets are where the old liner is already rubbing thin. We measure at three points before ordering or pulling a liner off the truck: the appliance outlet, the narrowest point in the flue, and the total vertical run. Get any of the three wrong and you have a liner that whistles, restricts draft, or fails early.
On the OEM versus aftermarket question: we install genuine DuraFlex replacement components when the existing system is salvageable and the liner itself is the only failed part. For full liner replacement, we also carry quality aftermarket equivalents that match the 316L and Al29-4C alloy specs and UL listings. We will tell you which one we are quoting and why. Top Hat Chimney is an independent local shop, not a DuraFlex dealer, so the recommendation is based on what is actually right for your chimney, not on what a manufacturer pushes.
Signs Your DuraFlex Flue Liner Replacement Is Failing
- Carbon monoxide detector trips with no obvious smoke. A cracked or separated liner lets combustion gases leak into wall cavities or living space before they ever reach the chimney cap. This is the one that matters most. Do not reset the detector and call it a bad sensor without checking the liner.
- Pilot light or gas burner keeps going out. When a liner deteriorates, it restricts draft. Appliances that used to hold a flame start dropping it. A struggling draft upstream of the liner is often mistaken for a bad thermocouple or gas valve issue.
- Rust-colored streaking or corrosion at the appliance connection. Condensation inside a failing liner drips back down and eats at the connector pipe. If you see reddish deposits around the collar, water is condensing where it should not be, and that points to liner cooling too fast or leaking.
- A metallic rattling sound when the flue heats up. Loose liner sections expand and contract against each other as temperatures cycle. That sound is a section at a misaligned seam flexing under heat stress, and it is one heating season away from a full separation.
- You see daylight gaps or feel cold air dropping into the firebox when the damper is open. A properly connected liner should be sealed end to end. Cold-air backdraft when the appliance is off means there is a breach somewhere in the system that is pulling room air the wrong direction.
Replacement Cost & What’s Included
In Fairfax, a full DuraFlex-compatible flue liner replacement typically lands between $1,900 and $4,200 installed. A straight single-story run with easy roof access sits at the lower end. A two-story liner with multiple offsets, or a job that requires removing and re-pouring a damaged crown, pushes toward the higher end. Here is the line-item picture:
| Item | Typical Fairfax Range |
|---|---|
| Liner material (316L or Al29-4C, based on appliance) | $800 - $1,600 |
| Connector, top plate, rain cap, and termination hardware | $300 - $600 |
| Removal of old liner and flue prep (cleaning, minor tile dressing) | $400 - $800 |
| Install labor and safety inspection | $400 - $1,200 |
What matters beyond the parts number is the warranty behind the work. Every liner we install in Fairfax falls under the 90-Day Done Right Promise. If the liner does not draft right, if the connection leaks, if anything about the install fails inside those 90 days, one call brings the crew back at no extra cost. That promise is in writing on the estimate, not in a verbal handshake.
We do not quote a liner job without dropping a camera down the flue first. The number you hear before the work is the number on the invoice, and we will show you the footage so you can see exactly why the old liner failed.
DIY or Call Us?
Here is the honest split. You can safely check the visible part of the liner at the appliance connection: look for rust streaking, loose clamp bands, and any gap between the liner and the connector pipe. That is diagnostic, not repair, and it is worth knowing what you are looking at before you make a call.
What you should not do is drop a liner yourself. This is a rooftop job on a Fairfax chimney, often with a steep pitch or a two-story ladder setup involved. A liner that kinks during installation, or a top plate that is not sealed correctly, turns a $2,500 repair into a $6,000 rebuild. We have watched homeowners fight this job on a Saturday and call us on Monday with a liner twisted like a corkscrew inside the flue. It is also flat-out dangerous: one slip on a wet asphalt shingle is a hospital visit, not a project. Wendell and his crew do this every week. The liner goes in straight, the cap goes on sealed, and the camera confirms it before we leave.
If you suspect your DuraFlex liner is done, call (571) 624-2385. We will give you a straight answer and a firm price before any tools come off the truck.
FAQs
A properly sized and installed DuraFlex liner in Fairfax typically lasts 15 to 20 years. The variable is moisture: Fairfax winters bring freeze-thaw cycles and humidity that accelerate condensation inside gas-fired liners. A liner that runs cooler because it is oversized for the appliance will condense more and fail in as few as 8 to 10 years. Get the sizing right and the liner earns its full life. Call (571) 624-2385 if you want the camera to tell you where your liner stands today.
Yes, if the damage is a single failed joint or a small tear near a connection. We sometimes splice in a replacement section using DuraFlex-compatible couplers and clamp bands. But if the alloy is perforated in multiple spots or the liner has collapsed at an offset, patching buys a season, not a solution. We will put the camera on it and tell you plainly which situation you have.
Most Fairfax liner replacements run 4 to 7 hours from setup to final camera check. That includes removing the old liner, brushing the flue, dropping the new liner, securing the top plate and cap, and testing draft at the appliance. Two-story homes and tough roof access add an hour or two, but it is still a single-day job in almost every case. Call (571) 624-2385 for a time window that actually holds.
We stock 316L and Al29-4C replacement liners in common diameters, plus connectors, top plates, caps, and clamp hardware on the service truck. If your Fairfax home needs an unusual size or a specialty termination, we can usually source it within two business days. You won’t wait three weeks for a liner. Call (571) 624-2385 and Wendell can tell you in five minutes whether your liner is on the truck or on order.
Get a straight answer on your DuraFlex liner in Fairfax
If you are looking at a failed DuraFlex liner and want real numbers, not a sales pitch, start with the camera. We will drop a scope down the flue, show you exactly what is wrong, and give you a written price before any work begins. If it turns out you just need a cleaning, that is what we will tell you, and that is all you will pay for.
Top Hat Chimney has been serving Fairfax since 1999, and we also stock parts for HeatShield and Gelco systems if that is what your home actually has. Call (571) 624-2385 for a free estimate. A live person answers, around the clock, and it might be Wendell himself.
Written by Wendell Pike, Owner, Top Hat Chimney at Top Hat Chimney, serving Fairfax and nearby areas.