Most of the chimneys I line in Pittsburgh started out venting an oil furnace, or a furnace and a water heater together. Then somewhere along the way the house switched to gas, and nobody touched the chimney. The trouble is the old clay tile flue was built for oil. It's the wrong size and the wrong material for gas. Gas burns cooler and wetter, and that moisture goes to work on a flue that isn't lined for it. If you're putting gas appliances on an old chimney, you need the right liner, and chimney liner installation is what I do every week around Pittsburgh.
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Why Gas Appliances Need the Right Chimney Liner
Here's what's going on inside that flue. An old clay tile liner sized for an oil furnace is too big for a modern gas appliance. Gas needs a smaller, properly sized flue to draft, meaning the exhaust actually rises and leaves the house. Drop a gas appliance into an oversized clay flue and the draft goes weak.
The bigger issue is moisture. Gas combustion runs cooler than oil and it's more acidic. In a flue that's too large or unlined, those gases cool down, condense on the walls, and turn into acidic water sitting against your masonry. That does two things. It rots the flue and the brick from the inside, and it sets up a carbon monoxide risk when the appliance can't vent the way it should. The fix is a stainless steel flexible liner, sized to the appliance and run from the top of the chimney down to the connector. Sized right, it drafts strong and keeps the moisture and the gases where they belong.
When Do You Need a New Liner?
Give me a call about a liner if any of these fit your house:
- You're replacing an oil furnace with a gas furnace.
- You just put in a new gas water heater and nobody has looked at the flue.
- Your clay tile liner is cracked, spalling, or breaking apart.
- Your chimney failed a Level 2 chimney inspection.
- You're installing a new gas insert or a wood stove.
- The HVAC company flagged your chimney during the appliance install.
- A home inspection noted the condition of your chimney liner.
What a Liner Job Actually Involves
When I come out, I start by looking at what you actually have. I check the size and condition of the existing clay tile, measure the flue, and look at the BTU rating of the appliance the liner needs to serve. Then I size a stainless steel liner to that appliance, not to a guess. I run the new liner down the flue, connect it to the furnace or water heater, seal the top with a cap and storm collar, and insulate it where the draft or condensation calls for it. Most jobs are done in a day. If the masonry itself is breaking down while I'm up there, that's chimney repair, and I handle that too. Before I call a liner job finished, I make sure it drafts and vents the way it should.
A Note on the Orphaned Water Heater
Here's a problem I run into all the time, and most homeowners have never heard of it. When you put in a new high-efficiency furnace, the kind that vents through a white PVC pipe out the side of the house, that furnace stops using the chimney completely. If your water heater is gas and still vents into the old flue, it's now in there alone.
That matters because the flue was sized for two appliances working together. With just the water heater left, the flue is far too big. A water heater on its own can't push its exhaust up an oversized, cold flue, so the draft stalls. In the worst case the combustion gases, carbon monoxide included, spill back into the house instead of going up and out. That's the orphaned water heater, and it's a real safety problem, not a maybe.
The fix is straightforward once someone catches it: a properly sized stainless liner for the water heater alone, so it drafts on its own. If you've had a high-efficiency furnace go in and nobody said a word about your water heater or your chimney, get it looked at.
Pittsburgh and the Surrounding Area
I do chimney liner work across Pittsburgh and the surrounding Allegheny County area, from the older city neighborhoods to the suburbs and the river towns. Most of this work is in the exact kind of older housing stock Pittsburgh is full of, where the chimney has been standing a lot longer than the gas appliances hooked to it. If your home is on gas and the chimney has some age on it, I can get to you. For a fireplace or wood stove instead of a gas appliance, that falls under my general chimney relining service.
HVAC and Plumbing Contractors
If your customer needs a liner before their new furnace or water heater is code compliant, call me directly. I size and install the liner fast, so your install passes inspection and your customer isn't left waiting on the chimney. I work clean, I'm local, and I keep it simple.