CT Building Code Loophole Puts Homes at Carbon Monoxide Risk
A single word in Connecticut's building code lets installers use unsafe PVC pipe for furnace venting, creating a deadly carbon monoxide risk in homes.
Connecticut’s building code contains a single word that may be quietly putting lives at risk inside homes across the state. That word is “or.”
Current rules governing how furnaces and water heaters are vented give installers a choice: follow manufacturer instructions or use a certified safety standard. That flexibility has created a loophole allowing the use of cheap plastic piping that was never designed to carry dangerous exhaust gases. A proposed change to the 2026 Connecticut State Building Code would close it.
The risk is concentrated in high-efficiency heating systems, which have grown common in Connecticut homes over the past two decades. These systems save energy and cut utility bills, but they produce exhaust that must be safely carried out of the building. For years, many installers have used standard PVC pipe to do that job. PVC is the same material used in drain lines, and the standards governing it explicitly state it is not intended for venting combustion gases. Pipe manufacturers won’t recommend it for this purpose and won’t warranty it.
When these systems fail, the consequences can be fatal. Carbon monoxide is invisible, odorless, and lethal. The CDC reports more than 400 Americans die annually from unintentional CO poisoning, more than 100,000 visit emergency rooms, and more than 14,000 are hospitalized. More than half of those deaths occur at home. The Consumer Product Safety Commission has found that 84 percent of consumer-product CO deaths happen between September and April, exactly when Connecticut furnaces are running hardest. Failures can occur inside walls or ceilings, invisible until someone gets sick or worse.
The reason this problem has persisted is straightforward: safer materials cost more. If one manufacturer requires better venting, their systems become more expensive to install. In a competitive market, that creates a disadvantage, so the industry defaults to the cheaper option. Building codes exist precisely to break this dynamic. When a requirement applies equally to everyone, no company takes a competitive hit for doing the right thing.
Connecticut would not be acting alone. Massachusetts already restricts plastic venting to only CPVC, polypropylene, and materials specifically approved for combustion gas exhaust. Standard PVC does not qualify under those rules. Canada made comparable changes after documented system failures. In both cases, the market adjusted and installations became safer.
The proposed fix for Connecticut is not complicated. It would replace the ambiguous “or” with a single clear requirement: venting materials must be tested and certified specifically for combustion gases. One sentence. One standard. No loophole.
The timing is urgent. The 2026 Connecticut State Building Code is moving through its final stages after a review process that began in January 2024. The Connecticut General Assembly approves the codes and sets implementation dates, meaning legislators will soon decide what gets included. Once adopted, the code governs construction across the state for years. This is not a technical dispute between engineers. It is a public safety question that lawmakers are in a position to answer right now.
Critics of stricter venting standards tend to focus on cost and disruption to existing installation practices. Those concerns are real but manageable. The materials that meet proper safety certifications are commercially available. Installers in Massachusetts and Canada have adapted. The upfront cost difference is modest compared to the liability exposure that comes with a system failure and the human cost that comes with CO poisoning.
Connecticut has a history of acting deliberately on building safety, sometimes too deliberately. The state has updated its fire codes, its electrical standards, and its energy efficiency requirements as evidence and technology evolved. Venting requirements deserve the same attention.
What makes this situation unusual is how simple the solution is. No new technology is required. No extended phase-in period is necessary. A code change that has already worked in neighboring states is available, and the window to include it in the 2026 code is closing. The General Assembly should make sure that window doesn’t close without action.