As an HVAC pro, chances are you've had service calls that are the result of "handiwork" from homeowners thinking they could fix a problem that really required a pro's expertise. Plumbers deal with this on a daily basis, with PEX and other plumbing supplies readily available at big box hardware stores, along with "helpful" videos online of how to DIY.

But, increasingly, HVAC pros are running into homeowner DIY debacles as well. So much so that there's a You Tube channel dedicated to showcasing the nightmare projects HVAC pros have to try to untangle when homeowners first try to do it themselves. The channel has 22 million hits and counting, to give you an idea of how common this problem is becoming.

What are the most common HVAC DIY projects for homeowners?

Replacing filters. This is one task homeowners can and should do themselves.

Installing new thermostats. With programmable thermostats available at any hardware store or online, many homeowners attempt to upgrade their old thermostats themselves. But, it's more complicated than it sounds and can easily result in faulty wiring and poor performance of the thermostat.

Cleaning ducts and vents. Tools are readily available to homeowners to clean their own ductwork and vents. But for optimal performance and safety, ducts and vents should be professionally cleaned each year.

None of these DIY projects should cause catastrophic damage. But when a homeowner tries to repair a furnace or AC unit on their own, they can run into real trouble. So can pros.

When homeowners try to do a pro's job, serious consequences can result. Here are a few key points to pass on to homeowners:

Voided warranty. Every pro knows it, but homeowners may not. Most, if not all, HVAC manufacturers specifically state that professional service, installation and repair is required or the warranty on the unit will be voided. That means when you come out to repair their DIY repair job, they will be paying out of pocket for it.

Code violations. This is another area of expertise for pros. HVAC units must comply with local codes and regulations. A homeowner tinkering with their own furnace or AC unit may well run afoul of those codes. It can cause damage and, down the road, problems if they try to sell their property.

Damage to the unit. If a homeowner is relying on, for example, a YouTube video for DIY instructions, they can do serious damage with any installation, modification, repair or other workaround they might be attempting. It's going to result in a service call at the least, complete system failure at the worst.

Safety. Electricity, wiring, refrigerants ... need we say more? People can be burned, come into contact with chemicals, get electrical shocks, or worse. Improper installation or sizing of ductwork can cause ventilation issues, leading to poor indoor air quality or even carbon monoxide leaks, which can happen when homeowners work on their furnace systems. Wiring errors can cause electrical fires. Improper usage of refrigerants can lead to system inefficiencies or worse.

Missing efficiency standards rebates. Many homeowners don't know about the Inflation Reduction Act (IRA) that went into effect this year (2023). Homeowners are eligible for a tax credit of 30% of the cost, up to $2,000, for qualified AC, furnace, and heat pump units. Tampering with them via DIY may negate those benefits.

All of that said, you're still going to get service calls to fix DIY projects gone wrong. Here's how to handle going into a DIY fix situation.

Get the full information on the attempted DIY. This is vital. Ask the homeowner to be honest about what the original problem was and what he or she has already tried to do to fix it. Armed with full information, your job will be that much easier.

Take notes and photographs. There's an old saying in diplomacy: Trust, but verify. This applies here. When going into a DIY fix, take photographs of the homeowner's handiwork before you touch it. And take careful notes when they're explaining the original problem and their attempted fix. That way, you'll have proof that you didn't cause the problem.

Scolding vs. education. It's much better for your ongoing relationship with this customer to be educational, sympathetic and understanding. Explain the damages and dangers of attempting HVAC DIY. Let the homeowner know it's a job for professionals, you have their backs and you'll be there the next time they need a fix.

Explain the voided warranty. Homeowners may not know that their attempted DIY has voided their warranty. Those extra costs, especially if they have to replace the unit entirely, may be hard for them to swallow.

Dealing with homeowner DIY snafus is increasingly part of the job of an HVAC pro. With these tips, fixing their "fixes" will be quicker and easier.