This article was produced in partnership with The Home Depot

Your limits know no bounds—but they probably should. Because when it comes to home improvement, there are a few key jobs that really do require a special kind of expert. Tackle them without truly knowing what you’re doing and you could make things much, much worse—or even put you and your family at risk. Enter The Home Depot.

In addition to all the experienced staffers who man the floor to help you find your DIY supplies, The Home Depot also works with lots of pros and local experts, who are vetted and highly trained in their fields. We spoke with some of those professionals to make a short list of those do-not-try-yourself projects better left to the experts.

Here are three things you should never try to fix yourself—and who you should call instead.

1. HVAC Systems

Do you know how to check for a failing capacitor? How to detect a refrigerant leak in your evaporator coil? Or how to check and properly adjust refrigerant levels? These are not things you can reliably look up on YouTube. In fact, most maintenance and repair items require specific tools, training, and certifications—and working on your own system could possibly void your warranty. Most systems have a lifespan of 10 to 15 years. As they get older, their efficiency can decrease dramatically, and critical components can wear and fail.

“If your system is always running, constantly turning on and off, making strange noises, smells funny, or just isn’t keeping you comfortable—these are all warning signs of potential issues,” says Viviane Essex, national install merchant for HVAC systems at The Home Depot. Some pros say you should never spend a certain amount on a repair for an older system, or that systems over a certain age need to be replaced, but according to Essex: “When you need repairs every year, or the cost of a repair times the age of your system is more than $5,000, it’s probably time to trade things in.”

To help you with HVAC system maintenance, repairs, or replacement, The Home Depot works with local authorized service providers who meet strict standards for value, professionalism, expertise, and customer service. They must undergo thorough background checks for your peace of mind. One thing to note is that unlike many common online pro service sites (like Angie’s List, Home Advisor, etc.), your HVAC transactions are directly handled by The Home Depot, installed and serviced by its local authorized service providers. The Home Depot backs all its heating and cooling installations with a one-year warranty, and repairs and tune-up services have a 90-day guarantee.

2. Water Heaters

Those warning stickers on your water heater are there for a reason. Changing your hot water heater calls for a working knowledge of plumbing, electrical work, ventilation, local building codes, and more. And if you attempt to fix or replace yours without a full understanding of how things work, there could be some catastrophic results: You could void your warranty, install the wrong tank, cause a combustion, have a carbon monoxide issue, or something much worse.

The Home Depot’s water heater installers are licensed, insured, and fully vetted. To get matched with one, just enter your zip code, fill out a brief questionnaire to identify the problem, and pick three preferred dates and times for an at-home visit. Same-day water heater installation is available during the week in most locations, if you request service before noon and live within 30 miles of a Home Depot store. Plus, all water heater installation services are backed with a one-year warranty on parts and labor, just in case.

3. Windows

While plenty of people handle their own window installations, it’s not recommended for the mildly handy, mainly because windows are cumbersome and fragile. And if you need a full-frame window installation, things get a lot more complicated. (The last thing you want is to install a bunch of new windows, only to realize on the first cool night you didn’t seal things properly.)

Once again, The Home Depot works with its in-house pros through its window installation service. You can sign up for a free in-home or virtual consultation, then be presented with options and a free quote. “Our experts help shoppers pick windows rated for their area of the country,” says Karla Thompson, merchant for windows and doors at The Home Depot. “They can suggest the right type of glass and best type of window for every need.” Your pro can also calculate the potential energy savings you can expect from new windows, as well as how much your home value may increase as a result.

Once you pick your windows, The Home Depot will handle the installation. You can feel confident you’re in good hands: All window replacement and installation services are backed with a robust and competitive warranty.

The Home Depot is licensed and stands behind its installation work. Learn more here.

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