In steam-heating systems, water is heated to its boiling point (212º Fahrenheit), and steam rises by convection through pipes to radiators located throughout the house. The steam releases heat into the air, then condenses; gravity sends the water back to the boiler for reheating. In a one-pipe system, the same pipe distributes steam to various radiators and carries the condensate back to the boiler. In a two-pipe system, one pipe supplies the steam, and the other returns the condensate to the boiler.

No matter what type of system, the boiler is the star of the show—a steam-heating system is only as good as its boiler. Luckily, a boiler can last 50 years—even longer given regular maintenance and care. Below are a list of key monthly and yearly maintenance issues—some you should call in a professional for, and others you can do yourself (depending, of course, on your level of comfort with the task). If your home has steam heat, chances are many others in the neighborhood do too, so if you’ve just moved to the area, ask your neighbors about the best boiler service people in town—then keep these five maintenance guidelines in mind:

1. Test the pressure-relief valve every month during the heating season by depressing the handle (located on top of the boiler, this valve allows steam to escape if the pressure in the boiler exceeds a preset safe level). If no steam comes out or the valve does not completely close, call a professional to have the valve replaced. It’s critical that this valve always be functioning properly.

2. Have a professional drain the boiler once a year. (To drain the boiler, a hose is typically attached to the boiler when it’s cold, and water is led into a floor drain, while the boiler’s interior is flushed with fresh water. This is best left to a professional).

3. Make sure the pressure of the boiler is always between two-10 psi. If the steam-pressure gauge indicator on the boiler is not in this range, call for service.

4. Open the boiler’s blowoff valve (at the bottom of the low-water cutoff) once a month when the system is off, to drain out all the sludgy water that could clog the whole system.

5. Open the valves at each end of the boiler’s steam-pressure gauge once a month. The water level should be in the middle of the valve. If water is not visible, shut off the boiler, let it cool, open the fill valve on the water inlet pipe and add water. If your system has an automatic water fill valve, call a service professional.

Finally: While the boiler needs the most maintenance and care, it’s important to keep the radiators in good shape too. In order to retain heat and operate efficiently, most steam pipes are covered with insulation (used as a heat shield, around and under the radiator cover). Never tamper with this insulation. Visually check the condition of what you can see; if it looks excessively cracked, dry or crumbling, have it serviced or replaced. Never add, remove or change existing insulation yourself, as doing it wrong can present a severe fire hazard; always call a professional. If you’re in the home-buying process: when it’s time for the home-inspection, choose an experienced, professionally trained home inspector who is familiar with steam-heating systems and can accurately evaluate the condition of the existing boiler and radiators.