Tools & materials
- Correct-size furnace filter (size is printed on the old one)
- Radiator bleed key
- Rag and small cup
- Marker
Step by step
- Step 1
Turn the thermostat off. Slide out the old furnace filter and read the size printed on its frame.
- Step 2
Insert the new filter with the airflow arrow pointing toward the furnace (away from the return duct). Write the date on it.
- Step 3
Turn the heat back on. Change 1-inch filters every 1–3 months and 4-inch filters every 6–12 months.
- Step 4
For radiators: with the heat running, hold a rag and cup under the bleed valve at the top corner.
- Step 5
Turn the bleed key counterclockwise a quarter turn until you hear hissing. Close it as soon as water appears.
- Step 6
Check the boiler pressure gauge after bleeding several radiators. Most homes run 12–15 PSI.
When to stop and call ProFix
If you see any of these, stop and call us:
- Boiler pressure stays low or goes above 25–30 PSI
- The furnace short-cycles or won't light
- You smell gas (leave the home and call the gas company first)
- Radiators stay cold after bleeding
Not in the mood to DIY? A ProFix pro can handle it for you in Chicago Metro and Dallas–Fort Worth, with a written price before work starts.
Related guides
These guides are general information for simple repairs. You're responsible for your own safety and for following local codes and your lease or HOA rules. When in doubt, stop and call a licensed professional. All DIY guides