Thermostats Illegal in Garbage & Drains Contains Mercury Hazardous Waste How to Check for Mercury Remove the thermostat’s cover and check if you see a bulb or vial that contains a silver, metallic liquid. This silver, metallic liquid is mercury. Do Not Throw in the Trash A thermostat that contains mercury should be disposed of as Household Hazardous Waste (HHW), so never throw them in the trash. Digital Thermostats Are E-Waste Digital thermostats should be disposed of as e-waste. Ways to Reduce Replace Mercury Thermostats Most thermostats nowadays are made without mercury, so they are less damaging to the environment and more energy efficient. Consider updating your thermostat to save energy and money.