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Plumbing, HVAC & Electrical Glossary.
Plain-language definitions for the plumbing, heating, cooling, and electrical terms Colorado homeowners come across most often. No jargon — just what each term means and why it might matter for your home.
A A
- AFCI Arc Fault Circuit Interrupter
- A type of circuit breaker that detects dangerous electrical arcs (often the source of home electrical fires) and shuts off power before damage occurs. Required by modern electrical code in many room circuits.
- AFUE Annual Fuel Utilization Efficiency
- The efficiency rating of a furnace or boiler. A 95% AFUE furnace converts 95% of its fuel into usable heat — the remaining 5% goes out the flue. Most new high-efficiency Colorado furnaces sit between 90% and 98%.
- Air Handler
- The indoor component of a split HVAC system. It moves conditioned air through the ductwork. In a furnace setup it's part of the furnace; with a heat pump or ductless system it's a separate component.
- Amp Ampere
- The unit of measure for electrical current. Most modern homes have a 200-amp service panel, though older homes may have 100 amps or less. EV chargers and large electrical loads sometimes require a panel upgrade.
- Anode Rod
- A metal rod inside a tank water heater that corrodes instead of the tank walls. Replacing the anode rod every 3–5 years can double the life of the water heater.
B B
- Backflow Preventer
- A plumbing device that prevents contaminated water from flowing backward into the clean water supply. Required on irrigation systems and some fixtures.
- BTU British Thermal Unit
- The standard measure of heat energy. Furnaces, AC units, and heat pumps are sized in BTUs per hour. A 60,000 BTU furnace, for example, can move 60,000 BTUs of heat into the home every hour.
- Breaker Circuit Breaker
- A switch in the electrical panel that automatically shuts off power if a circuit draws too much current. Breakers protect the wiring from overheating.
C C
- Capacitor
- A component in HVAC systems that stores and releases electrical energy to start motors. A failed capacitor is one of the most common AC repair issues.
- Condenser
- The outdoor unit of a central AC system or heat pump. It releases heat from your home into the outdoor air.
- Contactor
- An electrical switch inside HVAC equipment that controls the flow of power to the compressor and fan motor. A common failure point in older AC systems.
D D
- Drain Field
- A network of underground pipes that disperses treated wastewater from a septic tank into the soil. Not used with municipal sewer service.
- Ductless Mini-Split
- An HVAC system with an outdoor compressor and one or more indoor air handlers. No ductwork required. Good for additions, finished basements, or homes without existing ducts.
E E
- Evaporator Coil
- The indoor coil in a central AC or heat pump. Refrigerant evaporates inside the coil, absorbing heat from the indoor air. Usually installed above the furnace.
- Expansion Tank
- A small tank attached to a water heater that absorbs pressure changes as water heats and expands. Protects pipes and fittings from pressure damage.
F F
- Flame Sensor
- A small metal rod in a furnace that confirms the flame is lit. When it gets dirty, it loses sensitivity and the furnace may short-cycle or shut down. One of the most common Colorado-winter heating service calls.
- FOG Fats, Oils, Grease
- The cooking byproducts that should never go down a drain. FOG solidifies in pipes and is a leading cause of clogs and sewer backups.
G G
- GFCI Ground Fault Circuit Interrupter
- A specialized outlet or breaker that shuts off power when it detects a ground fault (often from water or skin contact). Required by code in kitchens, bathrooms, garages, and outdoor outlets.
- GPF Gallons Per Flush
- The water usage of a toilet per flush. Modern low-flow toilets use 1.28 GPF or less. Older toilets can use 3.5+ GPF — a significant water-bill difference over time.
H H
- Heat Pump
- A system that transfers heat instead of generating it — moving heat from outdoors into your home in winter, and from indoors to outside in summer. Modern cold-climate heat pumps work effectively in Colorado winters and are increasingly popular as an alternative to gas furnaces.
- HRV / ERV Heat / Energy Recovery Ventilator
- A device that brings fresh outside air into the home while capturing the heat (or in summer, cool) from the air being exhausted. Useful for tightly-sealed modern homes.
- Humidifier
- A device that adds moisture to dry indoor air. Whole-home humidifiers attach to the HVAC ductwork. Especially relevant in Colorado, where indoor humidity often drops below 20% in winter.
M M
- MERV Rating Minimum Efficiency Reporting Value
- The filtration rating of an air filter. Higher MERV catches more particles but restricts airflow more. Most residential HVAC systems run best with MERV 8–13.
- Main Water Shutoff
- The valve where the entire home's water supply can be shut off in an emergency. Every homeowner should know where their main shutoff is — it can prevent thousands of dollars in damage during a burst pipe.
P P
- Panel Electrical / Service Panel
- The metal box (often in a basement or utility room) where electrical service from the utility enters the home and is distributed to circuit breakers. Older homes often have undersized panels that benefit from upgrades.
- PEX Cross-linked Polyethylene
- A flexible plastic plumbing pipe used as a modern alternative to copper. Less prone to freezing damage and easier to install in retrofits.
- Pressure Regulator
- A valve that reduces incoming municipal water pressure to a safe level for your home's plumbing. Typical residential setting is 50–60 psi.
- PVC Polyvinyl Chloride
- A rigid white plastic pipe most often used for drain, waste, and vent lines, plus some cold-water supply runs.
R R
- Refrigerant
- The chemical inside an AC or heat pump system that absorbs and releases heat as it cycles between liquid and gas. Older systems used R-22; modern systems use R-410A or newer.
- Repipe
- Replacing the water supply pipes throughout a home — usually because the original galvanized steel pipes have corroded or the home has had repeated leaks. See Smith repiping service.
S S
- SEER Seasonal Energy Efficiency Ratio
- The efficiency rating of an AC system. Higher SEER means lower energy use for the same cooling output. New systems in Colorado typically range from SEER 14 (entry) to SEER 22+ (premium).
- Slab Leak
- A water leak in a pipe running underneath the home's concrete foundation slab. Often signaled by unexplained hot floors, water bill spikes, or the sound of running water. Slab leak detection is a specialty service.
- Short Cycling
- When an HVAC system turns on and off rapidly without completing a full heating or cooling cycle. Causes premature wear and uneven temperatures. Often caused by oversized equipment, airflow problems, or sensor issues.
- Sump Pump
- A pump installed in a basement pit that automatically removes accumulating water — protects against basement flooding from groundwater or heavy rain.
T T
- Tankless Water Heater
- A water heater that heats water on demand instead of storing hot water in a tank. Uses less energy, lasts longer, and provides "unlimited" hot water — but has a higher upfront cost.
- Thermostat
- The controller that tells your HVAC system when to run. Modern smart thermostats can learn schedules, integrate with monitoring, and reduce energy use significantly.
U U
- UV Air Purifier
- A device installed in HVAC ductwork that uses ultraviolet light to kill mold, bacteria, and viruses passing through the system. Often paired with high-MERV filtration.
V V
- Variable-Speed System
- HVAC equipment that can run at multiple output levels rather than just on/off. Quieter, more efficient, and provides more consistent comfort than single-stage equipment.
W W
- Water Hammer
- A loud banging sound in pipes when water flow stops suddenly. Can damage plumbing over time. Usually fixed with arrestors or pressure adjustments.
- Water Softener
- A treatment system that removes hardness minerals (calcium, magnesium) from incoming water. Reduces scale buildup in fixtures, extends water heater life, and improves cleaning. Especially relevant for Colorado Front Range homes with hard water.
Glossary growing
This glossary covers the most common terms Colorado homeowners encounter. We'll keep adding as Smith fields new questions. If a term isn't here, send Smith a message and we'll add it.