This comprehensive glossary covers plumbing, HVAC, and home mechanical systems terminology. Use it to understand service quotes, communicate more clearly with technicians, and make informed decisions about repairs and replacements. Terms are organized alphabetically and sourced from industry standards used by licensed contractors in Columbus, Ohio. Book a service call when you’re ready to act.
A
- Absorption Chiller
- A cooling system that uses heat energy (rather than electricity) to drive the refrigeration cycle. Common in commercial HVAC applications.
- Access Panel
- A removable section of wall, ceiling, or floor that provides access to plumbing, electrical, or HVAC components without major demolition.
- AFUE (Annual Fuel Utilization Efficiency)
- A measure of furnace efficiency — the percentage of fuel converted to heat. Modern high-efficiency furnaces reach 96–98% AFUE. Standard furnaces are 80% AFUE.
- Air Handler
- The indoor component of a split HVAC system containing the blower, evaporator coil, and filter. Circulates conditioned air throughout the ductwork.
- Air Lock
- A pocket of air trapped in a plumbing line that prevents water flow. Common in hot water systems after draining.
- Anode Rod
- A sacrificial metal rod inside a water heater tank that attracts corrosive minerals to protect the tank lining. Should be inspected every 3–5 years.
- Anti-Scald Valve
- A mixing valve that limits hot water temperature at fixtures to prevent burns. Required by code in showers and tubs in many jurisdictions.
- Anti-Siphon Valve
- A device preventing backflow of potentially contaminated water into the potable water supply. Required on outdoor hose bibs.
- Auger
- A flexible cable tool used to clear drain clogs. A toilet auger is designed for toilets; a drain auger (snake) clears sink and tub drains.
B
- Backflow
- The reverse flow of water or other substances from a contaminated source into the clean water supply. Prevented by backflow preventers and check valves.
- Backflow Preventer
- A device installed on water lines to prevent contaminated water from flowing backward into the potable supply. Required on irrigation systems and some commercial applications.
- Ball Valve
- A shutoff valve using a rotating ball with a hole through its center. Provides reliable full-open or full-closed operation. Preferred for main shutoffs.
- Ballcock
- The float-controlled valve inside a toilet tank that refills the tank after flushing. Also called a fill valve. Modern ballcocks use a float cup design.
- Baseboard Heater
- An electric or hydronic heating unit installed along the base of walls. Hydronic versions use hot water circulated from a boiler.
- Boiler
- A heating system that heats water and distributes it (or steam) through pipes to radiators or baseboard units. Common in older Columbus homes.
- Branch Line
- A secondary pipe branching off a main supply or drain line to serve individual fixtures.
- BTU (British Thermal Unit)
- A unit of heat energy. Used to rate heating and cooling capacity — one BTU raises one pound of water by one degree Fahrenheit.
- BTUh
- BTU per hour — the standard rating for HVAC equipment capacity.
- Building Trap
- A large P-trap installed in a home’s main drain line where it exits to the sewer. Prevents sewer gases from entering the building.
C
- Capacitor
- An electrical component in HVAC systems that stores energy and provides starting and running power to motors. Failed capacitors are among the most common AC repairs.
- Cast Iron Pipe
- Traditional drain and sewer pipe material used in homes built before the 1970s. Durable but susceptible to internal corrosion over decades of use.
- Cavitation
- The formation and collapse of vapor bubbles in a pump caused by pressure differentials. Creates noise, vibration, and can damage pump components.
- Check Valve
- A valve allowing flow in one direction only. Used to prevent backflow in sump pump discharge lines and other applications.
- Cleanout
- A removable plug in a drain line providing access for clearing blockages. Required at specific intervals in drain systems per code.
- Coefficient of Performance (COP)
- An efficiency ratio for heat pumps — the amount of heating or cooling produced per unit of electrical energy consumed.
- Compression Fitting
- A plumbing connection using a compression ring and nut to seal around a pipe without soldering. Used in shutoff valves and supply lines.
- Condensate Line
- The drain line removing water condensed from humid air as it passes over the AC evaporator coil. Requires periodic flushing to prevent clogs and water damage.
- Condenser
- The outdoor unit of a split AC system containing the compressor, condenser coil, and fan. Releases heat absorbed from inside the building.
- Copper Pipe
- The most common water supply pipe material in homes built from the 1950s–2000s. Durable and resistant to bacteria growth. Susceptible to pinhole leaks in acidic water conditions.
- CPVC (Chlorinated Polyvinyl Chloride)
- A plastic pipe rated for hot water supply lines. Common in newer construction as an alternative to copper.
- Cross Connection
- Any physical connection between the potable water supply and a non-potable source. A code violation requiring immediate correction.
D
- Damper
- An adjustable plate inside ductwork controlling airflow to individual zones or rooms.
- Dielectric Union
- A fitting connecting pipes of different metals (copper and galvanized steel) while preventing galvanic corrosion. Required at water heater connections in many codes.
- Diverter Valve
- A valve redirecting water from a tub spout to a shower head, or between multiple outlets.
- Drain, Waste, and Vent (DWV) System
- The network of drain pipes, waste pipes, and vent pipes that removes waste water and maintains proper pressure in the drain system.
- Drain Snake
- A flexible cable inserted into drains to break up or retrieve clogs. Hand snakes address minor clogs; machine-powered snakes clear main lines.
- Drywall Repair
- Restoration of damaged drywall after plumbing or HVAC access. Responsible plumbing contractors repair access holes as part of the job.
- Dual-Flush Toilet
- A toilet with two flush options — a smaller flush for liquid waste (0.8 gpf) and a full flush for solid waste (1.6 gpf).
- Duct Leakage
- Air escaping from unsealed ductwork joints and connections. Typical homes lose 20–30% of conditioned air through duct leakage, significantly increasing energy costs.
- Ductless System
- An HVAC system delivering conditioned air directly to individual spaces without ductwork. Also called mini-split. Highly efficient and ideal for additions or converted spaces.
E
- Effluent
- Treated wastewater discharged from a septic system into a drain field.
- Elbow
- A plumbing fitting changing pipe direction — typically 45 or 90 degrees.
- Electronic Air Cleaner
- An HVAC filtration component using an electrical charge to attract and capture airborne particles. More effective than standard filters for allergen removal.
- Electrostatic Filter
- A reusable HVAC filter using static electricity to attract particles. Higher filtration efficiency than standard fiberglass filters.
- Energy Recovery Ventilator (ERV)
- A ventilation system that exchanges stale indoor air with fresh outdoor air while transferring heat and moisture to improve efficiency.
- Evaporator Coil
- The indoor HVAC component where refrigerant absorbs heat from indoor air, cooling it. Located in the air handler. A dirty evaporator coil significantly reduces system efficiency.
- Expansion Tank
- A small pressurized tank installed on water heater supply lines in closed plumbing systems to absorb thermal expansion of heated water. Required by code in many installations.
F
- Fill Valve
- The valve controlling water flow into a toilet tank after flushing. Also called a ballcock or float valve. A continuously running toilet often indicates a failed fill valve.
- Flapper
- The rubber seal at the bottom of a toilet tank that opens during flushing and closes to allow refilling. The most common cause of a running toilet.
- Flashing
- Sheet metal or other material sealing gaps where plumbing pipes penetrate roofing. Failed flashing is a common source of roof leaks.
- Flame Sensor
- A furnace safety component detecting whether the burner has ignited. A dirty flame sensor is one of the most common causes of furnace failures. Cleaned during annual maintenance.
- Flapper Valve
- See Flapper. Also refers to similar valve mechanisms in other plumbing applications.
- Float Ball
- The ball-shaped float in older toilet tanks that rises with the water level to shut off the fill valve. Replaced in most modern toilets by float cup designs.
- Floor Drain
- A drain installed in a concrete floor to remove water from flooding, HVAC condensate, or water heater overflow. Should be tested periodically and kept clear.
- Flow Restrictor
- A device limiting water flow from a fixture to reduce water consumption. Used in showerheads and some faucets to meet WaterSense standards.
- Flue
- A pipe or chimney channel venting combustion gases from a furnace, boiler, or water heater to the outside. Blocked or damaged flues create carbon monoxide hazards.
- Flux
- A chemical paste applied to copper pipe joints before soldering (sweating) to clean the metal surface and ensure a reliable solder bond.
- Freeze Protection
- Measures taken to protect plumbing from freezing temperatures — insulation, heat tape, and maintaining minimum indoor temperature above 55°F.
- Frost-Proof Hose Bib
- An outdoor faucet with the valve mechanism set 6–12 inches inside the wall to protect against freezing. The standard for exterior faucets in Ohio.
G
- Galvanized Steel Pipe
- Steel pipe coated with zinc to resist corrosion. Common in homes built before the 1960s. Prone to rust buildup that restricts flow over decades.
- Gas Line
- The piping system delivering natural gas or propane to appliances. Must be installed by licensed technicians following local code.
- Gate Valve
- A shutoff valve using a rising gate to control flow. Less reliable than ball valves for frequent operation but common as older main shutoffs.
- Globe Valve
- A valve using a circular disk to regulate flow. Used where precise flow control is needed rather than simple on/off operation.
- GPH (Gallons Per Hour)
- A flow rate measurement used for water heaters and water treatment systems.
- GPM (Gallons Per Minute)
- The standard measurement of water flow rate at fixtures and in supply systems.
- Greywater
- Wastewater from sinks, showers, and washing machines (not toilets). Can be treated and reused for irrigation in some jurisdictions.
- Ground Fault Circuit Interrupter (GFCI)
- An electrical safety device required near water sources that shuts off power instantly when it detects a ground fault. Required in bathrooms, kitchens, and outdoor receptacles.
H
- Hard Water
- Water containing high concentrations of dissolved calcium and magnesium. Columbus, Ohio has moderately hard water. Hard water causes scale buildup in pipes and appliances.
- Heat Exchanger
- The component in a furnace that separates combustion gases from the air being heated. A cracked heat exchanger allows carbon monoxide to enter living spaces — a serious safety hazard requiring immediate replacement.
- Heat Pump
- An HVAC system transferring heat between indoor and outdoor air rather than generating it. Provides both heating and cooling. Modern cold-climate heat pumps operate efficiently down to -13°F.
- High-Efficiency Furnace
- A furnace with 90%+ AFUE rating. Uses a secondary heat exchanger to extract additional heat from combustion gases. Vents through PVC pipe instead of a flue.
- Hose Bib
- An outdoor water faucet. Also called a sillcock. Ohio homes require frost-proof hose bibs to prevent freeze damage.
- Hot Tap
- A plumbing connection made to a live pressurized pipe without shutting off the water supply.
- Humidifier, Whole-Home
- An HVAC component adding moisture to heated air to maintain comfortable indoor humidity during dry Ohio winters. Reduces static electricity and protects wood furniture and flooring.
- Hydro Jetting
- High-pressure water drain cleaning using streams up to 4,000 PSI to clear grease, scale, and root intrusion. More effective than snaking for persistent blockages.
- Hydronic System
- A heating or cooling system using water as the heat transfer medium. Includes baseboard radiators, radiant floor heating, and chilled beam systems.
I
- Igniter
- The component in a gas furnace that ignites the burner. Hot surface igniters glow to ignite gas; spark igniters create an electrical spark. Failed igniters cause furnaces to run without producing heat.
- Indirect Water Heater
- A water heater that uses heat from a boiler rather than its own burner. Efficient when paired with a modern boiler.
- Inline Filter
- A water filter installed directly in a supply line to treat water at a specific point of use.
- Isolation Valve
- A shutoff valve allowing individual fixtures or systems to be isolated without interrupting water to the rest of the building.
J
- Jetter
- A drain cleaning machine using high-pressure water. See Hydro Jetting.
- J-Trap
- Another name for a P-trap — the curved drain pipe under sinks that holds water to block sewer gases.
- Junction Box
- An electrical enclosure where wires are connected. Required for all electrical connections, including those for HVAC equipment.
K
- Kilowatt (kW)
- A unit of electrical power equal to 1,000 watts. Used to measure the capacity of electric heating elements and HVAC equipment.
- Kilowatt-Hour (kWh)
- A unit of electrical energy equal to 1 kilowatt of power used for 1 hour. The standard billing unit for electricity.
- Kinetic Water Ram
- A tool using compressed air to clear drain clogs. An alternative to snaking for clogs close to the drain opening.
L
- Latent Heat
- Heat energy that changes the phase of a substance (liquid to gas) without changing its temperature. Important in HVAC — air conditioners remove latent heat when dehumidifying air.
- Lead Service Line
- Water supply lines made of lead, common in Columbus homes built before 1986. The City of Columbus has an active program to replace lead service lines.
- Leak Detection
- Professional service using pressure testing, acoustic equipment, and thermal imaging to locate hidden plumbing leaks without unnecessary demolition.
- Low-Flush Toilet
- A toilet using 1.28–1.6 gallons per flush compared to older 3.5–5 gpf models. The modern standard in plumbing codes.
M
- Main Line
- The primary drain pipe carrying waste from all fixtures to the sewer. Main line clogs affect multiple fixtures simultaneously.
- Main Shutoff
- The valve controlling water supply to the entire building. Know its location before a plumbing emergency. Usually located near the water meter or where the supply enters the building.
- Manifold
- A distribution point where a main pipe branches into multiple smaller lines. PEX manifold systems allow individual fixture shutoffs without accessing walls.
- MERV Rating
- Minimum Efficiency Reporting Value — a scale rating HVAC filter efficiency. Higher MERV = smaller particles captured. MERV 8–13 is typical for residential use; higher ratings restrict airflow.
- Mini-Split
- See Ductless System.
- Mixing Valve
- A valve blending hot and cold water to deliver a consistent mixed temperature. Used in anti-scald applications and tankless water heater systems.
- Multi-Zone HVAC
- An HVAC system dividing a building into independently controlled temperature zones. Common in larger Columbus homes with multiple floors or additions.
N
- Natural Gas
- The primary fuel for heating systems and water heaters in Columbus, Ohio. Supplied by Columbia Gas of Ohio. Requires licensed technicians for all connection and repair work.
- Needle Valve
- A precise flow control valve used in low-flow applications. Less common in residential plumbing.
- No-Hub Coupling
- A rubber coupling with stainless steel clamps connecting cast iron or plastic drain pipes without hubs. Commonly used for repairs.
O
- Offset
- A drain pipe configuration using two angled fittings to shift the pipe horizontally while maintaining grade.
- Open Loop System
- A geothermal or heat pump system using groundwater as the heat exchange medium, drawing from and returning to an aquifer.
- Overflow Tube
- The vertical tube in a toilet tank that allows water to flow into the bowl if the fill valve fails to shut off, preventing tank overflow.
P
- P-Trap
- The curved pipe section under sinks, tubs, and showers that holds standing water to block sewer gases from entering. Every drain fixture requires a P-trap.
- Packaged Unit
- An HVAC system containing all components (compressor, coils, air handler) in one outdoor cabinet. Common in commercial applications and some single-story homes.
- PEX Pipe
- Cross-linked polyethylene — a flexible plastic pipe replacing copper in most new residential construction. Resistant to freeze damage and scale buildup. Easier and less expensive to install than copper.
- Pipe Insulation
- Foam or fiberglass wrap applied to pipes in unconditioned spaces to prevent heat loss and freeze damage.
- Plenum
- The chamber distributing conditioned air from the air handler into the duct system.
- Plumbing Code
- The adopted standards governing plumbing installation and repair in a jurisdiction. Ohio uses the Ohio Plumbing Code based on the International Plumbing Code.
- Potable Water
- Water safe for human consumption. The potable water supply must be protected from cross connections with non-potable sources.
- Pressure Balancing Valve
- A shower valve maintaining consistent water temperature when other fixtures change pressure. Prevents scalding when a toilet is flushed during a shower.
- Pressure Reducing Valve (PRV)
- A device reducing water pressure from the municipal supply to safe household levels (typically 60–80 PSI). High water pressure damages fixtures and appliances.
- PVC Pipe
- Polyvinyl chloride — a plastic pipe used for drain, waste, and vent systems. White PVC is used for drain lines; gray Schedule 80 PVC for pressure applications.
R
- Radiant Floor Heating
- A hydronic or electric heating system embedded in floors. Provides even, comfortable heat and eliminates cold floors in Columbus winters.
- Refrigerant
- The fluid circulating in HVAC systems that absorbs and releases heat. R-410A was the standard; R-32 and R-454B are the newer environmentally preferred alternatives.
- Relief Valve
- See Temperature and Pressure Relief (TPR) Valve.
- Reverse Osmosis
- A water filtration process forcing water through a semi-permeable membrane to remove dissolved solids, contaminants, and minerals.
- Rough-In
- The initial plumbing work installed during construction before walls are closed — supply lines, drain pipes, and vent stacks positioned for future fixture connections.
S
- S-Trap
- An older drain trap configuration prone to siphoning. No longer permitted by modern plumbing codes; P-traps are required.
- SEER (Seasonal Energy Efficiency Ratio)
- The efficiency rating for air conditioning systems. Higher SEER = more efficient. Minimum federal standard is SEER 14 in Ohio (2023 update).
- Septic System
- An on-site wastewater treatment system for properties not connected to a municipal sewer. Requires periodic pumping and field line maintenance.
- Service Panel
- The electrical distribution board containing circuit breakers or fuses. HVAC and plumbing equipment are connected to dedicated circuits in the service panel.
- Sewer Gas
- A mixture of gases including hydrogen sulfide, methane, and ammonia produced by decomposing waste in sewer systems. P-traps and vent stacks prevent sewer gas from entering buildings.
- Sewer Line
- The drain pipe from a building to the municipal sewer. Homeowners are responsible for the sewer line from their foundation to the street connection.
- Shut-Off Valve
- Any valve stopping water flow to a fixture or system. Every fixture should have an accessible shutoff valve for emergency isolation.
- Sillcock
- An outdoor faucet. See Hose Bib.
- Slab Leak
- A water or drain pipe leak beneath a concrete foundation. Requires specialized detection and repair — either breaking the slab, tunneling, or rerouting pipes through walls.
- Slope
- The downward angle of horizontal drain pipes to maintain flow by gravity. Standard slope is 1/4 inch per foot of horizontal run.
- Smart Thermostat
- A programmable thermostat connecting to WiFi for remote control and learning occupant patterns to optimize energy use. Popular brands include Nest, Ecobee, and Honeywell Home.
- Soil Stack
- The main vertical drain pipe running from the basement to roof, serving multiple floors of drains and toilets.
- Split System
- The most common HVAC configuration — a separate indoor air handler and outdoor condenser connected by refrigerant lines.
- Sump Pump
- A pump removing water accumulated in a basement sump pit. Critical in Columbus homes during spring rains and flooding. Should be tested annually and have a battery backup.
- Supply Line
- The flexible tube connecting a fixture shutoff valve to the faucet or toilet. Should be replaced every 5–10 years.
- Sweat (Soldering)
- The process of joining copper pipe using a torch, flux, and solder. Requires an open flame and proper training for safe execution.
T
- Tankless Water Heater
- An on-demand water heater heating water as it flows through the unit rather than storing it. Provides endless hot water and uses less energy than tank heaters. Also called an instantaneous or on-demand water heater.
- Temperature and Pressure Relief (TPR) Valve
- A safety valve on water heaters releasing pressure if the tank exceeds safe temperature or pressure limits. Must be tested annually and replaced if it fails to reseat properly.
- Thermostatic Expansion Valve (TXV)
- A precise refrigerant metering device in HVAC systems that improves efficiency by controlling refrigerant flow based on superheat.
- Ton (HVAC)
- A unit of cooling capacity. One ton equals 12,000 BTU/h — the heat absorbed by melting one ton of ice in 24 hours. Residential systems typically range from 1.5 to 5 tons.
- Trap
- A curved pipe section holding water to block sewer gas. Required on every drain fixture. See P-Trap.
- Trenchless Sewer Repair
- Sewer line repair or replacement without excavating the full length of the pipe. Methods include pipe bursting and pipe lining (CIPP). Minimizes landscape disruption.
U
- Ufer Ground
- A grounding electrode using steel reinforcement in a concrete foundation to ground the electrical system.
- Union
- A three-piece fitting allowing pipes to be disconnected without cutting. Used for maintenance access on water heaters, pumps, and other serviceable components.
V
- Vacuum Breaker
- A device preventing backflow by introducing air into a pipe when pressure drops below atmospheric. Required on toilet fill valves and hose bibs.
- Valve
- A device controlling fluid flow in a pipe. Types include ball valves, gate valves, check valves, and pressure reducing valves.
- Variable-Speed Drive (VSD)
- A motor controller varying compressor or fan speed to match load conditions. Improves efficiency and comfort in modern HVAC systems.
- Vent Stack
- A vertical pipe extending from drain lines through the roof to maintain atmospheric pressure in the drain system and vent sewer gases outdoors. Blocked vent stacks cause slow drains and gurgling sounds.
- Venturi
- A flow measurement device using pressure difference at a constriction. Used in gas appliance mixers and some water flow meters.
W
- Water Hammer
- A banging sound in pipes caused by sudden changes in water velocity — often from fast-closing solenoid valves in appliances. Prevented by water hammer arrestors installed at fixtures.
- Water Heater
- An appliance heating water for household use. Types include tank (storage), tankless, heat pump, and solar. Tank water heaters should be replaced after 10–12 years.
- Water Main
- The municipal water supply pipe in the street. The homeowner’s supply connects to the water main at the curb stop.
- Water Pressure
- The force of water in the supply system, measured in PSI. Normal residential pressure is 40–80 PSI. High pressure (over 80 PSI) damages fixtures and appliances.
- Water Softener
- An appliance removing calcium and magnesium from hard water using ion exchange. Reduces scale buildup in pipes, water heaters, and appliances. Recommended for Columbus’s moderately hard water.
- Wet Vent
- A vent pipe also carrying drain water from a fixture above. Permitted under specific conditions by most plumbing codes.
- Wye (Y-Fitting)
- A pipe fitting with three openings at a Y-shaped angle. Used for drain line connections and cleanout installations.
Z
- Zone Valve
- A valve controlling hot water flow to a specific zone in a hydronic heating system. Allows independent temperature control in different areas.
- Zoning
- Dividing an HVAC system into independently controlled areas. Improves comfort and efficiency by conditioning only occupied spaces.
Additional Resources
For plumbing or HVAC questions not covered here, visit our FAQ page or call Transit & Flow at (614) 333-8092. Our licensed technicians serve Columbus, Dublin, Westerville, Hilliard, Grove City, Gahanna, New Albany, Upper Arlington, Powell, Short North, and all surrounding communities.
See also: Plumbing Services | Heating Services | Air Conditioning Services | Service Areas