Pool Equipment Glossary: Pumps, Filters, Heaters & Water Care
A practical A–Z reference to pool hardware, plumbing, filtration, heating, sanitation and the terms on equipment labels.
Pool manuals and service estimates use terms that sound interchangeable but describe different jobs. A pump moves water; a filter captures particles; a heater adds heat; a sanitizer helps control microbes. This glossary explains what each component does, where it fits, and what to check before choosing a replacement.
How the pool circulation system fits together
Most conventional pools pull water through one or more suction points, push it through a pump and filter, and return it to the pool. Heaters, salt chlorine generators, and other treatment devices may be installed in the return plumbing, subject to manufacturer requirements. Not every pool has every component, and the actual plumbing sequence can vary.
Five terms that explain the equipment pad
Conceptual flow only, not a construction diagram. Actual heater and sanitizer placement, check valves, and required straight pipe lengths depend on equipment instructions.
Movement is not cleaning
The pump creates flow; the filter removes particles. Neither automatically guarantees adequate sanitizer.
Flow is not pressure
Flow describes water volume per time; pressure describes resistance at a measurement point.
Sanitizer is not filtration
Chlorine helps control microorganisms; filtration physically removes suspended material.
Pumps and plumbing: the terms owners see most
| Term | Meaning | Why it matters |
|---|---|---|
| Circulation pump | Motor-driven device that moves water through the pool system | Must be compatible with plumbing, filter and other equipment |
| Variable-speed pump (VSP) | Pump whose motor speed can be adjusted | Flow and energy use vary with speed and system resistance |
| Priming | Removing enough air from the pump's wet end so it can move water | Running dry can damage the pump |
| Strainer basket | Removable basket ahead of the pump impeller | Captures larger debris before it reaches the impeller |
| Impeller | Rotating pump component that imparts energy to water | Blockage or damage can reduce flow |
| Check valve | Valve designed to resist reverse flow | Placement and material must suit the system |
| Union | Detachable plumbing connection | Allows service without cutting the pipe |
| GPM | Gallons per minute, a measure of flow rate | Used to evaluate equipment operating requirements |
| Head | Energy required to overcome elevation and system resistance, often expressed in feet | Pump performance depends on total dynamic head |
Filters and cleaning: terms that are often confused
| Term | Definition | Practical distinction |
|---|---|---|
| Cartridge filter | Filter using pleated replaceable or washable elements | Typically cleaned by removing and rinsing elements per manual |
| Sand filter | Filter using a specified granular medium | Some models use backwashing to remove collected debris |
| DE filter | Filter using diatomaceous-earth media on internal grids or elements | Requires model-specific handling and media replenishment |
| Backwash | Reversing flow through a compatible filter to discharge captured dirt | Not a universal cleaning method for cartridge filters |
| Clean-filter pressure | Gauge reading after the filter is clean at a known pump setting | Useful baseline for determining when service is needed |
| Micron | One millionth of a meter | Used to describe particle size; claims vary by test conditions |
| Skimmer | Surface-water inlet that collects floating debris | Not the same as a filter or pump strainer |
Heating and automation vocabulary
A heat pump transfers heat from surrounding air to pool water; a gas heater produces heat by burning fuel. BTU/h describes heating rate, while COP compares heat output with electrical energy input under stated conditions. A solar pool cover reduces evaporation and associated heat loss; it is not a substitute for a compliant safety cover. Automation controller refers to equipment that schedules or coordinates devices; a relay switches a circuit, and a temperature sensor provides a reading to a controller. Compatibility depends on the actual models and control protocols.
Water chemistry and sanitation: what each measurement tells you
| Term | Plain-English meaning | What it does not mean |
|---|---|---|
| Free chlorine (FC) | Chlorine available for disinfection | Not the same as total chlorine |
| Combined chlorine (CC) | Chlorine bound in certain reaction products | Not a direct count of germs |
| pH | Measure of acidity or basicity | Not the same as alkalinity |
| Total alkalinity (TA) | Water's capacity to resist pH change | Not a sanitizer measurement |
| Cyanuric acid (CYA) | Stabilizer that slows sunlight-related chlorine loss | Not chlorine itself |
| Calcium hardness | Concentration of dissolved calcium, expressed as a hardness measure | Not the same as total alkalinity |
| Salt chlorine generator (SWG) | Device that uses dissolved salt and electricity to generate chlorine | Not a chlorine-free pool system |
| UV system | Device exposing circulating water to ultraviolet light | Does not provide lasting sanitizer residual in the pool |
| Ozone system | Device introducing ozone for supplemental treatment | Does not replace the need for an approved residual sanitizer |
Equipment labels: five numbers worth recording
Record the manufacturer and model, electrical rating, pipe connection size, filter type or element number, and any minimum or maximum flow requirement stated by the manufacturer. Photograph the full label before ordering replacement parts. Similar-looking housings can contain different seals, motors, or control boards. Use the serial number when the manufacturer requests it, but do not publish it in public troubleshooting forums.
When to use a deeper guide instead of a glossary
A glossary helps identify the part and interpret terminology. It cannot diagnose a failed pump, establish safe electrical wiring, calculate a specific heater size, or determine chemical doses without measurements. For those jobs, follow the equipment-specific guides linked below, the product manual, and qualified service where required. Treat any claimed universal filter-pressure threshold, pump run time or chlorine dose with caution: conditions and products differ.
Useful reference tools for pool owners
Measure the sanitizer and balance parameters relevant to your pool rather than guessing from appearance.
Compare water test kits →Match thread size, measurement range and installation requirements to the filter model.
Compare filter gauges →Affiliate disclosure: As an Amazon Associate, we may earn from qualifying purchases. Check compatibility and current pricing before purchasing.
Frequently asked questions
What is the difference between a pool pump and a pool filter?
A pump circulates water; a filter captures suspended particles. Both contribute to water care but do different jobs.
Is a skimmer the same thing as a pump basket?
No. A skimmer collects debris at the water surface, while the strainer basket inside the pump housing catches debris before the impeller.
What does GPM mean on pool equipment?
GPM means gallons per minute, a measure of flow. Actual flow depends on pump speed and plumbing resistance.
What is the difference between filter pressure and water flow?
Pressure reflects conditions at the gauge location; flow is the volume moving per minute. One cannot be reliably inferred from the other without system information.
Does a saltwater pool still use chlorine?
Yes. A salt chlorine generator produces chlorine from dissolved salt; it does not eliminate the need for sanitizer testing.
What is the difference between free chlorine and combined chlorine?
Free chlorine is available for disinfection; combined chlorine refers to certain chlorine reaction products. Testing methods and interpretation matter.
Is a solar cover the same as a pool safety cover?
No. A solar cover primarily reduces evaporation and heat loss. It should never be assumed to meet safety-cover requirements.
What information do I need before ordering a pool replacement part?
Record the exact manufacturer and model, part number where available, connection dimensions, and electrical or flow specifications relevant to the component.