Pool Service Terminology Glossary

Pool service professionals and property owners encounter a dense layer of technical vocabulary spanning water chemistry, mechanical systems, regulatory compliance, and service delivery logistics. This glossary defines the core terms used across residential and commercial pool maintenance contexts in the United States. Precise language matters when evaluating pool service contracts and agreements, interpreting inspection reports, or comparing types of pool services explained across providers. Entries are organized by functional category to support practical cross-referencing.

Definition and scope

A pool service terminology glossary serves as a standardized reference for the vocabulary used by licensed technicians, inspectors, health department officials, and pool owners across the pool and spa industry. The scope covers water chemistry parameters, mechanical components, service protocols, regulatory designations, and contractual terms.

The Pool & Hot Tub Alliance (PHTA), formerly known as the Association of Pool & Spa Professionals (APSP), maintains industry-recognized standards including ANSI/PHTA/ICC-1 (residential pools) and ANSI/PHTA-7 (public pools and spas), which define many terms used in professional practice (PHTA Standards). The Model Aquatic Health Code (MAHC), published by the Centers for Disease Control and Prevention (CDC), provides a parallel definitional framework for public aquatic venues (CDC MAHC).

How it works

Terminology in pool service operates across four distinct functional layers:

Water chemistry terms — Parameters governing biological safety and equipment protection, including pH, total alkalinity (TA), calcium hardness (CH), cyanuric acid (CYA), and oxidation-reduction potential (ORP).
Mechanical and equipment terms — Vocabulary describing pump types, filter media, heater configurations, and automated control systems.
Service and protocol terms — Language used in service agreements, technician reports, and inspection checklists.
Regulatory and compliance terms — Designations drawn from state health codes, local ordinances, and national model codes.

Core water chemistry definitions:

pH — A logarithmic scale measuring hydrogen ion concentration in pool water. The CDC MAHC specifies an acceptable operating range of 7.2 to 7.8 for public pools (CDC MAHC, Section 6).
Free Available Chlorine (FAC) — The portion of total chlorine that remains active as a disinfectant. MAHC requires a minimum FAC of 1 ppm in non-cyanuric-acid-stabilized pools.
Combined Chlorine (CC) — Chlorine that has bonded with ammonia or nitrogen compounds, forming chloramines. High CC levels (above 0.4 ppm) are associated with eye and respiratory irritation and trigger pool shock treatment services.
Cyanuric Acid (CYA) — A chlorine stabilizer that reduces UV degradation of FAC. MAHC caps CYA at 90 ppm for pools using it. Excess CYA reduces disinfection efficacy through chlorine lock.
Total Dissolved Solids (TDS) — The cumulative concentration of all substances dissolved in pool water, measured in parts per million (ppm). Elevated TDS — typically above 1,500 ppm over the source water baseline — degrades water clarity and chemical efficiency, often necessitating pool drain and refill services.
Saturation Index (Langelier Saturation Index / LSI) — A calculated value combining pH, alkalinity, calcium hardness, temperature, and TDS to predict whether water will be scale-forming (+), corrosive (−), or balanced (0). A target LSI of −0.3 to +0.3 is the standard operational range.
Oxidation-Reduction Potential (ORP) — Measured in millivolts (mV), ORP indicates the oxidizing capacity of pool water. An ORP of 650–750 mV is generally associated with effective disinfection per PHTA guidance.

Mechanical and equipment definitions:

Variable-Speed Pump (VSP) — A pump with an electronically commutated motor (ECM) that operates across multiple speed settings. The U.S. Department of Energy's pool pump efficiency rule under 10 CFR Part 431 mandates VSP technology for most new residential pool pump installations (DOE 10 CFR Part 431).
Diatomaceous Earth (DE) Filter — A filtration system using fossilized diatom skeletons as filter media, capable of filtering particles down to 2–5 microns. Compared to sand filters (20–40 microns) and cartridge filters (10–15 microns), DE systems offer the finest filtration grade. See pool filter cleaning and servicing for maintenance protocol context.
Backwash — The process of reversing water flow through a sand or DE filter to flush accumulated debris to waste. Backwashing reduces filter media effectiveness over time and triggers periodic media replacement.
Turnover Rate — The time (in hours) required for the pump and filtration system to circulate the entire pool volume once. MAHC Section 5 recommends a maximum 6-hour turnover for most public pools.

Common scenarios

Scenario 1 — Chlorine demand: A technician documents "chlorine demand" when pool water consumes added chlorine without producing measurable FAC. This occurs after algae blooms or heavy bather loads and necessitates pool algae treatment services before normal chemistry can be restored.

Scenario 2 — Salt system terminology: In pool service for saltwater pools, terms such as salt cell, chlorine generator, and electrolytic chlorination describe a system converting sodium chloride (NaCl) dissolved at 2,700–3,400 ppm into hypochlorous acid via electrolysis. The salt cell generates FAC continuously, replacing the need for direct chlorine addition.

Scenario 3 — Inspection and permitting language: Commercial operators encounter terms such as operator of record, variance, inspection cycle, and closure order from state health departments administering public pool regulations. Residential contractors use terms like barrier compliance, entrapment protection, and SVRS (Safety Vacuum Release System) in reference to Virginia Graeme Baker Pool and Spa Safety Act requirements (VGB Act, 15 U.S.C. §8001 et seq.).

Decision boundaries

Distinguishing between closely related terms prevents misdiagnosis of water or equipment problems:

Cloudy water vs. green water — Cloudy water indicates elevated TDS, high alkalinity, or filtration failure; green water indicates active algae growth requiring targeted biocide treatment, not simply increased filtration.
Shocking vs. superchlorination — Shocking raises FAC to 10× the CC level to break chloramine bonds (breakpoint chlorination). Superchlorination raises FAC to 10 ppm or above for general oxidation without necessarily reaching breakpoint.
Stabilized vs. unstabilized chlorine — Trichlor and dichlor contain CYA; calcium hypochlorite and sodium hypochlorite do not. Exclusive use of stabilized chlorine in outdoor pools causes progressive CYA accumulation.
Service agreement vs. maintenance contract — A service agreement typically defines discrete visit tasks; a maintenance contract may include parts, chemical costs, and equipment warranties as bundled obligations. The distinction affects liability scope and is addressed further at pool service industry standards.

For context on how these terms apply across service delivery frequency and scope, the pool service frequency guide provides operational detail. Technician qualification terminology — including CPO (Certified Pool Operator), AFO (Aquatic Facility Operator), and state-specific license designations — is covered at pool service technician qualifications.

References

📜 5 regulatory citations referenced · 🔍 Monitored by ANA Regulatory Watch · View update log