9102 Sweetbrush Dr, Houston, TX 77064
Working Time: 24 Hour Service - 7 Days a Week

Pool Terminology

GLOSSARY OF SOME OF THE TERMS USED IN THE SWIMMING POOL TERMINOLOGY USED IN THE CONSTRUCTION INDUSTRY

  1. Acid is a sour chemical substance that contains hydrogen, and it can dissolve metals, neutralize acid materials and combine bases to make salts. The acid reduces the pH and total alkalinity in a swimming pool or spa water. Two examples are muriatic acid (hydrochloric) and dry acid (sodium bisulfate).
  2. Acid Demand: The amount required to bring the pH and total alkalinity to their correct levels. The acid demand test determines this.
  3. Acid Demand test: This reagent test is used in conjunction with a pH test to determine how much acid is needed to lower pH levels and total alkalinity.
  4. Acid rain: Precipitation with an unusually low pH value (4.5- or lower) due to absorption of carbon dioxide, sulfur dioxide, and nitrous oxide.
  5. Acrylic – A thermoplastic sheet that is molded into a mold for making a spa or other related equipment. The sheet is heated first, then vacuumed onto a mold.
  6. Air Blower – A device that blows air through holes in the floor or bubbler ring or hydrotherapy jets at a spa.
  7. Air-Relief Valve: A manually-operated brass or plastic valve that is located at the top end of a filter tank. It relieves pressure and allows air to escape the filter. This is also called bleeding the filter. Sometimes called a pressure relief valve.
  8. Algae – Microscopic plants-like organisms that have chlorophyll. Algae use sunlight for photosynthesis and are nourished with carbon dioxide (CO2). It can be introduced from rain or wind, and it grows in colonies that produce nuisance masses. Although it does not cause disease, algae can harbor bacteria and is slippery. There are over 21,000 species of algae. The most popular pool types are black, blue-green, and green. Although pink or red-colored algae-like organisms are possible, they are not algae. It is possible to prevent it from happening by using the right sanitizer levels and shocking or super chlorination.
  9. Algaecide – Also known as an algicide, a natural or synthetic chemical that kills, destroys or controls algae.
  10. Alkali – Also known as base, a group of compounds that react with acids to make salt. Acid is the opposite of alkali.
  11. Alkalinity – Also known as total alkalinity. The pH-buffering ability of water. Also known as the water’s resistance against pH changes. It is composed of hydroxides, carbonates, and bicarbonates. This is one of the most basic water tests to establish water balance.
  12. Alum – Any of a variety of aluminum compounds that are used in pools to make a gelatinous floc with sand filters, or to coagulate or precipitate suspended particles in water.
  13. Ammonia is introduced into water by swimmers either as waste (perspiration or urine), or through other means. Chloramines, a less effective and disabled form of chlorine, quickly forms in the body. Chloramines and combined chlorine are available.
  14. Anti-Foam: Chemical added to water to remove foam or suds. These products don’t remove the cause of Suding. Most commonly, the water needs to be drained and refilled to get rid of soaps, oils, and other causes that cause foaming. Foaming can be prevented by shock and super chlorination.
  15. Ascorbic acid: A chemical that removes iron stains from fiberglass or vinyl-liner pool.
  16. Automatic Cleaning – A robot that moves through the pool collecting debris. There are also a number of pop-up heads that spray water to cause debris to move towards the bottom drain.
  17. Automatic cover: A system that covers a pool or spa with an electric cover. These systems require that the swimming pool be rectangular in shape. The fence code may not apply if the cover is too tight around the pool, spa, or any other water body that is more than 24 inches in depth. While the cover is primarily used to protect, it also provides significant solar heating and cleaning benefits.
  18. Automatic Pool CLNR – A pool maintenance system that will automatically agitate and vacuum the interior.
  19. Available Content: An index or term that allows you to compare the oxidizing powers of chorine-containing products with gas chlorine. It allows for easy comparison of different chlorine compounds.
  20. Available chlorine: This is the amount of chlorine that is free or combined with the pool water to disinfect it. They are sometimes called residual chlorine.
  21. Backflow: Water backing up through a pipe in a direction that is opposite to normal flow.
  22. Backwash – This is cleaning the filter thoroughly by turning off the water flow.
  23. Bacteria Single-celled microorganisms in a variety of forms. Some of these are potentially harmful or can cause disease. Bromine, chlorine, and other disinfecting agents can control bacteria.
  24. Bactericide – A chemical or element which kills, destroys, or controls bacteria.
  25. Baking soda: Also known as sodium bicarbonate. It is a white powder that raises the alkalinity of spa or pool water without affecting ph.
  26. Balanced water: A water balanced in mineral content and pH to prevent scale formation or corrosion.
  27. Ball Valve is a simple, non-returnable valve consisting of a ball sitting on a cylindrical base within a liquid passageway.
  28. Basis: Also known as primary, this is a group of compounds that react with an acid to make salt. The base is the opposite of an acid. Refer to alkali.
  29. Bleach is a term that refers to liquid chlorine (sodium hypochlorite, 12% available chlorine). This chemical is also used in laundry bleach. However, pool chlorine has 12% available chlorine, and laundry bleach has 5 to 6%%.
  30. The blower is an air pump that pushes air into a spa via the jets or through the holes in the seat.
  31. Blue Fingernails – A condition that is caused by too much copper in the pool water. Chlorine is not responsible for blue fingernails. The bad practice of putting trichlor tabs into the skimmer can lead to copper in the water. This acidic product can cause low-pH water, which will then dissolve metals in equipment. The dissolved metal, usually copper, then stained hair, nails, and eventually pool walls. You can also cause it by using acid or keeping the pH too low.
  32. Chlorination is the process of adding enough free chlorine to completely oxidize any organic matter or other nitrogen compounds. All chlorine added after this point is free of chlorine.
  33. Bromamines are by-products of bromine’s reaction with swimmer waste (perspiration or urine), nitrogen, or fertilizer. Although they don’t smell, bromamines can be active disinfectants that do not cause skin irritations. Super chlorination and shock treatment can remove bromamines.
  34. Bromide is a common name for bromide sodium used to supply bromide ions to water. They can be oxidized or converted into hypobromous acids, which is the poisoning form of bromine. It is used as a disinfectant.
  35. Brominator A mechanical or electric device that dispenses bromine at controlled rates. Bromine tablets are usually stored in a canister, floater, or container.
  36. Bromine is a common name for a chemical composition containing bromine. It’s used to kill bacteria and algae in spas and swimming pools. It is available as a tablet, as well as sodium bromide as a granular form.
  37. BTU is an abbreviation of the British Thermal Unit. Amount of heat required to raise 1 lb. of water 1 degree Fahrenheit.
  38. Buffer is a substance or compound that stabilizes the pH value in a solution. It also refers to water’s resistance to pH changes.
  39. Bypass – A system of pipes, valves, and gates that allows water to flow around an equipment piece or diverted to another piece; it is called a controlled diversion.
  40. Calcium Hypochlorite is a compound of calcium and chlorine that can be used to disinfect, sanitize, and treat spa and swimming pool water. It can be purchased as a white powder or as a tablet for regular and super-chlorination. It typically contains 65% of the available chlorine.
  41. Calcium carbonate Crystalline compounds are formed when pool or spa water levels exceeds the pH, calcium, and total alkalinity. Once crystals are formed, they stick to plumbing, equipment, and the bottom. These crystals are also known as scale.
  42. Calcium chloride: This soluble white salt is used to increase the calcium level or total hardness in a spa or pool.
  43. Calcium Hardness – The water’s calcium content. Sometimes calcium hardness can be confused with total hardness or water hardness. Too much calcium hardness can make the water corrosive. Too much calcium hardness can cause scale formation. Water balance is determined by one of the most basic water tests. 150 ppm is the minimum level. The ideal range is between 200 and 400 ppm.
  44. Cancellation Notice: If a contract was signed at the buyer’s home, a consumer has three days to cancel it.
  45. Cartridge – A porous element made from paper or polyester that can be used to replace the cartridge filter media.
  46. Cartridge filter: A pool water filter or spa that uses a porous element made from paper or polyester.
  47. Cascade – A water feature that flows out of a wall with a raised spa or bond beam.
  48. Centrifugal pump: This is a pump that has an impeller mounted on a rotating shaft. It is enclosed in a casing or volute. The inlet and discharge connections are also included. The centrifugal force and rotation of the impeller create pressure in water.
  49. Check Valve – A device that allows water or air to flow in one direction in a pipe.
  50. Chelate (pronounced KEY-late), also known as the sequester, is the process of preventing water-borne metals from reacting with other water components to create colored precipitates. These precipitates can stain pool walls or produce colored water.
  51. Chelated copper: These are copper algaecides that have a special ingredient to stop the copper from staining the pool bottom or creating colored water.
  52. Chemical Feeder – Any one of several devices that disperse chemicals at a set rate into the spa or pool water. Some dispense chlorine or bromine, while others adjust pH.
  53. A chlorine neutralizer is a chemical that makes chlorine harmless. It is used in pool water testing kits to reduce the bleaching effects of chlorine and bromine. It is also known as a chlorine and bromine neutralizer. The high levels of bromine or chlorine will not cause any harm to swimmers.
  54. Chloramines: Undesirable, foul-smelling, and irritating compounds that form when insufficient amounts of chlorine react with ammonia or other nitrogen-containing substances (swimmer waste, fertilizer and urine, perspiration, and so on). Although chloramines can still be used as disinfectants, they are ineffective and weaker forms of chlorine. Super chlorination and shock treatment can remove chloramines.
  55. Chlorinator – A device that uses a mechanical or electric mechanism to dispense chlorine at a controlled rate. A canister, floater, or container containing tablets of chlorine.
  56. Chlorine is a term that describes any kind of chlorine compound that is used in spa and swimming pool water disinfection or to kill, destroy and control bacteria and algae. Additionally, chlorine can also oxidize ammonia or nitrogen compounds (swimmer waste and bather waste).
  57. Chlorine Need: The amount required to oxidize organic matter (bacteria/algae, chloramines, and ammonia) in the spa or pool water.
  58. Chlorine Enhancer is a chemical compound that, when combined with chlorine, makes chlorine more effective as an algicide.
  59. A chlorine generator is an electrical device that produces chlorine from a salt solution in the tank or salt added to the pool water.
  60. Chlorine Lock – This term implies that a high level of cyanuric acid, a stabilizer or conditioner in water, would cause chlorine to become “locked up”. This is false.
  61. Chlorine Residual – The remaining chlorine in the spa or pool water after satisfying the chlorine demand.
  62. Clarifier – Also known as coagulant or flocculant, a chemical compound that is used to gather (coagulate/agglomerate) or precipitate suspended particles for vacuuming or filtering. There are two types: inorganic aluminum salts (alum) and water-soluble organic polyelectrolytes.
  63. Clarity – The level of transparency in the water.
  64. Coagulant – An organic polyelectrolyte that is used to collect (coagulate), suspended particles in water.
  65. Combined chlorine: Undesirable, foul-smelling, and irritating compounds are formed when insufficient amounts of chlorine react with ammonia or other nitrogen-containing substances (swimmer waste, sweat, and fertilizer, urine, etc.). Although combined chlorine is still effective as a disinfectant, it is weaker and less efficient than the other forms of chlorine.
  66. Conditional License Release: Document signed by a subcontractor, supplier, or contractor certifying that the job was completed in full.
  67. Conditioner Chemically, conditioner refers to cyanuric acid. It slows down the degrading of chlorine in water by sunlight. The minimum level is 10ppm. Too much will not reduce chlorine activity. Bromine is not protected from the sun by conditioner.
  68. Contractor’s Bond: Required by most states. A swimming pool contractor must post a bond to the Contractors Board in Texas. This fund is used to settle any disputes the contractor cannot resolve. You can either post a bond via insurance or cash. A cash bond is generally sounder than one that is posted via insurance.
  69. Contractor’s License: To operate as a swimming pool contractor in Texas, like most other states, you must have a valid contractor’s license, and Texas requires a license. Without a permit, a contractor cannot build a pool, and landscape contractors are also included in this.
  70. Coping – The final edge of the swimming pool. The finished edge of the swimming pool is usually 12 inches in width.
  71. Copper is one of the elements found in nature. Copper is used in plumbing and equipment for swimming pools and spas. Copper can be dissolved from equipment and plumbing by using chemicals that are not needed, improper water balance, or placing trichlor tablets into the skimmer. This can lead to copper forming precipitates on hair, fingernails, and pool walls. Green water can also be caused by high levels of copper. Copper can also be used as an algicide. The maximum level of copper is approximately 0.2 ppm.
  72. Copper Algaecide is a chemical compound that contains copper. Copper sulfate is one of the earliest copper algaecides. Too much copper can cause green-colored stains. Copper algaecides with a newer ingredient are known to prevent copper staining but not inhibit copper’s ability to kill algae. These copper algaecides are known as chelated copper algaecides.
  73. Corrosion: A condition that causes the pool, spa, or equipment to etch, pit, or eat away. This can be caused by a poor water balance, misuse of acidic products, or soft water.
  74. Combining: A fitting is used to join two pipes.
  75. Cover, Hard Top: This is a cover that covers pools, spas, and hot tubs. It rests on the lip of the spa deck or pool deck. It is used to protect swimmers and bathers and also for maintenance and thermal protection.
  76. Cover, Solar – A cover that is placed on the surface of a hot tub, spa, or pool to increase the temperature; it reduces evaporation and prevents wine-borne particles from entering the water.
  77. Winter: Cover that covers the perimeter of a hot tub, spa, or pool. It protects swimmers and debris from the hot tub’s closing time.
  78. Cyanuric Acid – Also known as a condition or stabilizer, cyanuric acid is chemically called a conditioner. It prevents the chlorine in the water from being damaged by sunlight. The minimum level is 10ppm. Too much chlorine does not reduce the effectiveness of the activity of the chlorine, and bromine is not protected from the sun.
  79. D.E. – Diatomaceous Earth is a powder filtering agent that’s made of small sea diatoms. It attaches to the grids of a D.E. It filters out very small particles.
  80. D. E. Filter. Diatomaceous Earth filter – This filter is designed to use diatomaceous (D.E.). The filter medium is diatomaceous earth (D.E.)—the D.E. The D.E. is added to the skimmer by turning on the pump. It is then placed on a grid—the D.E. The D.E then creates the filter medium.
  81. Decking Unless otherwise specified, decking in the swimming pool industry is assumed to be made of concrete. Brick decking or wood decking are examples.
  82. Decks are areas that are directly adjacent to a hot tub, pool, or spa and designed for bathers who want to sit, stand, or walk.
  83. Defoamer is also known as anti-foam. It’s a chemical that is added to water to dissolve the foam or suds. These products don’t remove the cause of sudsing. Most commonly, the water needs to be drained and refilled to get rid of soaps, oils, and other causes that cause foaming. Foaming can be prevented by shock and super chlorination.
  84. Diatomaceous earth: Also known as D.E. A white powder made of fossilized skeletons from one-celled organisms called Diatoms. The skeletons have microscopic gaps and are porous. The powder is added to the skimmer by turning on the pump, and it then deposits itself onto a grid. The powder is then used as the filter medium.
  85. Dichlor It is a fast-dissolving chlorine compound containing cyanuric acid (stabilizer/conditioner). It is neutral in pH and quick-dissolving so that it can be used for super or regular chlorination.
  86. Diffuser: A porous tube, plate, or device that allows air to be forced through and then divided into small bubbles for diffusion in water. An over the drain on Sand filter can be used as a diffuser. A diffuser can also be used to concentrate water flow towards the center of an impeller with closed faces.
  87. Disinfect: To kill pathogenic (disease-causing) organisms.
  88. TDS (Total dissolved solids): This is also known as TDS (Total dissolved solids). It measures the amount of dissolved material in water, and calcium, magnesium, bicarbonates, and sodium are all examples. The high levels can lead to corrosion, color change in water, and salty taste. For pools, the maximum level is 2500ppm. Top-level for spas: 1500 ppm above the starting level.
  89. Diverter Valve: A fitting that changes the direction of the water flow. Diverter valves can be used to switch back the flow to the pool or spa. An Ortega valve, a brand-name diverter valve, is often used to refer to a diverter or valve.
  90. Diving Board – A recreational device for entering a pool. It consists of a semi-rigid, rigid board with a spring attached to the deck and mounted beneath the board.
  91. DPD is an indicator reagent that can be used to determine the presence of total and free chlorine, bromine, and other oxidizers. It is better than OTO for chlorine, as it measures chlorine-free.
  92. Drain – This term refers to the plumbing fitting that is installed at the suction end of a pump for hot tubs, spas, and pools. It is sometimes called the main drain, and it is found in the deepest part of the spa, hot tub, or pool. It is not a drain like a kitchen sink drain. Main drains don’t allow for waste to be drained but instead connect to the pump to circulate and filter.
  93. Dry Acid – Chemically, sodium bisulfate. The addition of water to a dry white crystal will produce acid, and it can be used to lower pH and total alkalinity. It is safer to use than muriatic acid.
  94. Electric Panel – The electricity service for a swimming pool and spa must be provided by the property’s main electrical panel or a subpanel. Sometimes, especially in older homes, an electric panel or service may not be sufficient to handle the pool’s load. A new panel or service might be necessary in this case. This work may incur an additional charge. Ask questions and be careful.
  95. Excavation: The removal of soil to create the swimming pool’s depth. Clients shouldn’t assume that all excavation is included in the project by using this term. There are many pitfalls in misinterpreting what is and isn’t included in a construction contract.
  96. Filter – Apparatus for cleaning the spa or swimming pool water through a tank with cleanable cartridges and grids coated in diatomaceous earth.
  97. Fountain – A water feature with various forms, but often with a man-made appearance.
  98. Freestanding Swimming pool walls are designed and built to stand alone without support from the soil, and this is an example of the condition.
  99. Gas Line – To run a propane or natural gas swimming pool, or heater, the gas must be supplied from either the propane tank or natural gas meter. Gas stubs along the walls of the house will generally not allow for enough flow to operate a gas spa heater or swimming pool. A few exceptions might be made for new construction, where the gas line that runs through the house has the proper size to support a spa heater or swimming pool.
  100. Grading Unless otherwise agreed upon, grading items that are not part of a pool or spa construction contract are not included. Decking is a good example. The grading of the decking must be included in the contract for a swimming pool construction agreement. Extra dirt may need to be hauled away. It is good for the decking contractor to be present on the site during excavation to offer advice.
  101. Gunite – The application of dry cement and sand under pressure at the nozzle.
  102. Hard Ground and Rock: If hard ground or rock is encountered during excavation or trenching for swimming pools and spas, and it is not possible to remove, or within a reasonable timeframe, the tractor will be on-site, and a larger machine, blasting, or other equipment may be required. This is the industry standard.
  103. Heater: A natural gas or electric device that heats water as it passes by it. There is no tank in a spa or swimming pool heater.
  104. HOA approval – Before constructing a pool, approval from the homeowners association may be required. Although they can vary, most HOAs only require the swimming pool design to be approved. It can take up to 30 days, so submitting your application for HOA approval is important as soon as possible. A fee may be charged, and the swimming pool contractor is not responsible for the price.
  105. Drainage: The cost of repairing or rerouting and replacing damaged irrigation or drainage pipes during excavation or trenching for a pool or spa yard is usually the responsibility of their owner. Ask questions and be careful.
  106. Inspection Throughout the construction of your swimming pool, your contractor will request an inspection by the city. The inspector will inspect the project within 24 to 48 hours of receiving your request. The inspector will use the same access points as workers to enter the property. This may cause the homeowner to not know that an inspection was completed. The inspector might leave if the gate is locked or there are dogs. In these cases, a fee may be charged for a re-inspection. The contractor generally pays Re-inspection fees. It is up to the owner to provide access as necessary.
  107. Ledger Stone: Stone-facing walls with a raised bond beam or on the edge of a pool or spa. This type of facing requires more labor and materials than standard facing. Ask questions and be careful.
  108. Main Drain – This is not a drain but a suction point that is connected to the skimmer. Main drains must be split into at least two suction points at least 36 inches apart. Note: Water features, water fountains, etc., may require suction, and you must also split the points to at least 36 inches apart.
  109. Mastic is a flexible compound that is placed between concrete decking and the spa coping. It prevents water from entering the swimming pool decking and causing structural problems like rising or settling.
  110. Mechanical Lien. If a subcontractor, supplier, or person who delivers to or supplies services to your property fails to pay, he can place a lien upon the property to secure his right to payment. Even if a contractor receives compensation, he must still pay his subcontractors or suppliers.
  111. These suppliers and subcontractors retain lien rights. To maintain his lien rights, a subcontractor or supplier must file a preliminary notice within twenty days of completing his work.
  112. “O” Edge: The water feature creates the illusion that the swimming pool is flowing towards the horizon.
  113. Pebble Finish – An upgrade for the bottom of a pool, available in various colors and textures.
  114. Permits – Most cities and counties require a plan review by their zoning and engineering departments before a swimming pool can be built or any other structure. The contractor usually pays the fee for this approval and check. During the construction process, cities and counties may require inspection and acceptance of the work.
  115. Plaster – This is the standard finish for the sides and bottom of a pool, and it can be installed in gray or tan but not in black.
  116. RimFlow: A pool with water at the same level as the surrounding hardscape. This illusion is achieved by running the water through a full perimeter gutter like a “0” edge pool.
  117. Swimming Pool Design Top view of backyard including swimming pool, drawn to scale. Computer software can create 3-D views or perspectives for contractors.
  118. Swimming Pool Engineering: Calculations and structural design of swimming pool according to plan. Each page of engineering and calculation pages must be signed by an engineer certified in most cities. This work is usually done by an outside engineer hired by most swimming pool contractors.
  119. Swimming Pool Equipment – Usually, the pump(s), filter, and heater (if ordered). The swimming pool equipment is usually located between 20 and 50 feet from the spa’s pool. It typically occupies a 3 by the 7-foot rectangle and is approximately 4 feet tall, and it may have a setback from the property lines or openable windows.
  120. Swimming Pool Lighting – Standard pool lighting is 500-watt incandescent. Upgrade lights can be LED or in different colors.
  121. Swimming pool plumbing: PVC (schedules 40 and 80 plastic) is used to place piping that connects with the spa, swimming pool, and water feature circulation elements. There are many types of plumbing available for swimming pools. There are very few building codes related to a spa or swimming pool plumbing. There are no city or county inspections required. Ask questions to ensure the proper and best installation of your plumbing.
  122. Start-Up of a Swimming Pool: This is when all the pumps, filters, and heaters that require water are turned on for the first time.
  123. Preliminary notice: A subcontractor or supplier that delivers to or improves a property must file an initial note of intent to lien within 20 days after completing his work. Failure to file a preliminary notice of intent to lien will void his lien rights.
  124. Pump Apparatus: Pulls water from the pool and pushes through the filter.
  125. Raised bond beam: A raised swimming pool wall that is used to maintain a slope or to add cosmetic elements to increase the swimming pool’s design. A raised bond beam is usually made of stone or tile.
  126. Return lines: Inlets that allow water to be filtered into the pool. The best type of return system is a loop system in which the main return line circles all the swimming pools and several branches emit clean water under equal pressure.
  127. Scaled drawing: This is required in most states for any swimming pool construction contract.
  128. Shot Crete – The application of a wet mixture of sand and pea gravel to cement from a concrete batch plant under pressure.
  129. Skimmer: Sump with a leaf basket at the water’s edge. This is where you will find the main suction point for the pump and the filter.
  130. Steel Reinforcement – The installation of reinforcing bars (rebar) in the swimming pool structure according to approved engineering provided by the contractor. Most cities and counties don’t conduct a site inspection before issuing a building permit. However, it is up to the swimming pool contractor to disclose any conditions that may require exceptional engineering. Suppose the conditions are not disclosed, and the inspector fails to inspect the site. In that case, the owner is responsible for paying for any additional engineering or structure necessary to meet the site conditions. Ask questions and be careful.
  131. Stone Facing: Stone facing installed on walls with a raised bond beam or at a swimming pool or spa waterline. Each piece is flattened with grout joints.
  132. Surcharge: This is the pressure on the soil around the swimming pools, which requires a stronger swimming pool structure. The surcharge is at 45 degrees downwards into the soil at or near the swimming pool. A surcharge is addressed in engineering for swimming pools near houses; patio covers posts, slopes, or large boulders. If the pool is built on top of retaining walls, it can create a surcharge. This condition requires that either the retaining walls be designed and constructed to support the pool, or the swimming pool must be built freestanding so that the surcharge starts at the base of the swimming pool structure and ends at 45 degrees from the bottom of retaining walls.
  133. Unconditional License Release: Document signed by a contractor, supplier, or subcontractor to prove that the job was completed.
  134. Utility Route: The owner is responsible for the repair or reroutes costs if lines or sprinklers get damaged during excavation or trenching for a pool or spa. Ask questions and be careful.
  135. Waterfall – A water feature that can be found in many forms but is usually made from stone or boulders.
  136. Waterline Tile: A ceramic, porcelain, or stone material that covers the top six inches of the swimming-pool structure. The pool’s waterline is generally about half the height of the waterline tile.