- Turnover time
- The longest time allowed for a pool's recirculation system to move one full volume of its water through the filter. It starts every circulation design: divide gallons by hours and minutes to find the slowest allowed flow, which varies by pool type.
- Total dynamic head
- The combined resistance a pump must overcome, in feet of water, from friction in pipe and fittings, the filter and the lift. Pump selection compares head and flow on a curve, and a filter type may carry its own minimum head.
- Skimmer
- A weir-type fitting in the pool wall that pulls surface water and floating debris into a basket before the pump. The count depends on surface area and flow, and its operating range defines the working waterline.
- Hydraulically balanced outlets
- Two or more suction fittings piped symmetrically so each draws about equal flow, separated by a minimum distance. If one is blocked the other still carries the pump, which prevents a single blocked drain from holding a swimmer.
- Anti-entrapment cover
- A listed grate designed so its shape and flow area do not trap hair, limbs or body parts. On private pools covers must be fastened so they cannot be removed without tools, and suction fittings must meet the entrapment standard.
- Backwash
- Reversing flow through a sand or DE filter to flush trapped dirt out to waste. The piping must handle a flow much greater than normal filtering, and the discharge goes through an indirect connection, never back to the pool.
- Diatomaceous earth filter
- A filter that coats grids or fingers with fossil algae powder to trap very fine particles. It runs at a low flow per square foot of area, needs recharging after backwash and sends its spent powder to a separation tank.
- Cartridge filter
- A filter using replaceable pleated elements that are cleaned by hosing rather than backwashed. Because it tolerates only a very low flow per square foot, it needs far more surface area than a sand unit for the same pump, and spare elements are kept on hand.
- Gunite
- Concrete shot at high speed through a hose by the dry-mix process, with water added at the nozzle, to form pool shells over the steel cage. Skilled nozzle work packs it around bars and yields dense walls that must then be kept moist to cure.
- Rebound
- Sprayed concrete that bounces off the surface instead of sticking, mostly coarse aggregate. It must be cleared away rather than worked back into the shell, because trapped rebound makes weak pockets and voids.
- Equipotential bonding grid
- A network of connected conductive parts, including reinforcing steel, metal equipment and fittings, tied together to keep them at the same electrical potential. It lowers shock risk in and around the water, and its tie points are made during steel placement.
- Hydrostatic relief valve
- A spring-loaded plug in the pool floor that opens to let groundwater enter and equalize pressure when the pool is emptied. Without it, high groundwater can lift or crack a shell, so it matters for draining and renovation work.
- Bull-nosed coping
- Rounded edge material set on the top of the pool wall, projecting a short, limited distance over the water. It gives swimmers a place to grip without a separate rail and sets the coping thickness that affects the shell's top elevation.
- Cantilevered decking
- Reinforced concrete deck that extends past the pool wall to serve as the handhold, with a rounded edge and limited projection. It is poured with steel tied to the beam and sloped slightly away from the water.
- Depth marking line
- A contrasting band of slip-resistant tile across the floor at the point where the water depth reaches the shallow-to-deep transition. It warns swimmers where the floor starts to drop and is omitted only in very shallow pools.
- Break in slope
- The line on the pool floor where the gentle shallow-end grade changes to the steeper one toward the deep end. Its location is defined by water depth and it is shown on the plan, and markers on the deck must identify it.
- Wet-niche light
- An underwater fixture mounted in a niche in the pool wall with the lamp surrounded by water. Its branch circuit needs ground-fault protection, and a public-pool fixture needs sealed terminals and licensed electrical work.
- Safety pool cover
- A manual or powered cover that meets a recognized strength and safety standard, so a child or adult stepping on it will not fall in. It counts as one of the drowning-prevention features for a new residential pool, though not when paired with a pool alarm.
- Title 22
- The state regulations section that sets health-department rules for public swimming pools and spas, such as water quality, safety equipment and operation. A commercial pool must satisfy it in addition to the building and electrical codes.
- Heat pump pool heater
- A heater that moves heat from outdoor air into the water using a refrigerant cycle. It is one of the energy-code compliance routes for pool heating, and its performance falls when outside air is cold.
