Quantity of water flowing past a designated point within a specified time period, measured in gallons per minute (gpm).
Reinforcement bar, used to add strength to concrete. After excavation of an in ground pool, a steel cage is formed out of re-bar, and the gunite shell is shot over and surrounding it.
The chemical indicators used in testing water balance (all the little bottles or tablets in your test kit).
A reciprocating compressor or piston compressor is a positive-displacement compressor that uses pistons driven by a crankshaft to deliver gases at high pressure.
Usually refers to free available chlorine levels remaining in the pool after initial treatment or activity with contaminants.
The term used to describe a condition preventing full flow of water. Restriction can occur with full skimmer or strainer baskets, obstructions in the plumbing, dirty filter, undersized plumbing or equipment, or placing devices like heaters, cleaners or fountains in the circulation system. Restriction on the suction side creates higher vacuum (or suction), while on the pressure side creates higher pressure.