Acrylic: a product used to make hot tub interiors
Air Leak: what happens when a pump has a crack on the suction side so it draws air into the water. This can damage the pump and the filter. If your water has a lot of foam and anti-foam isn’t working, this could be the reason.
Algae: microscopic plant life that grows in unbalanced hot tub water where the cover is off a lot
Alkalinity: (see Total Alkalinity) a measure of how much buffering agent is in your water
Anti-foam: a chemical which reduces or eliminates foaming.
Biguanides: (pronounced By-GUAN-eyed) sanitizer that is part of a non-chlorine and non-bromine water treatment system.