Equipment:
VFD - Variable Frquency Drive. A type of motor for variable speed pumps
GFI/GFCI - Ground Fault Circuit Interruptor. An electrical circuit breaker that opens when a circuit is shorted to ground

Chemicals:
DHMO - DiHydrogen MonOxide - Water

InterWeb cliches:
OP - Original Poster
BTW - By The Way
IMO - In My Opinion
IMHO - In My Humble Opinion
LOL - Laughing Out Loud
ROFL - Rolling On Floor Laughing