I just checked my Uv sterilizer bulb, closed loop getting 400-500 GPH. I run it 24/7. I havent changed it for almost a year is that a reason for the burn out?
The bulb should last at least a year. Do you turn off the UV often? The ballast supplied (2 wire instant start) will wear out the bulb rapidly if the bulb is turned off and on too much.