Nick,

You seem to love exhaust fans. It depends on where he is and the
humidity levels outside. If the dew point of the air outside is higher
than the surface temperature of the pipe im question, what you suggest
will not work. In fact, you will make it worse! Use a dehumidifier or
insulate the pipes or wrap them with heat tape. The heat tape idea
will work if the water flow rate is not too high. Try self regulating
heat temp. It is available in many temperatures and watt densities.

Stretch