Little giant condensate pump.
Heat pump water heater condensate drain.
All piping is properly installed insulated sealed free of leaks and protected from exposed elements below freezing temperatures if applicable.
Not sure how they determine that your line is plugged whether it s pressure or some other means.
No problems so far i just run my condensate line to a condensate pump which then pumps the water to a drain in my basement.
The recommendation is to get a condensate drain kit for convenient draining and metal drain pans to protect the room where the heater is installed.
If the drain line gets clogged or the condensate pan is set improperly the water will run over and cause a leak.
If this pan becomes clogged with debris mold or even algae it could overflow and create a puddle around your pump.
Heat traps on inlet and outlet are properly installed.
Power vent and power direct vent heaters are equipped with the condensate drain so the water vapor from the exhaust gases will roll down the pvc vent pipe and through the drain port out.
Most heat pumps have a drain pan which is used to collect condensation from the unit.
I have a hp water heater as well.
Condensate drain lines are properly installed and piped to an adequate drain or condensate pump installed.