bubble magus dosing pump help

[uchin]

the calcium pump is losing prime and line stays empty. i have to manually prime the line to dose. anyone know why? i think its back syphoning.

 

[Clearwater]

Could be a hole in the line and have to replace the head. I had that problem when I first got mine and BM sent me a replacement. I would try to detach the head from the unit clean the line with some water. Put your finger on the short end and blow in the other. If air is coming out and not holding pressure time to replace the head. Good luck!