If water come out of the waste pipe line while the multi port valve is on any other position except on waste, then it is 90% of the time the seal (wagon wheel) is worn or damaged. There is normally three reasons for this failure.
- A worn out multi port valve top.
- A worn or damaged seal.
This is due to solid partials like sand that went through the multi port valve and the wrong way of operating the multi port valve.
It is really not that difficult to check or change the seal. Make cure that the power supply is off. Loosen the six bolts (mind the nuts underneath) around the multi port valve. remove the top end of the valve and inspect the seal.
If your not sure how to do it, rather call your nearest pool technician to repair it for you.