Hello,
Is it possible he messed up something while installing the filter ?
Anything is possible. But there's a way to check.
With the filter dial valve in the Filter setting, take the cover off of the skimmer:
1. Is water moving in the skimmer?
2. Is water coming out of the return jet(s)?
If the answer to those questions is yes, the filter is plummed correctly.
What else I can do ?
You can provide more information.
Is this an above ground or in-ground pool.
If in-ground, is it a vinyl liner, a plaster/gunnite or a fiberglass pool?
If in-ground does it have a skimmer and a main drain?
How many gallons does it hold?
A complete set of chemical readings:
Free Chlorine
Combined Chlorine or Total Chlorine
Total Alkalinity
PH
Calcium Hardness
CYA (stabilizer)
Tell us if you took the readings yourself, (and if you did, did you use drop reagents or test strips) or if a pool store did the water testing.
J