Ace Pelizon Plumbing was called out on a shower getting no hot or cold water. Ace Pelizon Plumbing found shower had no water at all. We removed the shower valve and still no water. We used a fish tape to go through 1/2 pipe and saw that the tape stopped at the couplings. The couplings were actually check valves that were installed backwards. Customer did his own work on that side. This was not a recall on work that was done in March. After investigation we figured out it was indeed customers own work why shower was not working properly. We will cap lines for the customer as recommended and requested. Options were presented to commence work on shower valve but customer refused. Ace Pelizon plumbing used couplings and shark bites to cap lines. All equipment is working properly. We assisted customer on installing the shower head. Work area was thoroughly cleaned.