You can also buy Frontline or Advantage online at something like PetMeds.com
You sure you turned the valve completely open at the hot water tank after you were finished? I know you probably did, but sounds sorta like your tank isn't filling up fast enough. I only bring this up cause once we shut off the water....but didn't completely open the hot water valve...and ended up needing to replace the electric heating element on our water tank. It was a 'DUH' moment in our house. Course, Dave has a zillion valves for shut-offs...no wonder a gal gets confused!