Don't know about Panasonic, I help my mom replace a Joven instant water heater with pump, the installation manual state "Cannot have centralized pump"

To check pump problem or leaking problem, turn off the ball valve at the pump's outlet, if stop means pipe problem. Then, open back the ball valve and turn off all the stop valve in your bathrooms c whether it stops, if it does that means one of the bathroom got problem. Turn back on the stopvalve for 1 bathroom only, wait for 3-5 min to c whether the pump is running or not, if no then continue to the next bathroom.

The sales guy got demo and explain to me.
The pump with air tank will not start immediately once you use water. It only start 30 - 60 sec after turn on ur water tab. n feel less vibration.
The pump without air tank will start immediately once you use water. n feel more vibration. (pump will turn on even u just wash hand for 2 sec)

So I get the pump with air tank.

By the way, we need to pump in air to maintain the pressure (psi) of the air tank yearly. (If no more air in tank...then ur pump will rosak)

Hope this info helps u...