Do some simple testing. Put a hose on the tap. Raise the hose up 2 meter with a stick. Open the tap and see the water flow out good enough.

You need to know, how good is good the pressure. Something a figure to see, check and measure. Without this, the lady boss thinking preesure is not what you think the pressure is it. So you got to ask yourself, how to tell.

Got to try to avoid the later argument with the boss if mistake buying the wrong heater.

Just replace to new 1 not enough. As you see in this few case, the heater doesn't protect you at all. You don't no when is the right time to change it. Or when is the time to take your life.   Quite scary.

You need a third party safety device to protect you. 1 fail, still got another 1 to protect.