Hot water switch on Seelevel Monitoring system

Simple on/off switch. Though unusual, they do fail.
Mine, a 709P3, doesn't have the WH switch, however the switch body is the same 3/4" X 1/2" size as the 3 way pump switch. The HW switch is just 2 terminal on/off. Pump switch is 3, on/off/on.
The pump switch might be removed from front but there are 2 ears that need to be squeezed and switch pushes out. Removing panel, the switch terminals could be momentarily jumped to verify its the switch.

I would expect replacements are available from Garnet - SeeLevel

Is the switch a rocker switch or a smooth push button like the ones to check the tank levels? If it's a rocker switch then yes it should be replaceable. Typically a rocker switch can be pried out of the front of the mounting panel panel. You might also remove the entire panel from the wall so you can see the back of the switch. There should be some spring tabs on the sides of the switch that when compressed will allow you to push the switch out the front. From that point the switch should be replaceable.