Shower pumps come in two configurations. Either a passive drain into a sump box with a float switch and a bilge pump to discharge from the sump box into either a grey water tank or overboard.
The other option is to connect the hose directly to an inline shower pump. The pump has a switch (usually lit) in the shower that is simply ON/OFF. The shower pan will flood until the pump is turned on. The pump will run dry when there is no longer water and needs to be manually shut off.
Check for 12VDC in this order
1) Inbound side of the switch
2) outbound side of the switch (with the switch on)
3) at the pump (with the switch on).
IF there is no power to the inbound side of the switch, there is an issue with the fuse (on teh fuse bus) or the circuit.
If there is no power on the outbound side of the switch, the issue is the switch.
If there is no power at the pump, it is the circuit from the switch to the pump.
If there is power to the pump, but it doesn't work then it is the pump.
Draining the shower into the bilge is going to create a horrible odor. It will also potentially clog your bilge pumps. I would fix the issue or start using a solar shower until its fixed.
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