Let me try.
The water outlet on the side of the tear has an on/off valve just like the valve on the grey water tank drain. This is where you would put the sprayer hose. If you remove the sprayer hose, or any outgoing hose, water will just squirt out here when the pump is turned on unless you turn off the valve. If you leave the valve on and lock the door it will run down the side of the tear until empty.
The water pump does not pressurize the tank. It will not blow back out any of the fills. It will only come out the faucet or the water OUTLET.
Moral, when you go to unhook an outlet hose, turn the valve on IT off first.
Hilditch