How do i get to the shower drain

the grey water is your shower and sink drain tank. the black water is your... you know. the two combine to the dump that's held together with a bypass for grey water to flow into the black tank and vice versa so you can flush the black tank further. all of this comes out the end into your dump out for black and grey. If your talking about white water (potable) holding tank, filling this drains through the use of it, run the shower outside or hold flush down until it drains. otherwise. the hotwater tank will drain with the anode when you regularly change that once a year as directed by people who camp once a year - change that anode -

The first thing to do is to drain the fresh water tank. Drain the hot water heater. Install the RV antifreeze by allowing the water pump to be pumped into the water lines by opening the valve for this process. Open each water valve on all the sinks and the toilet valve as the RV antifreeze is being sucked into the water system and run until the color changes to the color of the antifreeze. Allow each trap to have antifreeze in it also, sinks, shower drain etc. Remove the inline water filter if one is installed and install the bypass plug in its place.

I actually am not able to get rid of the antifreeze taste from the water system so I blow air into the hot water tank drain at a low pressure until all the valve at each place water is controlled. Do not forget the outside sprayer and the shower hose and the shower head.

I allow the pressure to build up to 20 psi or so and then go into the unit and open each faucet until all the water is pushed out of the lines. Then I dump antifreeze into each P trap. Do not use the antifreeze used in the engine cooling system but the non toxic type made especially for RV water systems.

If it is a big valve it is your sewer tank drain valve. There is two valves. One is the Black water drain and the other is the gray water drain. the black water drain comes from the toilet holding tank, and the gray water valve drains the shower and sink holding tank.

Assuming you mean you're going to park it for the winter ????
Start by draining all the water tanks, i.e., fresh water, grey water, black water. Go inside and open all the faucets - if you have one or more where it's a common lever type valve and you swing it left or right depending on desired water temperature, then set it for the middle and turn it full on - leave all faucets turned on - shower included. This will allow the water lines to drain out. DO NOT TURN OFF the faucets - leave them on. Don't forget the toilet tank. If there is still some water left in the bottom of the toilet, pour in a cup of standard automotive antifreeze (ethelyne glycol type) and then CLOSE THE LID of the toilet. Ditto this (antifreeze) for all of your drains. Pour 1 cup of (full strength) liquid antifreeze into all drains (sink drains, shower drain, etc) Finally, make a sign that says "WINTERIZED - PLEASE DO NOT USE" and then TAPE THIS onto the toilet lid.

need to check connections going to shower. turn on water and see if runs down lines. also try to reach up to the sink connections a do the same. they tend to come loose. should be able to hand tighten. also check behind toilet at connection.

Is it leaking at a glued connection or a jam nut connection? If at the jam nut connection you may need to replace the jam nut washer to get a good seal. If it is a glued connection. You may get luck and reseal the connection by swabbing some ABS glue over the leaking area. ABS glue is thick black glue and may be found at your local RV dealership.

Make sure you have enough water in the tank or city water hooked up. A pump will run and suck air if the level is low. it could force water to the sink, etc, but not the shower.

Are your valves for the water pump set correctly? Remote possibility someone installed a shut-off valve between the pump and shower.

Could be the pump is getting weak/leaking internally and can't build enough pressure.

Make sure the shower head is not clogged. Remove it from the hose and try again.

You may have a very small access panel on the front of the shower pan or through an access point in a cabinet on the backside of the shower wall. I have seen the shower tail piece get cut too short and as a result is becomes disconnected from the "P" trap under the shower.

The best way to repair is to completely remove the shower surround and pan. Build a better support and repair the drain then reinstall. Leaking water will ultimately ruin the actual floor of the camper.