Water line drain on Quantum LF31

[JMR]

Hi!
New owner of a used Thor Quantum LF31 I'm getting ready for winter and started identifying my water line components (tank, drains, pump…).
I found 2 drains w/ valves under the fridge, and others near the water tank under the bed.

I took pictures of the area under the bed because a few points raised my attention (I noted them 1,2,3,4 on the pictures).
Can you please confirm my understanding and help with the questions I have?

1. This one is connected to my freshwater tank drain on the side (black plastic faucet). Use for that one seem clear to me.
2. I'm not sure about that valve in 2. Is it a main water shutoff? It is connected to the water pump, so I guess it must be my main water line.
3. That pipe goes upward and is closed by a white plastic plug. Can anyone point to the use for that? Pour antifreeze in the water line may be?
4. That valve was hard to find and is under the heating duct below the fuse box. It seems to be my tank's low point drain. Correct?


Anyone knows if there are other water drains that I need to identify?

I also discovered there is a water filter that I wasn't aware of. It's a weird location but changing the cartridge should be ok (I don't want an old cartridge full of bacteria to remain on the water line).
Is it filtering only the water from the freshwater tank? Just to know if the filter that I usually put on city water is useless.

Thanks in advance for your answers. I'm now going to research my water heater bypass, which I guess is somewhere under the sink (nothing seems reachable from the outside panel).


JM

[JMR]

Actually I got all the answers I needed through the Thor documentation that someone pointed me to in the welcome section. Thanks anyway.