Bottom valve, looks like yellow neoprene(?) seal and small hole, the arm is connected to the underneath bucket which applies pressure to the hole? I'm making a guess here.
Side shot opened out
Top shot opened out
Side shot closed
Top Valve. This hole hear
I THINK is the hole that TTT might want to block, i'm not sure but i think this is the valve that controls the drain and refill part. by the looks of things i'm thinking they are 2 separate valves? One to fill untill it gets to the correct level and one to stop it filling while its draining.
Underneath hole, top valve
Osc u can confirm the autopots drain and fill? i played with them for an hour or so and it looked that way.
havent got the time TT but can have a play at the weekend to see if that valve does that.
hope these pics help? as mentioned the opinions are my own, might not be right. i'll have more of a play towards the end of the week as i'm using em 2 feed my girls plain water for the 2weeks flush
edit - and the new sofa's