About this detail of the Tiger
Every Tiger 1 had at least two drain valves in the hull floor. They were used to remove liquids (usually rainwater) from inside the vehicle.
One valve was in the extreme rear of the engine compartment. The book "DW to Tiger1" shows it in a photo [1, see page 89] of vehicle #250002. Initially, this valve was operated via a latch on the rear decking, seen in the photo above.
At some point early in the production run the latch was deleted (possibly at hull #100 when other changes were made in the engine compartment). Instead, a handle was added to the firewall. The above diagram is a section through the hull, facing backwards. It shows the handle.
This is the handle in hull #250122, at Bovington museum  after restoration. (The original German markings were the letters "A" and "Z"; these words were painted by the restorers). The position marked "A" opened the drain, and the position marked "Z" closed it.
The handle was linked to the valve by a sheathed cable. The cable ran along the inside wall of the right-hand fan compartment, as these diagrams show. It was held by three hooks bolted to the wall. The cable's sleeve diameter was 10mm, and the travel was about 15mm.
This photo  shows the cable in vehicle #251114 (formerly at Saumur museum). The colours may not be original. This cable has been bent out of shape.
These diagrams show the position of the rear drain, behind the last torsion bar. The stiffeners on the hull floor had small holes allowing spilt liquids to reach to this corner.
The part number of the rear drain assembly  was "021 E 2702 U40". The first three digits, "021", identify the tank as a Tiger 1.
This diagram shows the mechanism for remote operation. The drain plug is mounted in a bracket identical to the one in the front hull. A second bracket is welded on top of that, carrying a hinged arm. The horizontal and vertical rods are spring-loaded. The control cable is fixed to one of the stiffeners on the hull floor.
This photo shows the brackets without the movable parts. This is vehicle # 250122  , during restoration in Bovington Museum. The drain is under the axle for the right-hand idler wheel swing arm.
This photo  shows a complete drain unit, in a tank built in June or July 1943.
In May 1944, starting from hull #251165, the rear drain was redesigned [1, see 220.127.116.11 and page 160] . The hole in the floor remained the same, but a simpler cable mechanism was used. The new part number was "021 B 2702 U 370".
The Tigerfibel  states that the rear drain should be left open when travelling, unless passing through water or mud.
The surviving Sturmtiger in Munster museum has only part of this drain mechanism. As the photo  shows, the handle has been completely removed from the firewall. This may have happened when the vehicle was converted from a Tiger. The control cable hs been removed from the engine room, and the drain hole retains only the plug and the lower bracket. Since the engine room was stripped of equipment after the war, I don't know the correct configuration.(The latest version of this article)