As supplied the Feldbahn locomotives carry water in a pair of interconnected one gallon tanks situated on either side of the boiler in front of the cab.  Although this is adequate for general use my experience of the Stafford variant of the locomotive showed that extra water capacity would be essential for timely running of passenger trains on my local society track at Pinewood.  So even before the Feldbahn was delivered I was thinking about how to carry water on my driving truck and feed it to the injectors. One solution would have been to install an electric pump to transfer the water from a tank on the driving truck into the existing tanks on the locomotive.  However this requires a reasonably sizeable battery to operate the pump, and if the operator forgets to switch it off the water overflows the loco tanks and is lost.  Having had experience of this first hand on my 4" scale Tasker traction engine (I dumped 6 gallons of water in Tewksbury high street while driving the engine in traffic) I opted for a direct gravity water feed to the loco's injectors. The photo on the left shows my hastily rebuilt driving truck which has become a flat bed wagon loaded with mixed cargo.  An old skip at the front holds plenty of coal, while the tarpaulin covered crates are actually a tool box and six gallon water tank. P.S.  Carrying six gallons of water proved its value in April 2015 when asked to help out at another miniature railway.  When a set of carriage brakes locked 'On' and the Feldbahn had to pull the loaded train around a 3/4 mile lap almost 4 gallons of water was consumed for that single lap.  A standard Feldbahn would have been out of water before it has got halfway round the track.

The photo on the left shows how simple push fit silicone rubber tubing is used to take water from the driving truck to the rear buffer beam of the Feldbahn, and the photo on the right shows how the pipe is bolted through the buffer beam.  By careful positioning the two pipes have been aligned so that they go straight into the rear end of the existing water valves under the footplate.  The original pipes from the two Feldbahn water tanks have been removed and the tank outlets blanked off.  This modification effectively reverses the direction of the water flow through the Feldbahns water valves so the injector piping required serious modification.  You can find out more about this on the injector modification page by clicking here. The copper pipes through the loco and truck buffer beams are all 3/8" outside diameter copper pipe and the silicone rubber tubing (sold by auto factors for use on car vacuum systems) is 8mm bore with a 2mm wall thickness.  Underneath the driving truck the two copper pipes are connected by more silicone rubber tubing to a "Y" piece and a 15mm diameter copper tube to the water tank outlet.

The 6 gallon moulded polyethylene water tank fitted to the driving truck was purchased from a caravan / camping supplier.  A suitable flush fitting filler cap with a 100mm diameter opening was also purchased and fitted to the top of the tank.  As I find it useful when driving to know how much water is left I fitted a water level indication system by installing five aquarium float switches into the tank, some of which can be seen in the photo on the left.  These switches have a magnet in the float which operates a reed switch sealed inside the body of the unit so no water can ever get into the switch assembly.  As the switches are available for less than £1 each on EBay they are a quite a bargain. The switch contact is closed when the float is in line with the body, so depending on which way up you mount the switch it can be either open or closed when the water level is "floating" the float.  I arranged the switches so that the upper 4 switches close when floating, while the lowest switch opens when floating.  The photo on the right shows the LED indications for the five float switches which are arranged so that the 2 green and 2 yellow LED's go out in sequence as the water level drops.  Finally the bottom red LED will light up when the tank has about 1/2 a gallon of water left, which really is time for the driver to stop and fill up. Power for these LEDs and the loco / driving truck lighting controlled by the switch beside the LEDs is provided by  7.2 volt radio controlled car NICAD battery packs.