Here is the Bilge Pump I use:
http://i700.photobucket.com/albums/ww9/mxfive_photos/Gold Prospecting/056.jpg
Never had a problem with this bilge pump they just keep on keeping on, it can run all day on a single charge. I just run it of the secondary battery from my Troopy. Just go for a drive to recharge the battery if needed.
Remember trapping the gold is all about water flow get it wrong and you will be losing gold out both ends of the high banker. You do not want a flood of water, you want to setup an eddy current that looks like a sine wave going over the riffles, it's the eddy current that will allow the gold to drop and get trapped by the riffles and matting.
I bought my high banker from Bruce Bertram at Warwick, he is a top bloke and he has perfected this high banker design over many years. Here is his number if you are interested in getting a high banker built 0423-659-001.
First thing to do is buy a level and use it to make sure your high banker is level on the ground both length wise and breadth wise. Then get your angle right about a quarter of an inch drop then secure it with rocks:
http://i700.photobucket.com/albums/ww9/mxfive_photos/Gold Prospecting/0b523ae2.jpg
Next you need to adjust your water flow so it shows up bubbles like this between the riffles:
http://i700.photobucket.com/albums/ww9/mxfive_photos/Gold Prospecting/0f277d5f.jpg
I use a pan underneath it and fly mesh around it to keep it from clogging up with silt and debris:
http://i700.photobucket.com/albums/ww9/mxfive_photos/Gold Prospecting/c51157ba.jpg
Here is the Astro Turf matting I use, its great catches even flour gold:
http://i700.photobucket.com/albums/ww9/mxfive_photos/Gold Prospecting/0f0748f7.jpg
Here is the Classifier built into the hopper:
http://i700.photobucket.com/albums/ww9/mxfive_photos/Gold Prospecting/6eff8e7a.jpg
Here is an example of the gold it traps right down to the flour gold:
http://i700.photobucket.com/albums/ww9/mxfive_photos/Gold Prospecting/b2454837.jpg
Since these photos were taken I have replaced the black hose with some stronger reinforced hose that doesn't kink.
Never had a problem losing any gold from this high banker I have panned out the processed material after running it through the banker a few times now and have never found anything that it missed.
Also if you find you are getting gold in the last couple of riffles then your angle is way too steep as the gold should typically be trapped in the first three riffles only and mostly in the first one.
I also set the high banker up at home with the bilge pump sitting inside a large plastic tub full of water and just recirculate my water so I can process any material I have collected in the field. Also setup this way if there is little water left out in the field.
Hope this helps.