I use the "GoldenRod" water-filter on my bulk tank. While its primary purpose is to remove water from the fuel before it gets into the equipt … it also has the ability to catch larger junk/paritlces so it does double-duty. The valve on the bottom of the glass is to drain any visible water or to take a sample.
My bulk tank is made from a 160 gal propane tank given to me by a friend. It is powered by compressed-air from my nearby hangar/shop which supplies regulated 10 psi of filtered/dried air. (See the blue regulator atop the system....the drier is inside the hangar.) Air passes thru the regulator, then thru a ball-valve, then to a "T" which allows it to enter the tank. Coming up inside the "T" to the top-reducer on the "T" is a dip-tube threaded/sealed to the reducer. The air pressure forces the fuel up that dip tube, thru another ball-valve then into the glass-bowl, thru the filter and then out thru the hose.
The dip-tube picks up fuel about 3" from the bottom of the tank preventing sediment/water from coming up the tube. (Notice that no rust/sediment/water has actually made it to the glass bowl so that plan is satisfactory.)
The long hose I already had (gratis) from a friend who got out of the marine refueling business and gave it to me along with the nozzle which explains the length, which allows me to refuel without the equipt having to be overly-closeby. I installed a set of hydraulic quick-couplers to disconnect the hose when I use my tractor FEL to load the tank onto my trailer for trips to the bulk-plant where I save 60-80 cents/gal on untaxed off-road dyed diesel.
I added a drain at the bottom of the tank so I can drain water from it or sample the bottom of the tank if I choose. (If the upper air-vent ball valve is opened and connected to the drain ball valve with a clear vinyl tube the level of the fuel inside is accurately displayed in the tube, but I haven't really need to do that, I just mention it in case anyone else is thinking of designing a system.) The system I designed so that the air-inlet/vent valves must be operated open in order to re-fill the bulk tank (prevents someone from opening the cap without relieving any residual tank pressure.)
Total cost of the system was less than what I saved on the first purchase of untaxed diesel, but the downside is the length of time before I use all the fuel. (I only operate three diesels...my tractor, a Ferguson 5-8B asphalt compactor-roller (repairs/smooths the damage to my grass aircraft runway made by wild hogs) and my RTV, so I treat the fuel with anti-fungal/biocide Biobor-JF and Stabil-Diesel.) Really saves all the messiness of handling/lifting/spilling cans.
The liquid seen is from a fresh rainfall, not leaking fuel.