Couple of thoughts,
Does the pump unit have a filter in it? most do. Also I believe the side port is for drawing the fuel out, and the bottom port is to be able to drain and clean the tank. So if you attach a stand, and a valve on the bottom, then occasionally, you coulf drain off what has setled out, including the water, and keep the system clean.
What is the capacity of that tank? Might draw less questions by getting a HHO tank, the oval ones, they hold 275g.

__________________
83 300SD Dark Silver Dark brown inside

I worked for several years as engineer on tugboats, where a lot of one's day is spent managing fuel, cleaning, transferring, ballasting, etc.
I certainly wouldn't draw off the very bottom of the tank with your pump's suction-in fact, I'd tip the tank slightly away from the suction, so any water and gudge goes to low end. Then I'd make a stripping tube out of soft copper that can be easily bent around so that it goes to the very lowest part of the tank. Then once a week or so I'd take a little suction pump (like those squeeze-bulb siphon pumps that people use for kerosene heaters) and suck off any water, dirt, or black smelly fuel, which indicates that you've got bacterial slime in your tank. If that's the case, be VERY careful to get all the water out, because the bacterial grows at the fuel/water interface. Also, you might want to use a fuel fungicide. In my experience, Biobor is the best.
As far as legalities go, I think that in most places you're allowed to have a tank of #2 oil in your house, because so many houses are heated with it. There may be rules, including a requirement for a spill containment. If the code people were hassling me, I'd connect the tank to my heating boiler, and tell them that it was a heating oil tank. #2 is pretty much #2, as far as pollution is concerned.
SEO

The rust will not be a problem if you make sure no water is present. Otherwise cleaning and sealing it would a big PITA. You can get some water indicator paste (homer sells it) and put it on a broom handle and dip the tank for water. I agree with tilting the tank toward the drain plug and putting a ball valve there with some hose attached to a nipple or hose barb. Then open the valve before each delivery and drain the residuals before the fill. Cim-Tek offers filters for high volume pumps. There are others and google search will turn up plenty. Check what kind of volume and max psi your pump is pushing and pick filter that matches. Some guys use Mcmaster-Carr for all kind of fuel filters, fitting, hose, etc... Black pipe works fine.

IMO use some perservative and dispersant.Go to a health food store and buy a 300g bottle of Butylated Hydroxytoluene (BHT) powder. 3mg treats 10 gallons of gas so double this for diesel fuel. Costs under $10.00 a bottle. BHT is the active ingredient in fuel stabilizers, like Sta-Bil. Don't waste your money on that pretty red fluid in the fancy bottle.

__________________
1999 E300DT (131,800) 154,000 Black on Black SOLD

2006 CLK 500 coupe Capri Blue on Grey (zoom,zoom)
47,000mi

04 VW TDI Passat 80,000mi
(Techno)

How to eliminate oil dependency through market-driven approaches.
“We could cut oil use in half by 2025, and by 2040, oil use could be zero,”
The Sound of Diesel Speed
Ode to MB

Thanks for the replies. The pump I have is a Gasboy Model 390. I have found that rebuild kits are available for it, but no flow or pressure specs yet. If I draw from the outlet in the side of the tank there should be a few gallons left in the bottom to collect the scum. I will put a drain valve on the port on the bottom and make a cradle to support the tank for maintenance. Having a spill kit on hand is a good idea too. The threads on the drain outlet are a bit rusty but look solid. What type of thread sealant should I use that will stand up to biodiesel?

I think I should get a little oil heater for my garage now. The house furnace is in the attic, so no worries from ignition there.

__________________
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Any suggestions for a thread sealant? I got a 15 micron filter/water separator, some valves and hose yesterday. I hope to make a stand for the tank tomorrow.

__________________
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

PTFE Yellow Teflon Tape available at local plumbing supply or large box store.

__________________
1999 E300DT (131,800) 154,000 Black on Black SOLD

2006 CLK 500 coupe Capri Blue on Grey (zoom,zoom)
47,000mi

04 VW TDI Passat 80,000mi
(Techno)

How to eliminate oil dependency through market-driven approaches.
“We could cut oil use in half by 2025, and by 2040, oil use could be zero,”
The Sound of Diesel Speed
Ode to MB