Waste/Sewage System

I have done it several times with no problems . If it only last several years just dig another . I took a 55 gallon drum and shot a bunch of holes in it , buried it at a house in Port Orange Fl . It is still working 14 years later . RV toilets do not use as much water as household toilets which makes having a large leach field less necessary . Two drums connected aught to work good . I guess a lot depends on the type of soil , all mine have been in sandy Florida soil . Myself I would not ask permission .

I would get a large plastic tote, dig a hole going into it, run the plumbing to it, and bury the whole thing leaving a cleanout for pumping. Talk to someone about pumping it on a regular basis to find out the best way to set it up for access.

You will also have to insulate the line going from your black tank to the big tank, or it will freeze up in the winter. Do not leave the black tank open all the time to the big tank or you will get a big mound of poo that will plug up the black tank. Just dump it when it's close to full.

Truthfully for the gray water, just hold your use down and run it out a hose about 100 feet from the trailer. Beware, this may freeze in the winter too.

If the whole septic system thing goes south, consider using a holding tank, say 500 gallons maybe even less. Arrange with the local guy who does septic system cleaning to pump your tank on a regular basis. Have a contract with him... I have heard of this working on a temporary basis. The county IF involved may consider this, with a contract to empty/clean on a regular time frame.
This Might be better than trying to dig leach lines, but may be more expensive.
If you do this all "bootleg" this still might be a safer way of getting what you want to do.
Another option may be contacting your local "portapotty" guy he may be able to set you up with some kind of lower profile above ground tank to be pumped out by the portapotty guy.
Last resort just get a portapotty and run shower sink water out away from your trailer, I know in some counties in TX they can run their washing machine discharge on the ground .
Thats about all I got for you

I installed a plastic 55 gal drum with holes drilled in the sides starting about 15” from the bottom to the top. I sat the drum in a hole about 2’ larger in diameter than the drum. I lined the holes sides with plastic drain field mesh followed by filling the sides and top with 57 stone. Has worked as a separate tank washout and septic for family overflow from campers going on 12 years. Now it will not hold you dumping all your tanks at once but would hold a weeks worth of black water with no problem while letting the grays stay open all the time.

I'm pretty sure he just wants to bootleg a system....not for permanent use.

A DIY septic system is very likely not going to pass muster. Best to find out what is actually required by code before you do anything that will cost money.

You sound smarter than my nephew, a high school drop-out. He was able to build a septic system without any hesitation. They are simple in design. Having enough leach field might be your biggest concern.
Google is your friend here.

https://www.pinterest.com/pin/496733033879165021/

Another way to do it is bury a huge tank (250+ gallons) and have it pumped every so often, negating the leach field.

Oklahoma has statewide regulations relating to septic systems. You'll need to get a permit from the state, have some soil tests done, have various inspections and sign-offs, etc. Professional design is likely a practical necessity, if not actually mandatory. I don't know exactly how things run there, but here in Vermont you're generally talking about tens of thousands of dollars. Two 55 gallon drums and a drain field would definitely not be an acceptable here. Fines and penalties for non-compliance are significant, too.

See Title 252 of the Oklahoma Administrative Code Chapter 641, “Individual and Small Public On-Site Treatment Systems” for the details.