I live in older house (1930's). I recently found that my washer and utility tub drain into the basement floor drain which drains out 70 feet towards nowhere (leach field not city sewer/water). Lately, the washer has been backing up in the basement after a wash or two. Had plumber look at the lines - this is how I found about the leach field. He suggested that I move washer and tie into the existing main waste line. From what I've been reading, I don't think I can do this as there are two main lines coming from upstairs (1 first floor/1 second floor) that join at the basement ceiling a exit through the basement floor. One line in ceiling has 2nd floor tub/sink/toilet attached and I do not believe that this line is vented to roof (old house). The other line has shower/sink/toilet attached and I believe IS vented. From what I've read, I cannot tap into the main waste line as the washer line I would be adding cannot be vented and I would be running a toilet past a non-vented line!? Any suggestions for options?
Upon reading more, I noticed that someone suggested a studor valve. Would this be possible? Would it be possible to have the washer next to utility sink and still have a standpipe (ie both)? Any suggetions on where I could find diagram with pipe sizing? The run to the main waste line is about 10 feet. Thanks

If you live out in the county, at least in the south it is common and seen all the time for the washer to drain off into the yard at some point ( normally a area for water flower garden) Part of this was to put less water ( that had no waste) into the septic tank. Esp since historicly many farm and rual families had large family and did a lot of washing

So unless this has been an issue I guess I have to ask why the leak is just not fixed and you keep using it where it is.

How did the plumber suggest doing it? How much was he going to charge?

Plumber suggested that I move the washer and line but did not offer any suggestions or bring up the potential problem with venting. I do not live in the country. I live in the city. It appears that when sewer was put in years and years ago, it was common practice to run floor drain to leach and to drainage around the house.

Upon closer inspection, the second floor main line IS vented through the roof. However, venting the wash/utility tub from basement still isn't option.

The water in basement is a new problems that began last spring and has gotten worse since then. It occurs with more and more frequency. I had a plumber out to fix the problem. They augered both the main line and this "floor line". It was at this point that they found that the floor line went out to sand and gravel and did not connect to main sewer. This was verified with camera.