Hi Mike--while I applaud your attempt to be proactive, I think you are worrying about something for nothing. Your Mother-in-law will have very little impact on your already existing septic system. If you can't or won't pipe her RV in to your system, consider using a portable tank that you could dump in to any access point in your system. If that doesn't work, consider purchasing a macerator system that could pump the sewage (probably not more than a couple of times a month) in to a toilet in your house. If all else fails, you could have her not use the drains in her RV and simply use the house facilities. Maybe even consider using a cassette toilet in the RV which could be emptied in the house when needed. Remember, there are no problems, only solutions! Good luck!
