For the septic system to work,

The water they used must go through the drain field to go down. So it must allow more water to go down than what they used. If y know how much gal of water they use each day, y can call 3 to 4 contractors give y a price to do the work. The cost will vary from place to p, and from contractor to contractor. We just build a system for 4500. The other 3 contractor want 8000. So y can see the difference. It is up to y if y want them to move or not. All septic system have a limited capacity. As it gets older, the capacity will also go down. Good luck.