On a septic tank system why does washer water back up in a toilet near the washer and the other toilet cannot flush for up to 30 minutes after the washer water has drained?

Answer 1

It seems obvious that the septic tanks is too full, or overflowing, not allowing the waste water to go in. Water always wins, and when it has nowhere else to go, it backs up. Try having the septic tank emptied, which should be done regularly (every three or four years, depending on use). Also, if you use a powder laundry soap, it will form solid masses in the drain system, especially at bends, and they have to be removed. Always use liquid laundry soap to alleviate this problem. Although answer one may be correct, it is also possible, even probable, that the cause of the tank being full is that the "DRAINFIELD" [the perforated drain pipe and/or the adjacent ground around] has become plugged up and the effluent from the tank is extremely restricted. This results in backups when large volumes [as from a clothes or dish washer] of water are put into the system. Often this problem does not show up when smaller volumes of water[toilet flushing, showering, etc.] are involved. Another cause I've observed occurs even when there is NOTHING wrong with the septic tank OR the drainfield. This can occur when a small amount of water enters the system CONTINUOUSLY, as when a faucet with a bad washer allows a continuous flow into the system. In this case, the ability of even a good drainfield can be overwhelmed, and the tank remains full, and incapable of handling large volumes of water over short periods of time.j3h.