Inconsistent backed-up drain?
Drain in furnace room backed-up in March. Water softener drains in here. Had it snaked. It backed up again 2 weeks later. This time they snaked from the toilet out to street (about 75 feet... not sure it made it to the street). All was fine until October. Last week when water softener recycle, furnace drain started backing up again. Then it slowly drianed itself. Waited until next morning and found out we could use all plumbing on half of the hosue fine (two showers and three toilets, including toilet they snaked iin March). However, when washing machine was used (other side of house), the drain started backing up again. Turned off washer. Waited 5 minutes for it to drain down. Started washer. Drain bubbled twice then all ran fine. Was able to run four loads of laundry and diswasher (bad side of house) with no problems. Each time we start something on bad side of house, drain in furnace room bubbles up once and then drains. Or rises a little out of its sides. If water is stopped (i.e. shut off this 2nd story shower), the water drains down and then shower is restarted and all drains fine. It's always clean water or we are just lucky. Back in March and also this time, we did have quite a few inches of rain prior to this occurring. Each time plumber came out in March, the drains were fine and water could be run down furnace drain, washing machine, and toilets with no signs of problems. Had it snaked anyway. Last week once again, it was draining fine by time plumber arrived. Ran lots of water down the furnace drain from the sprinkler outlet and all was fine. Didn't have the bubbling while plumbr was there either. Is this a blockage in pipe between furnace drain and main cleanout in basement for that half of the house? Or could it be a blocked vent? Plumber suggests camera in the line next time it happens. They want $350 for 2 hours worth of camera work. We want to figure out what's going on. Scared to plug the water softener back in.
Advice?
