I live in a one level house built on a slab. About 2 weeks ago we noticed that both toilets (the bathrooms are back to back) would bubble, gurgle and water would empty out of the bowl when the washer drained. If you tried to flush during this time, the toilet would overflow. The problem continued to get worse so I called a plumber. He found a clog in the line right outside the house and cleared it. This helped for about 2 days. Then, when my husband took a shower one morning, the toilets started acting the same way. Later that day as the washer drained, the toilets acted up, a lot of water leaked from the base of one of the toilets and the bathtub started filling up with water. I called the plumber again. They got their machine out and cleaned the main line under the house to the street (and a little bit beyond, I think). They said they hit something hard and were able to clear it. This again, fixed the problem for about 2 days. Tonight, the washer was draining and the toilets bubbled and drained again (but no water in the tub or out of the base of the toilet). What is going on? Before the plumbers came the second time I got up on the roof and ran a snake down the vent pipe above the washer and didn't find any problems. I didn't inspect any other vents, however. When I asked the plumber about the vents, he didn't think that could be the problem.