A couple weeks ago my sinks, toilet and tub were gurgling and draining very slowly. I called a plumber but by the time he came, the gurgling and slow drain had stopped. He said all the drain lines were clear. He even snaked out the line from the house to the backyard and said there wasn't any obstruction.

Today the problem started again. When the tub is draining, there is loud gurgling in the sinks and bubbles coming from the toilet. The drains are all slow and the toilet even overflowed once. The plumber never mentioned the vent pipe at the top of the house but from what I've looked at online, I'm wondering if that could be it. How do I check? I can't really afford the plumber again. :(

Thanks,
Abby

"Bubbles" and "Gurgles". They are both indicters that something's going on in your drainage system.
A "bubble" indicates a clogged line while a "gurgle" indicates a blocked vent. Let me explain. When you flush the discharge drains down the pipe until it hits a partial clog. Then it rebounds back sending a "bubble" of air ahead of it. When you flush a toilet or drain a bathtub a suction is created by the water rushing down the pipe. This suction is relieved by a open pipe that runs to the outside called a vent. When a vent's stopped up the suction has to relieve itself somewhere, in this case your toilet. The noise you hear is the air being pulled through the trap by suction, (gurgle).
Since you have both it sounds like you have both a vent AND a drainage problem.
Are you prepared to snake the lavatory roof vent? Because that's the first thing I would do. Regards, Tom

Thanks Tom. You were right. We snaked the vent because looking into it, we could see water at the bottom. Once we snaked it, the water went down but whatever we loosened went into the drain and then nothing could go down. Called a plumber (overtime weekend :( ) and he used a big power snake all the way out the drain and across the backyard. No more bubbles, gurles or slow drains.

One last question: the plumber suspects that there may be roots getting into the pipe in the backyard and suggested "Ridex" down the drain. He said it will attach itself to the roots and kill them. In your experience, does this type of treatment work?

Thanks again for your help!

Abby