Slow drain both toilets, sinks, everything
I am fearing that in an effort to save time, I plugged up the mainline. I flushed some clumping kitty litter. It plugged the toilet. I plunged it like a hundred times. It freed. Fine for a couple days. Then, toilets fill up, don't go down right away. In the upstairs bathroom, if you fill the sink with water all the way, then drain it, the toilet bubbles. If you plunge the toilet a lot, the shower drain bubbles. Downstairs toilet, same thing. Flush, bowl fills, then very slowly drains (takes about 2 min). When the washing machine downstairs is draining, or the dish washer, the kitchen sink gets a ton of loud air bubbles.
Is there something I can flush down the toilet or down the drains that can clear this, or will professional snaking equipment be a must? This is an old house, and a rental, and I really don't want to get the landlord involved. If I can fix this myself with chemicals, great. If not, how much will it cost, conservatively?
Thanks in advance.
Brian