sewer line restriction?

[John D.]

I’m in the process of remodeling the downstairs bathroom of a raised ranch home. After removing the toilet, I noticed that if anyone flushes a toilet upstairs, the water rises in the exposed sewer line to within a couple inches of the floor. The level then goes down as fast as it rose. This all takes place in about 10 seconds.

There is little or no water noticed if the upstairs bath tub and sink is run on high or if the washing machine or dishwasher is discharging. If I take a garden hose on full to the opening, I don’t see any backup. I only notice this when a toilet upstairs is flushed.

Is this indicative of some restriction in the sewer line? One plumber said there should never be any rise in the water level. Another said that’s to be expected.

My question is, is this normal?
Or does this indicate a restriction in the sewer line?

This point is the lowest point of the house. The sewer line is just below the slab floor.

[jnaas2]

If a tee was installed where the toilet upstairs connects to the line downstairs instead of a y with a 45 degree bend you will get a backup in the line from the flushing of the toilet because of the large rush of water hitting the line. Tees are supposed to only be installed in the verticle position when the water gets to the tee gravity pulls it down the drain line, if you lay a tee on its side where you connect 2 horizontal lines together the water will enter the tee and hit the far side of the pipe some will go in the right direction and some will be forced in the opposite direction. If the tee is installed in a horizontalm line with a line from upstairs connected to it the water will do the same thing it will be forced in the wrong direction, this can cause trouble but I wouldnt worry about it to much unless you have trouble with the line clogging up