(651) 228-9200Schedule

All Articles

Why Is Water Backing Up in My Bathtub When I Flush My Toilet?

The scenario: When you try to flush the toilet, it doesn’t flush and water comes up in the tub. The water in both places goes down after few minutes.

The most likely cause: A partial sewer line clog in your bathroom’s drain.

Let’s look at how a sewer clog causes this problem and what you can do about it.

How a sewer line clog causes this problem

Your toilet drain and bathtub drain (and likely the sink drain, also) all feed into the same main sewer line.

sewer lines

Think of your drains like a river and its tributaries. Small rivers converge into one large river. The main drain is much larger than the individual lines, so it has no problem handling your toilet normally.

clear drain line

But when your sewer line is partially clogged, that large volume of water from flushing your toilet can’t get down the drain fast enough and some of it diverts up your bathtub’s drain.

clogged sewer line

Since the drain line isn’t completely clogged, the water empties out of the toilet and bathtub after a few minutes.

OK so now that you know what causes your toilet to backup into your bathtub. But what can you do about it?

What to do about a sewer line clog

First, don’t bother with plunging. No amount of plunging will dislodge the clog in a sewer line. The clog is too far away. Plungers are for clogs in the toilet itself, not the sewer line. Plus, the most likely causes of a sewer clog are:

  • Tree roots
  • Flushed toys or feminine products
  • Grease buildup

Those items don’t move easily. And in the case of tree roots, the roots need to be cut out of the pipe and the pipe will need to be repaired.

You’ll need a closet auger. A closet auger is a type of plumber’s snake with a protective cover to keep from scratching the delicate porcelain toilet. If the clog is further down, you may need to remove the toilet or use one of your cleanouts to get to the clog.

We also recommend doing a video inspection of the drain to ensure that the cause of the clog has been completely removed. Otherwise, you could have the same problem again in a few days or weeks.

Want a professional plumber’s help?