Why Is Water Backing Up In My Bathtub?
Standing in ankle deep water while trying to take a shower is frustrating, and it's usually a sign of a blockage somewhere in the drain line. Water backing up in a bathtub can range from a simple clog you can clear yourself to a more serious issue further down the plumbing system. Here is what typically causes it and how to tell which one you're dealing with.
Key Takeaways:
Hair and soap buildup in the drain is the most common cause of a backed up bathtub
Maricopa County's hard water contributes to mineral scale that narrows drain pipes over time
Slow drainage limited to the tub often points to a clog in or near the P-trap
Backups affecting multiple fixtures at once suggest a blockage further down the shared drain line
Root intrusion or a damaged sewer line can cause backups that worsen gradually and should be evaluated by a plumber
1. Hair and Soap Buildup in the Drain
The most common cause of a slow or backed up bathtub drain is a clog made up of hair, soap residue, and skin cells that accumulate along the walls of the drain pipe. This buildup narrows the pipe over time until water can no longer drain as fast as it enters, causing it to pool around your feet during a shower. This type of clog is usually limited to the tub itself and does not affect other fixtures in the home.
2. Mineral Buildup Narrowing the Pipe
Maricopa County's hard water, which runs 12 to 18 grains per gallon, contributes to mineral scale building up inside drain pipes over time, similar to the way it builds up on fixtures. This buildup narrows the interior diameter of the pipe, making it easier for hair and soap to catch and form a clog, and slowing drainage even without a full blockage present.
3. A Clogged P-Trap
Just below the tub drain, the P-trap holds a small amount of water to block sewer gas, but it can also catch and trap debris that makes its way past the drain cover. If water is slow to drain but does not affect any other fixture in the bathroom, a clog sitting in or just past the P-trap is a likely cause.
4. A Blockage Further Down the Drain Line
If water is backing up in the bathtub and you notice slow draining or gurgling in other fixtures at the same time, such as the sink or toilet, the clog is likely further down the shared drain line rather than isolated to the tub itself. This often points to a blockage in the branch line connecting multiple fixtures, or in some cases, a partial clog in the main sewer line.
5. Root Intrusion or a Damaged Sewer Line
In older East Valley neighborhoods with mature trees, tree roots can grow into small cracks in underground sewer lines, gradually restricting flow and causing backups throughout the home, not just in the bathtub. Clay soil movement common throughout the area can also cause pipe sections to shift or crack over time, contributing to slow drainage that seems to worsen gradually rather than appearing suddenly.
When to Call a Plumber
A simple hair clog is often manageable with a drain snake or a thorough cleaning, but if water backs up in multiple fixtures at once, if the problem keeps returning shortly after you clear it, or if you notice gurgling sounds from other drains when the tub is used, it's time to call a plumber. These are signs the blockage is further down the system than a household tool can reach.
For 45 years, Superstition Plumbing has helped homeowners across Mesa, Scottsdale, Gilbert, Chandler, Queen Creek, and the surrounding East Valley communities clear stubborn drain backups for good. As a family-owned company, we use leak location and drain inspection equipment to find the actual source of a backup rather than guessing. If your bathtub keeps backing up, give us a call.
