Sink, tub, and toilet all back up

Quick Answer:

Stop using all plumbing fixtures right away. Multiple fixtures backing up while you run the sink usually means a blockage in the main drain or sewer lateral. Check nearby floor drains and utility sinks, inspect the toilet water level, and locate the nearest sewer cleanout. If you recently flushed non-dissolvable items, note that for the plumber. If sewage is present or you can’t access the cleanout safely, call a professional.

Why This Happens

When a single drain backs up, the clog is often local to that pipe. When a sink, tub, and toilet all back up at once, the blockage is usually in a shared drain line or the sewer lateral leading away from the house. Other causes include a collapsed pipe, tree roots, or recent construction that disturbed the line. If the problem began after work in the house, consider whether debris entered the drains. For patterns where both lavatory and toilet are affected at once, see Sink and toilet backing up together for related situations and causes.

Step-by-Step What to Do

1. Stop using all fixtures immediately

Turn off faucets, stop showers, and do not run any appliances that use water (dishwasher, washing machine). Continuing to use water can push sewage into fixtures and cause overflow.

2. Check nearby floor drains and utility sinks

Look at floor drains, laundry tubs, or basement utility sinks for the same signs of backup. If these are also filling or releasing dirty water, the issue is likely in a main line rather than a single fixture.

3. Inspect the toilet bowl and remove excess water if needed

If the toilet bowl is unusually high and looks like it might overflow, carefully scoop out excess water with a bucket or cup and deposit it into a floor drain or outside. Do this slowly to avoid splashing. The goal is to prevent overflow while you address the blockage.

4. Locate the nearest sewer cleanout and check it

Find the exterior or interior cleanout cap (usually a round or square plug near the foundation or in the basement). If the cleanout is full of sewage or you see sewage backing out, that confirms a main-line blockage. Only remove the cap if you can do so safely with gloves and eye protection—standing back and watching for pressure is wise. If you’re unsure, skip this step and call a pro.

5. Note any recent flushing of non-dissolvable items

Make a short list of anything recently flushed or drained (wipes, feminine products, cloth, grease, drywall dust). Tell the plumber exactly what was flushed—this helps them diagnose and choose the right tools.

6. Contain and clean what you can safely handle

Use towels or rags to block doorways and protect finished floors from sewage. Wear gloves and keep pets and children away. Do not use strong chemical drain cleaners on a sewage backup — they can be dangerous and usually won’t fix a main-line clog.

What Not to Do

Avoid repeatedly flushing toilets to try to clear a shared backup—this can cause overflow.
Do not pour harsh chemical drain cleaners into a system that may be full of sewage; they are hazardous and unlikely to clear a main blockage.
Don’t attempt to dig up a sewer lateral or access a buried cleanout without proper tools and knowledge. Instead, call a pro when multiple fixtures show sewage-backed water or you can’t access the cleanout safely.

When to Call a Professional

Call a licensed plumber or drain contractor if any of the following apply:

Multiple fixtures are backing up with sewage or foul water.
You find sewage at the cleanout or the cleanout is inaccessible or buried.
You suspect a broken pipe, tree root intrusion, or the problem began after recent remodeling—these scenarios often require cameras or excavation. If this happened after work in the house, see information on Multiple fixtures back up after remodel for common causes and steps your contractor should take.

Safety Notes

Wear waterproof gloves and eye protection if you must check drains or the cleanout.
Avoid direct contact with sewage. It can contain harmful bacteria and viruses.
Keep children and pets away from affected areas and ventilate any area with sewage odors.
If sewage has entered living spaces, a professional cleanup is recommended to properly disinfect and dry the area.

Common Homeowner Questions

Q: Can I use a plunger to clear this?
A: A plunger may help a local clog, but if multiple fixtures are affected it likely won’t clear a main-line blockage.

Q: Is this an emergency that needs immediate service?
A: Yes, sewage backups are an emergency when multiple fixtures show backup or toilets are overflowing. Call for professional help right away.

Q: Will septic systems behave the same as a city sewer in this situation?
A: A septic backup can cause similar symptoms. If you’re on septics, check the tank access and contact your septic service if the tank is full or you see sewage at cleanouts.