Water Coming Up Through the Shower When the Toilet Is Flushed

Flushing the toilet and seeing dirty water appear in the shower tray is unpleasant, but it is a useful clue. It almost always means the blockage is not in the shower or the toilet, but further down the pipe that they share.

Why it happens

Your toilet and shower usually drain into the same pipe or underground drain. When that pipe is blocked downstream, the water from a flush has nowhere to go, so it comes back up through the lowest open fitting connected to it. Shower trays, especially on the ground floor or in wet rooms, are often the lowest point.

What it tells you

• The blockage is beyond where the shower and toilet join. Clearing the shower waste will not fix it.
• It is likely to get worse. If the drain blocks completely, sewage can overflow from the shower or a downstairs toilet.

What to do now

1. Stop flushing and avoid using water in the house, including the washing machine and dishwasher.
2. Clean the shower tray with disinfectant, as the water contains sewage. Wear gloves.
3. Check the inspection chambers outside, if it is safe to lift the covers. A full chamber means the blockage is further down the drain. An empty chamber nearest the house means the blockage is between the house and that chamber. See how to find your drains.
4. Ask your neighbours whether they have problems too. If several houses are affected, it may be a shared drain or public sewer, which is usually the water company’s responsibility. See blocked drain: Southern Water or me?

Can I fix it myself?

If the blockage is in an accessible underground drain and you have drain rods, you may be able to clear it. Our guide on how to unblock a drain explains how. Do not use chemical products, which will sit in the shower tray and make it hazardous to clear.

When to call

Call a drainage company if you cannot find or reach the blockage, the chambers are full, or water is close to overflowing. This is usually a straightforward job for drain unblocking, and the cause, such as wipes or grease, can be found so it does not keep happening.

See also why does my toilet keep backing up?