Water coming up in the shower? Here's what's happening

Water always seeks the lowest path. In most homes, the drains from the shower, basin, toilet and washing machine come together somewhere in one shared pipe, which continues to the soil stack or sewer. If that shared pipe is blocked, the water you flush away in one place has nowhere to go. It then flows back to the lowest point it encounters. In many bathrooms, that is the shower drain, because it is flush with the floor.

What does it mean exactly?

If water comes up in the shower when you use water elsewhere, then the shower drain itself is usually not the culprit. The blockage is beyond the point where the drains meet. Think of:

• The shared waste pipe under the floor or in the shaft, to which toilet, shower and basin connect.
• The soil stack in a flat or apartment building, the vertical pipe into which several dwellings discharge. Read more about this in blocked soil stack.
• The house connection or sewer outside, for example due to a build-up of wet wipes, grease, root ingrowth or a collapsed pipe.

The more drains affected, the deeper the problem usually lies. If the drain in the utility room or outside is also draining poorly, there's a good chance it's in the house connection or the sewer.

When is it actually in the shower itself?

If the shower only drains slowly whilst you're showering, and nothing happens when the toilet is flushed or the basin drains, then the blockage is probably in the shower drain or the trap underneath. That's usually a matter of hair and soap. In that case you'll find a step-by-step guide in shower drain blocked.

What to do right now: step-by-step plan

1. Stop using water. Don't flush the toilet anymore, turn off the washing machine and dishwasher, and ask housemates not to run water for a while. Every extra litre can end up in the shower.
2. Clear away the dirty water safely. Backflowed water may be sewage. Wear household gloves, scoop or mop the water into a bucket and only pour it away once the drain is clear again; otherwise it will simply come back up through another drain. Afterwards, wash your hands thoroughly and clean the shower floor with an ordinary cleaning product.
3. Check which drains are affected. See if anything is also happening at the washbasin, the bath, a drain in the utility room or an outside drain. This helps determine roughly where the blockage is, and it's useful information for the technician.
4. Do you live in a flat? Ask the neighbours. If upstairs or downstairs neighbours also have problems, it's probably in the shared stack. Then also report it to the owners' association (VvE) or the landlord.
5. Check whether there's an inspection chamber you can access. In some homes there's a chamber with a cover in the garden or crawl space. If there's water standing in it, the blockage is further along towards the sewer. Don't remove anything yourself if you don't know how it's put together.
6. Call a plumber. A blockage in the shared drain or sewer usually can't be cleared with a plunger or hand snake from the shower. Professional drain unblocking equipment is needed for that, and sometimes a camera inspection to see exactly what's going on.

What you'd better not do

• Don't keep flushing to see if it clears. Each flush pushes more water back towards the shower, and in the worst case the drain will overflow onto the bathroom floor.
• Don't pour chemical drain cleaner down the shower drain. The product won't reach a blockage that's metres away. It stays in the pipe, is corrosive and attacks rubber and sealant. It also poses a risk to anyone who subsequently works on the drain.
• Don't use the plunger on the shower if the problem is in the shared pipe. You could then push dirty water up into other drains, such as the washbasin or toilet.
• Don't put a domestic pressure washer into the drain. It is not made for drain pipes and can damage connections. What is and isn't sensible is explained in unblocking the sewer yourself with high pressure or a snake.

Gurgling and sewer smell: often the same cause

Water coming up often goes together with other signs. The toilet gurgles when the shower empties, the drain makes slurping sounds or there is a sewer smell in the bathroom. This is because the air in the pipe can no longer escape properly and finds a way via the traps. Sometimes a poorly functioning vent is the cause rather than a blockage. Read more in drain or toilet gurgling and sewer smell in the house.

How to prevent it

• Only flush toilet paper and faeces. Wet wipes, sanitary towels and kitchen roll don't dissolve and are one of the most common causes of sewer blockages. See also what can go down the toilet.
• Don't pour frying fat or cooking oil down the kitchen sink. Fat solidifies further down the pipe and forms the basis for a blockage.
• Use hair strainers in shower and bath.
• Does it keep coming back? Have the pipe inspected with a camera. A subsidence or root ingress in the sewer cannot be solved by unblocking alone; sometimes sewer repair is needed.

Do you want to know who bears the costs if the blockage is in a shared pipe or the sewer? Then read sewer blocked: who pays? More about our working method can be found on the drain unblocking page.