If you have looked at bath traps, you will have seen the term "shallow seal". It describes how much water the trap holds in its seal. Because baths often sit very close to the floor, shallow seal traps are one of the most common choices for baths.
What Is a Water Seal?
Every trap holds a small amount of water in its lowest point. This water, called the seal, blocks drain gases from coming back up through the plughole. The depth of the seal is the height of water that sits between the drain side and the room side of the trap.
Shallow Seal vs Deep Seal
- Deep seal traps hold a deeper column of water. The extra depth gives more protection against the seal being pulled out by pressure changes in the pipework, but the trap is taller.
- Shallow seal traps hold less water, so the trap body is shorter. This makes it easier to fit under a bath, where the gap between the bath and the floor is often small.
Why Shallow Seal Traps Are Used Under Baths
Most baths sit on feet or a frame with only a small space underneath. A deep seal trap may simply not fit. A shallow seal trap gives a working water seal in a much lower profile, which is why it is a common choice for bath installations.
Shallow Seal Traps on Freestanding Baths
On freestanding and roll top baths, the trap is often on show. Exposed shallow seal traps are available in metal finishes such as chrome, black and brushed brass, often with a matching outlet pipe that runs to the wall or floor. Choosing the same finish as your taps and bath feet makes the trap part of the design.
Keeping a Shallow Seal Trap Working
Because a shallow seal holds less water, it can be more sensitive to drying out if a bath is not used for a long time. Running the bath taps for a moment every so often keeps the seal topped up. If you notice a smell from the plughole after a period of non-use, this is often the cause.
- Clear hair from the plug regularly to prevent build-up in the trap.
- Check the joints for drips when you clean the bath panel area.
- Use the access point or removable parts to clean the trap if water drains slowly.
Size and Connections
Bath traps normally use a 1½" (40mm) connection. Check the outlet direction you need and the type of pipe you are connecting to before you buy. Some traps have a universal or multi-fit outlet that connects to plastic, copper or lead pipe.
Is a Shallow Seal Trap Right for You?
For most baths, yes. If your bath has very little space underneath, a shallow seal trap is usually the practical choice. If you have a freestanding bath, an exposed shallow seal trap gives a neat, matching finish.
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See our bath waste traps and the full waste and traps range. Our guide on how bath wastes and overflows work explains how the trap fits into the rest of the bath installation.