Current building regulations state the minimum depth seal for traps should not be less than 38mm. However, 19mm water seal traps have been manufactured to meet the demand for replacement traps where the original shallow seal traps were installed prior to the current regulations. It is not uncommon in older properties for the waste from baths or showers to have shallow seal traps and discharge into an open hopper head. New 19mm water seal traps are often used when replacing the sanitaryware in these properties. This practice does not comply with current building regulations and they could be rejected if the installation comes under the scrutiny of the local authority building control officer.