From the Teknos manual for its hydrochloric acid product:
Dilute the hydrochloric acid to 5% (5 liters of water + 1 liter of technical hydrochloric acid 30% in a plastic bucket). Water with a spout can, 0.5 liters per square meter. Let it act for 5 minutes (foams heavily when carbonic acid is released) and then scrape the salt solution that forms into the floor drain. If there is no floor drain, collect it with a shovel and rubber spatula. Rinse with water.
Protect eyes with goggles and wear full-covering cotton clothing and rubber boots.