The answer to 'grout dusty' is that dusty grout is a common issue caused by a buildup of dirt, debris, and grime. This can happen over time as the grout pores become clogged, allowing dust and particles to accumulate. Symptoms include a dull, discolored appearance and a rough, uneven texture to the grout.
The good news is that dusty grout can often be cleaned and restored with some simple DIY methods. Start by sweeping or vacuuming the grout to remove any loose dirt and debris. Then use a grout brush or old toothbrush and a mild detergent or grout cleaner to scrub the grout lines. For tougher stains, you may need to use a grout haze remover or a diluted bleach solution. Be sure to rinse the area thoroughly afterwards. If the grout is severely damaged or discolored, you may need to regrout the entire area, which is best left to a professional tile and grout cleaning service.