There is no honest one-number answer for Tucson air filters. “Every 30 days” can waste a perfectly usable filter in one house and leave another house choking on dust. Check the filter monthly at first, then set the replacement interval from what you actually see.
Why two neighboring homes can be different
A house with two shedding dogs, nearby construction and a basic one-inch filter will load faster than a lightly occupied home with a larger media cabinet. Summer runtime, open doors, remodeling and monsoon dust all shorten the interval. Filter thickness and the system’s airflow capacity matter too.
Pull the filter and look across the pleats in good light. A gray surface is not automatically finished. Replace it when dust is packed into the material, airflow has clearly dropped, the filter is damp or damaged, or it no longer fits tightly in the rack.
Do not shop by the highest MERV number
A more restrictive filter may capture smaller particles, but the blower still has to move enough air through it. Installing the “best” filter on the shelf can create poor airflow if the return and filter rack were not designed for it. Use the size printed on the existing filter and ask a technician before making a large jump in rating or thickness.
Clues that the problem is bigger than the filter
Replace a visibly dirty filter, but do not assume it explains ice on the refrigerant line, water around the indoor unit or a system that still has weak airflow. Those symptoms can involve the blower, coil, ductwork or refrigeration circuit. Let frozen equipment thaw with cooling off and arrange diagnosis rather than scraping the ice.
Write the filter size on the equipment or save a photo in your phone. It is a small step that prevents a surprising number of wrong purchases.
Sonoran can verify filter fit and airflow during AC maintenance. Call 520-303-3220 or schedule service.