Clean only the owner-serviceable air filter identified in your heat pump water heater's manual. Remove it as directed, wash or replace it according to the filter type, and reinstall it completely dry if it is washable. A filter reminder does not by itself prove the compressor has failed.
Identify the filter before cleaning it
Some filters are washable. Others need replacement, and an appliance without an owner-removable filter needs different service. ENERGY STAR describes air-filter maintenance as a possible requirement for heat pump water heaters and directs owners to the manufacturer's instructions. That does not establish one cleaning method or calendar interval for every heater.
The cited Rheem hybrid manual shows a removable filter at the top. Its routine-care section permits mild detergent and water, followed by drying and reinstalling the filter. Its T131 reminder instructions say to select Electric or Off before cleaning and restore the desired operating mode afterward. Use that sequence only when it applies to your heater and manual revision.
Clean it without disturbing the heat pump
Make sure you can reach the filter from a stable position. A shelf or low ceiling that blocks removal is an access problem; do not take apart the top housing to get around it. Follow the model's operating and power precautions, remove the filter along its intended path, and inspect it for damage.
For a washable filter, rinse out the dust using the approved method. Let it dry completely before fitting it back into its slot. Do not add an extra layer of filter material or leave the heater running with its required filter missing. Follow the manual for clearing a reminder; resetting the display alone does not clean anything.
What if the reminder returns or hot water is still limited?
Check that the filter is seated and that the heater's air openings are clear. A clean filter does not correct an undersized tank, restricted room airflow or another alarm. Record any separate error code and the operating mode before requesting service. Leave fan, wiring, sensor and compressor testing to qualified service personnel.
If the heater is in a closet, also compare the installed model's airflow and ducting arrangement. Cleaning the filter does not establish that the room or duct route provides the required air.
Our guide to what a hybrid water heater is explains its air and installation needs. For tank care beyond the filter, see getting the most life from a water heater. If recovery remains poor, choosing a water heater size helps separate capacity from maintenance.