Check if the lifetime of the filter cartridge is exceeded and replace the cartridge if needed. In some cases, if the water filter is not used for a while, it is possible that certain sediments or contaminants can develop an unpleasant taste or odor in the system. Open the valves and let the water flow for at least 5 minutes. In rare cases, flushing the cartridge may not fully remove the unpleasant taste or smell, even though the cartridge is within its lifetime. This is generally caused by excessive sediment depositions in the cartridge, which can develop a bad taste or smell. Replace the filter cartridge. Please send a water sample to STIEBEL ELTRON, we will check if a point-of-entry (POE) pre-filter is needed to protect the water filter from excessive sediment deposits.