*PLUMBERSSTOCK EXPERT* responded:
Hello there! Thank you for posting a question about the Generac 6598 Pressure Washer. To answer your question, you need to open the container cap (if so equipped). Depending on the model, insert the filter on the end of the siphoning tube through the hole in the loose cap (supplied). For more information, please refer to page 10 and 11 of this Operator's Manual. We hope this helps. Should you have further questions, don't hesitate to ask. PlumbersStock is happy to assist you. Have a great day!