The J5515/J5514 on wheels are for driveways, walkways, asphalt, pavement, etc. J5510 is designed to hover (no wheels) for cleaning rough surfaces like rooftops or rock beds. Performance is largely dependent upon an industrial pressure washer with higher flow and pressures (up to 8GPM at 4000psi, depending on model). Periodically check the tips and swivels to ensure they are not clogged or rusted. Default unit comes with two part # T2502S2M spray tips for a 3GPM pump (two 25 deg 2.0), however they can be swapped out based on the washer machine ratings (keeping in mind # of nozzles vs GPM). 4GPM pump use two T25025S2M tips, 5GPM use T2503S2M tips, 6GPM use T25035S2M). During operation, should you experience a buildup of small stones or other foreign material within the cover, we recommend that you simply tip the cleaner on its side at 45 degrees, expel any foreign materials. This will give longer life to your tips, swivel arm, nozzles, and brush skirt. The tips that have been installed on your surface cleaning system permit the use of your cleaner with a pressure washer producing up to 7 GPM at 4000 PSI. Periodically check the tips to ensure they are not clogged by dirt or other matter as this can cause the rotary arm to stop spinning, leading to missed areas on the surface being cleaned. Ensure that the nylon brush skirt remains in contact with the surface being cleaned. Do not operate on overhead surfaces. We strongly recommend that safety goggles, gloves, and work boots be worn when operating a surface cleaner. Refer to our webstore for replacement parts (J5515Rxx-20) and operating/maintenance information.