The smaller the filter particle size the quicker the filter will clog. You really only need maybe a 20 mesh screen first. If it is a CSV125 even small particles will cause it to leak, as it is made for clean water applications. But the CSV1A is designed to handle some debris, and it is probably best to filter after the CSV1A. Placing the filter before the CSV it will see more pressure than if after the CSV. You need to know the back pressure of your pump to make sure the filter before the CSV is rated for enough pressure.