I’ve seen how to clean a DE filter with back washing but that isn’t an option on my filter. How do I go about cleaning it? How much DE do a add after cleaning it? Manual said to add 6 lbs on start up. Also when do I clean it pressure wise? It started at 10 psi and is now close to 18 psi. Manual says not to run over 50 psi. It’s a new to me filter