Not sure how you are planning the renovation, but what I did was ground up, so I dug a big hole, and made a cement tank underground. The rainwater pipes will terminate in a course filter made of big rocks, smaller rocks and then fine sand, before reaching the tank. For the downspout, they have a bypass system (DIY) to make sure the first flush effect is in place before even reaching the underground tank. Rainwater pumped out will also be filtered by outdoor filter before being used. I use for watering, laundry and toilet flushing. So far so good.

I'm not going to clean the coarse (typo) filter since it's going to be dirt free due to the first-pass system in place before the rainwater ever reaches it. You need to PM me your WhatsApp then I can send you photos and discuss more if you want a DIY kind of rainwater catchment.