I'm trying to innovate a problem that I got myself into. The problem is we have four full baths in a house that originally had one full bath. The plumbing is pretty new, including a brand new line right to the house, It's 1 inch and then immediately reduced to 3/4 inches. Problems really started happening after the water line replacement but I have checked the pressure and it is 60 psi wherever I check it if no water is running. If one shower is on, it immediately drops to 20 or lower. If I am filling the jacuzzi bath, the shower and sink upstairs actually begin sucking in air. So I'm assuming I have a "flow" problem and not a "pressure" problem. It seems I need a larger pipe diameter leading to each bath to increase flow. But even that might not be enough. And that would be too much work especially considering that it's all new pipe. I'm considering a gravity option for the baths on the second floor. We have a large attic that could have a tank, and to connect to baths would be easy. (we have a tall, narrow row house. I'm also thinking about solar hot water collectors on the roof (long flat roof facing south) and feeding them right to the water tank in the attic. But will it correct the pressure/flow problem? Do I need to pump the water up the tanks in the attic or can it just trickle in until it's full. Will gravity provide enough pressure or do I need a pressure tank and pump to fill it? Grateful for any advice.