“I have’t got around to this yet but I want to place a tank in my attic and connect it my domestic water system. Then the gravity will provide pressure to flush my toilets and use the sinks. I have the cold water to the kitchen sink isolated from the rest of the system now, so if I set up a filter system I could use the 55 gallon food grade drum I bought for drinking water and install it in the attic as well. The water tanks can be heated with solar, furnace or stove for washing or to prevent freezing in the winter.”
I advise against any tank in the attic. That is a huge amount of weight. Farmers/Ranchers have tanks that sit on steel legs about 15 feet in the air. These are normally used to hold gas and diesel for the equipment used. I suggest you think along that line and install them outside of the kitchen and bathroom. You can paint them or provide shelter from the sun over them depending on usage.