Consider running the tank as a non-pressurized system rather than pressurized. You'll probably need a float switch to the valve (like a toilet tank) that lets water into the tank so it doesn't overflow. Then a pump to get it into the house. Using the domestic supply as a direct line into the house won't work if the domestic system goes down. It will be without pressure so won't "push" the water into your home.

You'll also need some system in place like a double check valve to ensure you don't siphon back into the domestic system should it lose pressure. Otherwise there goes all your water. Additionally, you'll face fines if you hook it up the way you're looking at: static systems like that can't be hooked to a domestic system or they risk contamination from stagnant water flowing back into their system. Hence the double check valve to eliminate backflow.