1. The furnace and the water heater should be placed in the basement. If you new home is not going to have a basement, the second best place for the hot water heater and furnace is on the main floor of the home. Be sure to have the water heating unit installed with an aluminum drain pan underneath the unit. Secondly, be sure that the drain pan is connected to the sewer.
2. If there is a basement, be sure to have your water softener, water heat, sump pumps, etc. all in the same corner/location of the basement.
3. Have a water main shut-off valve plumbed into the main living space of the home if you are building onto a crawl space foundation. The last thing you want if there is a water emergency is to have to try to get into the crawl space to shut off the water supply to the home.
4. Have the house plumbed for a water softener. Even if you don’t install one, having the house plumbed for one can be a great way to allow for one to be installed later; not to mention it could be a nice selling point should you decide to re-sell at some point.
5. If you new home will have a sump pump, make sure that the discharge line is plumbed to empty away from the home (or into the storm sewer).