If there is a city supply of water, the small house should have a main supply-line from the water-main in the street of at least 3/4-inch diameter, but this does not give the service that a larger pipe, say a 1 1/4-inch pipe, does, for often with the smaller pipe, if the water is being drawn in the kitchen, none will be secured from the faucets in the second-floor bathroom. The kitchen-sink should have a service pipe of at least 3/4 inch, the tubs the same, and the lavatory 1/2 inch.

All service-lines should be compact and as direct as possible, and long horizontal runs under floors should be avoided. Hot-water supply-lines should be kept at least 6 inches from cold-water lines. There should be a shut-off at the entrance of the supply-line to the house, at the base of all vertical risers, and under each fixture. To avoid water hammer, it is best to take all faucets off the sides of the termination of pipes, rather than from the ends, for in this way an air-cushion can form, relieving the pounding action of the water in the pipes.

Supply-lines should never be run in the corners of buildings where they are in danger of freezing, and they should be kept out of the exterior walls of houses as much as possible for the same reasons. The packing of pipes where they pass through the floors will often prevent freezing caused by cold drafts around them.