If your house was built before World War II, the plumbing may be a fairly recent feature. If it was built before the turn of the century, indoor plumbing may not even have been a gleam in a contractor's eye.
Baltimore didn't have a comprehensive municipal sewage system until 1911, making it the last of the major East Coast cities to have such an amenity, according to Dean Krimmel, curator of local history for the Baltimore City Life Museums.
By 1850, "houses of the elite" had cold water indoors, Mr. Krimmel says. After the Civil War, larger houses, like the 'N three-story Italianate "mansions" common to many of the city's neighborhoods, had cold water indoors and some kind of drainage system, to a cesspool or privy.
"Bathrooms didn't become common until 1915 in two-story, working-class houses," Mr. Krimmel says.
That explains why a lot of Baltimore houses have "afterthought" plumbing, with drainpipes running up the outside of the back wall. Kitchen and bathrooms were stacked at the back of the structure, sometimes in an addition.
The house we're working on is a classic in this sense: Though the main part of the house is about 120 years old, the plumbing was almost entirely confined to a 5-foot deep, three-story addition built sometime around World War II. There was one odd, added-on bath perched at the top of the third-floor stairs, with a water heater tucked into a nearby bedroom.
We believe the original mansion was converted to a sort of boarding house around the time of the war, when workers were pouring into the city to man the steel mills, shipyards, aviation factories and canning plants.
After the war, government policy encouraged young families to decamp to the suburbs. No one wanted the big old mansions; many, many once-elegant properties became multifamily dwellings. As systems wore out and newer, inexpensive housing became available, many of the old houses simply were abandoned.
When we bought our current old house a couple of years ago, it still had its back-of-the-house plumbing. (From the quality of the work, we'd say our house was converted in a couple of weekends by some guys with too few tools for their own good.)
But installing plumbing suitable to meet the 21st century isn't a simple matter. Behind the visible fixtures, plumbing has three hidden parts: water lines, drains and vents. The water lines are independent, but both the drains and vents connect to the main drain pipe, or stack.
Because of the way the house was built, we are stuck with stacking the spaces that need plumbing: Bath on the ground floor, kitchen and powder room on the first floor, master bath on the second floor. All the walls will be framed out. Where the drain pipes will run, the framing is set out 2 inches from the wall to allow space for the 3- to 4-inch-wide drain pipes. The main stack, or drain pipe, will run inside the back wall; the kitchen sink vent will run up the side wall to a level 40 inches above the second floor, then rise slightly through the wall to connect with the stack.
The old cast-iron drain, which ran in the brick wall between our house and our neighbor's house, has to be replaced. It's going to mean digging up the main sewer connection, which is 4 feet below the concrete floor on the ground level, to connect a new pipe.
(By the way, it helps to know exactly where the sewer pipe enters the house before you begin laying out the plumbing. Its location will dictate how much flexibility you'll have in installing plumbing in the lowest level. If the main sewer line leaves the house in the middle of the basement wall, you may not be able to have a basement bath, or even a basement laundry room. If there's no place else for the laundry, you can install an ejector pump under a laundry sink that will force water up into the drain.)
The problems with the back plumbing pale, however, compared with the problems of installing a family bath and laundry area on the second floor in front of the stairs.
There's plenty of room; the problems again are with running the drain pipes and vents, and they're all on the first floor, below the bath/laundry area. The drain pipes have to run between the joists; building codes don't allow chopping holes for them. Drain pipes and water pipes have to slant down a quarter-inch for every linear foot; vents have to slant up a quarter inch for every linear foot. Since some of the fixture connections are already below the floor (for instance, the bathtub trap), even a 10-inch joist may not be deep enough to enclose the pipes.
The space for the pipes has to come out of the ceiling space below. In our case, the room below is the living room, the only room in the house that still had some original trim.
While we were still agonizing over sacrificing the plaster ceiling molding and some space next to the fireplace (for a drain, plus new flue for the furnace and new cold-air return for air-conditioning), the molding solved our problem by letting go in chunks and crashing to the floor.