One of these main soil pipes might be dispensed with as shown in the simple plan.
Next there are the two rain-water stacks usual in city houses, either inside the house, to avoid freezing, or outside, one for the front and one for the rear.
These require here 85 feet of 4-inch extra-heavy pipe with 20 joints and 9 fittings, and cost, by the plumbers' estimates (taking in each case the average between the three figures submitted), $115.00.
Both of these pipes should be done away with where the the combined system of sewerage is used, because the 4-inch soil pipe stack is more than amply large enough to take care of all the rain from the roof, and because the combination of the rain with the soil pipe greatly improves the flushing.
We have next the 4-inch main drain pipe, with its 45 feet of extra heavy pipe, 21 joints and 9 fittings, costing $85.00.
Then come the branch waste pipes, which cost $65.00.
Next the two stacks of useless back-vent pipes with their branches having 180 feet of pipe of various sizes, 40 joints and 19 fittings, and costing $91.00.
Finally there is the main house trap and its fresh air inlet pipe, costing $30.00, a fair average for this foolish obstruction to ventilation and sewage outflow. It involves an average of at least 20 feet of 4-inch extra-heavy piping, a dozen joints, and half a dozen fittings including the trap itself. When the fresh air inlet pipe is carried up to the roof, as is often considered advisable for the purpose of carrying sewer gas away from the street level and up above the roof, on the same principle which directs that all soil and drain pipes shall discharge not less than 10 or 15 feet away from any window, then the cost of this item mounts up to double the figure we have given above as a fair average, but as the ordinances do not require this upward extension I have not included it.
The average allowance for testing, when the hydraulic and other tests for tightness are required by law, is put by plumbers at $25.00.
The hydraulic test is a very costly and entirely inexcusable extravagance, involving an undue strain on the lower end of the stacks and none at all at the top.
All the above items foot up to $615.00 for the sanitary drainage.
The fixtures shown in this plan are good but simple cast-iron enameled fixtures, and cost with their traps $290.00.
To this must be added a number of expansion joints in the main cast-iron stacks, to diminish fracture in piping and fixtures due to settlement or shrinkage of the building, where rigid joints are used, for which I think a moderate allowance would be $60.00. Adding these two items to the drainage cost we have a total of $965.00.
The cost of the cold and hot water supply and circulation pipes, including the copper boiler, is $254.00, making a grand total for all the plumbing and water supply of $1220.00.
In this plan the upper story bath room occupies the southwest corner of the house and has one window. As a rule both bath rooms are thus supplied with outer exposure on the mistaken idea that windows with sun exposure are essential in bath rooms for perfect sanitation.
Turning now to our one-pipe simpler plan in which all the bath rooms occupy the centre of the house, the southwest corner then becomes available for bed-chambers in which direct sunlight and outer air is without question essential for complete sanitation. The two extra bedrooms thus acquired when both the main bath rooms are moved from an outer exposure to the interior of the house, means a large increase of rental value.
The cost of the single, flexible-jointed soil pipe and its branches of "standard" thickness required under this one-pipe plan, is $51.00 by the plumbers' estimates as before, figuring in the same manner.
The drain pipe, also of "standard" thickness and flexible-jointed, figures out at $32.00. The testing of all the pipes in this system by a sensible, scientific smoke and low air pressure test, costs only $3.00.
The number of feet of piping in the entire one-pipe system of all sizes and "standard" weight amounts to only 115 against 475 feet of extra-heavy pipe in the two-pipe system, which is equivalent to 950 feet of standard pipe, so that the single system contains less than one-eighth as many pounds of cast-iron piping as the complicated system. The number of joints and fittings in the two systems is in similar proportion.
Assuming the same fixtures to be used in the two systems, the total cost of the sanitary drainage in the simple system, including the $68.00 for setting the fixtures, amounts to only $155.00, which is almost exactly one-quarter the cost of the corresponding work in the two-pipe system.
Adding to this the cost of the fixtures themselves, amounting as before to $290.00, we have a total for the whole sanitary plumbing in the one-pipe system of $445.00 against $963.00 in the other, which is less than half.
Add now for the water supply piping, as before $254.00, we have a total of $709.00 as against $1217.00, or a little more than half.
But from the saving of the outer bath room space for a bed-chamber or for two bed-chambers, where, as is usual, both bath rooms have outer exposures our $1217.00 must evidently be increased by the value of these two extra bedrooms.
The average value per cubic foot for houses of this class is estimated at between 25 and 30 cents. It was in this case found to be 30 cents. The bedrooms measure 10 feet by 12 feet, and are 10 feet high, giving a cubical contents of 1200 feet, which at 30 cents a cubic foot gives an increased sale value of $360.00 per room or $720.00 for the two. The loss of interior closet value due to placing these bath rooms in the centre of the house, is nearly offset by the space con-sumed and construction-cost of the three-story air-shaft and roof ventilating skylight required by the law for the lower water closets in the two-pipe system.