When water is pumped by an engine and stored for use in a tank to be delivered under pressure in the house, then the additional cost of hot and cold water and the necessary sink and bath room fixtures is comparatively small. Modern plumbing fixtures fit so perfectly and go together so easily that the cost of installing house plumbing in the country has been materially reduced, while the dangers from noxious gases have been entirely eliminated. Open ventilator pipes carry the poisonous gases up through the roof of the house to float harmlessly away in the atmosphere. Septic tanks take care of the sewerage better than the sewer systems in some towns. Plumbing fixtures may be cheap or expensive, according to the wishes and pocketbook of the owner. The cheaper grades are just as useful, but there are expensive outfits that are very much more ornamental.

FARM SEPTIC TANK

Supplying water under pressure in the farmhouse demands a septic tank to get rid of the waste. A septic tank is a scientific receptacle to take the poison out of sewerage. It is a simple affair consisting of two underground compartments, made water-tight, with a sewer pipe to lead the waste water from the house into the first compartment and a drain to carry the denatured sewerage away from the second compartment. The first compartment is open to the atmosphere, through a ventilator, but the second compartment is made as nearly air-tight as possible. The scientific working of a septic tank depends upon the destructive work of two kinds of microscopic life known as aerobic and anaerobic forms of bacteria. Sewerage in the first tank is worked over by aerobic bacteria, the kind that require a small amount of oxygen in order to live and carry on their work. The second compartment is inhabited by anaerobic bacteria, or forms of microscopic life that work practically without air. The principles of construction require that a septic tank shall be large enough to contain two days’ supply of sewerage in each compartment; thus, requiring four days for the sewerage to enter and leave the tank.

Estimating 75 gallons daily of sewerage for each inhabitant of the house and four persons to a family, the septic tank should be large enough to hold 600 gallons, three hundred gallons in each compartment, which would require a tank about four feet in width and six feet in length and four feet in depth. These figures embrace more cubic feet of tank than necessary to meet the foregoing requirements. It is a good plan to leave a margin of safety.

It is usual to lay a vitrified sewer, four inches in diameter, from below the bottom of the cellar to the septic tank, giving it a fall of one-eighth inch in ten feet. The sewer enters the tank at the top of the standing liquid and delivers the fresh sewerage from the house through an elbow and a leg of pipe that reaches to within about six inches of the bottom of the tank. The reason for this is to admit fresh sewerage without disturbing the scum on the surface of the liquid in the tank. The scum is a protection for the bacteria. It helps them to carry on their work of destruction. The same principle applies to the second compartment. The liquid from the first compartment is carried over into the second compartment by means of a bent pipe in the form of a siphon which fills up gradually and empties automatically when the liquid in the first compartment rises to a certain level. The discharging siphon leg should be the shortest. The liquid from the second compartment is discharged into the drain in the same manner. There are special valves made for the final discharge, but they are not necessary. The bottom of the tank is dug deep enough to hold sewerage from two to four feet in depth. The top surface of the liquid in the tank is held down to a level of at least six inches below the bottom of the cellar. So there is no possible chance of the house sewer filling and backing up towards the house. Usually the vitrified sewer pipe is four inches in diameter, the septic tank siphons for a small tank are three inches in diameter and the final discharge pipe is three inches in diameter, with a rapid fall for the first ten feet after leaving the tank.

Septic tanks should be made of concrete, waterproofed on the inside to prevent the possibility of seepage. Septic tank tops are made of reinforced concrete with manhole openings. Also the manhole covers are made of reinforced concrete, either beveled to fit the openings or made considerably larger than the opening, so that they sit down flat on the top surface of the tank. These covers are always deep enough down in the ground so that when covered over the earth holds them in place.

In laying vitrified sewer it is absolutely necessary to calk each joint with okum or lead, or okum reinforced with cement. It is almost impossible to make a joint tight with cement alone, although it can be done by an expert. Each length of the sewer-pipe should be given a uniform grade. The vitrified sewer is trapped outside of the building with an ordinary S-trap ventilated, which leaves the sewer open to the atmosphere and prevents the possibility of back-pressure that might drive the poisonous gases from the decomposing sewerage through the sewer back into the house. In this way, the septic tank is made entirely separate from the house plumbing, except that the two systems are connected at this outside trap.

It is sometimes recommended that the waste water from the second compartment shall be distributed through a series of drains made with three-inch or four-inch drain tile and that the outlet of this set of drains shall empty into or connect with a regularly organized field drainage system. Generally speaking, the final discharge of liquid from a septic tank that is properly constructed is inoffensive and harmless. However, it is better to use every possible precaution to preserve the health of the family, and it is better to dispose of the final waste in such a way as to prevent any farm animal from drinking it.

While manholes are built into septic tanks for the purpose of examination, in practice they are seldom required. If the tanks are properly built and rightly proportioned to the sewerage requirements they will take care of the waste water from the house year after year without attention. Should any accidents occur, they are more likely to be caused by a leakage in the vitrified sewer than from any other cause. Manufacturers of plumbing supplies furnish the siphons together with instructions for placing them properly in the concrete walls. Some firms supply advertising matter from which to work out the actual size and proportions of the different compartments and all connections. The making of a septic tank is simple when the principle is once understood.

INDEX