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 PAGE