There are three things which will affect the plumbing system of the small house; namely, the existence or non-existence of municipal plumbing codes under which the structure is erected, the existence or non-existence of a public sewer, and, finally, the type of water-supply, whether it is public or private.
If there are no plumbing codes to follow, it is sometimes possible to save money on the plumbing; but unless the specifications are very rigid, there is danger of poor work being installed. By saving money is not meant installing cheap material, but eliminating certain features which most plumbing codes require and which are not essential in producing the best possible type of plumbing system. For example, in most cities the ordinary traps which are required under each fixture to prevent the sewer-gas from returning into the air of the house, after the waste water has drained out, must be equipped with back-vent pipes in order to eliminate dangers of siphonage. The cheap S trap (shaped like an S turned on its side) without this back-venting will siphon out, that is, lose its water-seal by atmospheric pressure pushing the water out of the trap in its attempt to fill a vacuum created by the discharge from a water-closet on the floor above. By back-venting these traps, as shown on page 94, this danger of siphonage is reduced, and, therefore, most codes have adopted this regulation requiring back-venting. But to-day the market offers certain traps which are claimed to be anti-siphonable and which do not require this back-venting, with the consequent result of reducing the cost of the equipment. Most plumbing codes have not changed their old regulations, for many authorities do not yet believe in the possibility of an anti-siphon trap, and so require the use of the back-venting system. Consequently, wherever the small house is constructed within jurisdiction of these laws, the plumbing will cost more than where the anti-siphon trap can be used without the elaborate system of back-venting.
Likewise, wherever there is a public sewer, the problem of sewage disposal is simple and cheap; but if the house is not located near any such public convenience, special methods must be employed for the destruction of the waste matter. The best is the septic tank (see illustration) with the small subsurface irrigation tile, through which the partially purified material from the septic tank is distributed under the ground for complete purification by air and bacteria. The other method of disposal - pouring the sewage into a cesspool - is to be deplored, unless there is possibility of an early construction of a public sewer, and no drinking-water is secured from the premises.
The third consideration which affects the plumbing system of the small house is whether it can draw upon a public water-supply, or whether it must secure its private supply from a well or a near-by stream or lake. A private source of supply generally means the erection of a storage tank. The best type of tank for this purpose is the pneumatic tank, which is installed in the cellar, and not in the attic, as was the old-fashioned tank. The water is pumped into this tank, and the air which is in it is trapped, so that the more water that is pumped into the tank, the more compressed becomes the air. This springlike cushion of air gives enough pressure to force the water to any fixture in the house.
SMALL SEWAGE. DISPOSAL. PLANT.