What is a trap?

A trap, as applied to plumbing, is a vessel containing a body of water, the purpose of which is to prevent the passage of sewer gas and foul odors from the sewer or cesspool into the house.

What is the purpose of the house or main trap?

To prevent the entrance of gases from the sewer into the drainage system of the house.

What is the use of the trap under each fixture?

To prevent the entrance through the fixtures of gases and odors that form between the fixtures and main trap, or, if there is no main trap, to prevent such entrance directly from the sewer or cesspool.

What is meant by the trap seal?

The depth of water between the outlet of the trap and the dip.

What is ordinarily a safe depth of seal?

From 1 to 2 inch.

Name different ways in which trap seals may be broken

By syphonage, evaporation, capillary attraction, back pressure, and momentum, that is by the action of the waste itself as it passes off with considerable force. The trap seal may also be broken by being blown out by gusts of wind. The latter action may occur gradually, a few drops being blown out at a time.

What qualities should a trap possess?

It should have a good seal, be non-syphonable, self-scouring, have no internal partitions, depend on no mechanical device, and have as few corners or places where filth may collect as possible.

Why are traps with internal partitions dangerous?

A flaw may exist in this partition above the water line through which gas may enter the house.

Why are traps having mechanical seals now prohibited in most cities?

The mechanical parts give opportunity for the collection of grease and foreign matter in the trap and the mechanical seal is soon rendered imperfect.

What are the two principal types of traps on which all other traps are based?

The S trap and the drum trap.

What are the comparative advantages of the S and drum traps?

The S trap, being self-scouring, is cleaner than the drum trap, but when unvented, the drum trap is much less liable to syphonage. The drum trap may often be used to better advantage under the floor than the S trap.

Is it the amount of water in the trap or the depth of seal that offers the most resistance to syphonage?

It is the amount of water.

Is it the amount of water in the trap or the depth of seal that offers the most resistance to sewer gas?

The depth of seal offers the greatest resistance.

What is the effect of the pressure of sewer gas on the trap seal?

It saturates the water in the trap with sewer gas, which is finally thrown off into the room.

How is the pressure of sewer gas upon the trap seal prevented?

By back venting the trap.

What precautions should be taken with traps in unoccupied houses during the cold months?

If the traps are of iron or lead, they may be salted, but if of earthen ware, after the water has been taken out, parafine oil should be used for a seal.