How does the expansion of water differ from that of other substances?

As previously stated, substances in general continue to expand as long as heat is added, and to contract as long as the heat applied grows less. Water is heaviest at a temperature of 39.2 degrees, and when heated above or cooled below this point, it expands. If this were not so, at the freezing point, the coldest water would be at the bottom, and the formation of ice would begin at the bottom of ponds and rivers, and the entire body of water would finally become a solid mass of ice.

Does heated air rise or fall, and why?

It rises, because it is lighter than cold air, that is, it is more expanded.

In what way is this fact applied in plumbing?

Local vents from water closets are entered into heated flues, in order that the warm air rising in the chimney may create a draught or suction which will draw out through the vent and into the chimney, the foul odors of the water closet. It applies in ventilation also.

Is hot water lighter or heavier than cold water, and why?

It is lighter, because when heated it is more expanded.

In what way is this fact applied in plumbing?

The heated water being lighter than the cold, naturally rises. This gives us the fundamental principle of all circulation work.

What is a vacuum?

A vacuum is a portion of space from which the air has been entirely exhausted.

How may a vacuum be formed in plumbing work?

A stoppage in the waste of a fixture may cause the waste to back up and fill the pipe. When it runs out it may go with a sufficient rapidity to exhaust the air and produce a partial vacuum in the waste, resulting in syphonage. One or more fixtures may throw enough waste suddenly into a waste pipe to nearly fill it, and as this volume of water flows by a branch waste pipe serving another fixture, the air in that branch may be exhausted, forming a partial vacuum. In fact, in every case where syphonage of traps occurs, or the syphonage of boilers, a vacuum must have been formed, and usually in some such manner as we have just shown.

What is evaporation?

It is the slow passage of a liquid into the form of vapor.

What causes increase evaporation?

Increase of temperature, increased exposure of surface, and wind blowing over the surface.

In what way is the effect of evaporation felt on the plumbing system?

In the evaporation of trap seals.

How does the ventilating system affect the evaporation of trap seals?

It increases it, by bringing in air upon the seals.

How does the fresh air inlet affect the evaporation of the seal of the main trap?

It increases it, by bringing in air upon the seal.

Which is more affected by evaporation, the drum trap or the S trap?

The drum trap is affected to a less dangerous degree, for its seal is usually greater, and, in addition, the vent taken from the drum trap usually brings in the air upon the seal in a less direct manner.