What is continuous venting?

Several examples of continuous venting are shown in illustration on page 123. It consists, as shown in No. 1, of connecting the outlet from the trap directly into a vertical fitting, the bottom of the fitting serving as a waste, and the top serving for the vent connection. Nos. 2, 3 and 4 show other examples of this method. In the case of the water closet, continuous venting is obtained by continuing the branch soil pipe, full size, beyond the line of water closets and upward through the roof or into a line of vent. Through this line the water closet traps are supplied with air, and it is claimed that the results are as satisfactory as when each water closet is separately vented.

What is the advantage of continuous venting?

There is far less danger of such a vent connection becoming fouled with grease, etc., and finally closing up. The supply of air is brought in less directly upon the trap seal, and consequently the rate of evaporation is lessened. In many instances continuous venting results in a saving of expense both in material and labor.

What kind of fittings are generally used on the connection for a continuous vent for other fixtures than water closets?

Fittings of the T - Y style are generally used for this purpose.

Why may not Y branches be used for this purpose?

On most work the Y branch would bring the vent connection too low to properly guard the trap against syphonage.

In what special way may the continuous vent principle be applied to a stack which serves fixtures on two floors only?

When the fixtures are conveniently located, as on opposite sides of a partition, the plan shown in illustration No. 3, on page 123 may be followed with a considerable saving in expense.

Why could not this plan be followed if waste from more than two floors entered the stack?

For the reason that the waste from the third floor would necessarily have to enter a pipe which served as a vent for one of the other floors.

What are the relative advantages of different methods of venting S traps?

Referring to illustration on page 105 we give four methods of venting.

That which is most acceptable is No. 4, which illustrates the continuous vent, of which we have just spoken, naming its advantages.

No. 1 shows the vent taken off the crown of the trap. This method causes direct contact of the air supply with the seal, causing evaporation at its highest rate. The vent connection is almost certain to fill up eventually as is that of No. 2 also. No. 2 has the advantage of bringing the air in less direct contact with the seal however. In the case of half-S and 3/4-S traps, the vent may often be placed at a considerable distance from the seal and still protect the trap, and with less danger of stoppage of the vent opening. In order to ensure a good supply of air, however, it should not be placed at a level lower than that of the trap seal.