Anti-siphonic toilet

1. A wash-down toilet, comprising:

a bowl having a sump;

a passageway having an inlet, an outlet provided at a height above the inlet, and a weir, the inlet being in fluid communication with the sump;

a trapway having an inlet, an outlet, and a vent, the inlet of the trapway being in fluid communication with the outlet of the passageway, the outlet configured to be in fluid communication with a soil pipe; and

a supply of air provided from an air supply to the trapway by way of the vent;

wherein the vent introduces the supply of air into the trapway during a flush cycle to prevent siphoning; and

wherein the vent is configured as a one-way vent that prevents fluid from entering the vent from the trapway.

2. The wash-down toilet of claim 1 , wherein the trapway further includes an elbow disposed between the inlet and the outlet of the trapway.

3. The wash-down toilet of claim 2 , wherein the vent is provided on an upper portion of the elbow.

4. The wash-down toilet of claim 3 , wherein the vent provided on the upper portion of the elbow is located above a centerline of the inlet of the trapway.

5. The wash-down toilet of claim 1 , wherein the one-way vent includes a valve to prevent the fluid from entering the vent.

6. The wash-down toilet of claim 4 , wherein the vent has a cross-sectional size that is smaller than either a cross-sectional size of the inlet or a cross-sectional size of the outlet of the trapway.

7. The wash-down toilet of claim 6 , wherein the cross-sectional size of the vent is smaller than both the cross-sectional size of the inlet of the trapway and the cross-sectional size of the outlet of the trapway.

8. The wash-down toilet of claim 1 , wherein the inlet of the trapway is coupled to the outlet of the passageway through a set of mating threads.

9. A toilet configured to prevent siphoning during its flush cycle, comprising:

a bowl having a sump;

a passageway having an inlet in fluid communication with the sump, an outlet provided at a height above the inlet, and a weir provided at a height above the inlet between the inlet and outlet in the passageway;

a trapway having an inlet portion in fluid communication with the outlet of the passageway, an outlet portion configured to be in fluid communication with a soil pipe, and a vent tube positioned between the inlet portion and the outlet portion the vent tube configured as a one-way vent that prevents fluid from entering the vent tube from the trapway; and

a supply of air provided from an air supply to the trapway through the vent tube;

wherein the supply of air is fed to the trapway during a flush cycle to prevent siphoning; and

wherein the vent tube is provided above a centerline of a vertical cross-section of the inlet portion of the trapway.

10. The toilet of claim 9 , wherein the vent tube has a cross-sectional area that is smaller than a cross-sectional area of an inlet of the inlet portion of the trapway.

11. The toilet of claim 10 , wherein the cross-sectional area of the vent tube is smaller than a cross-sectional area of an outlet of the outlet portion of the trapway.

12. The toilet of claim 11 , wherein the cross-sectional area of the outlet of the outlet portion of the trapway is smaller than the cross-sectional area of the inlet of the inlet portion of the trapway.

13. The toilet of claim 9 , wherein the vent tube is cylindrically shaped including a centerline, wherein the vent tube extends between a first end coupled to the trapway and a second end, wherein the centerline of the vent tube at the first end is located between a centerline of the outlet portion of the trapway and the inlet of the inlet portion of the trapway.

14. The toilet of claim 9 , wherein a first end of the vent tube is coupled to a top side of an elbow portion interconnecting the inlet and outlet portions of the trapway.

15. A method for flushing a wash-down toilet, comprising:

introducing a supply of water into a bowl of the toilet to move water and waste in a sump of the bowl through a passageway to a trapway of the toilet, the passageway including an inlet and an outlet, wherein the outlet is provided at a height that is above the inlet and is in fluid communication with the trapway;

introducing a supply of air into the trapway through a vent to prevent a siphon when the water and waste flow through the trapway;

passing the water, waste, and air from the trapway; and

providing a remaining volume of water in the sump.

16. The method of claim 15 , wherein the vent of the trapway is provided above a centerline of a vertical cross-section of an inlet of the trapway, and wherein the vent tube has a cross-sectional area that is smaller than a cross-sectional area of the inlet of the trapway and a cross-sectional area of an outlet of the trapway.

17. The method of claim 16 , wherein the outlet of the trapway is fluidly connected to a first pipe and the vent is fluidly connected to a second pipe.

18. The method of claim 15 , wherein the vent is a two-way vent, such that gases are allowed to pass through the trapway and exit the vent into the second pipe, and wherein the water, waste, and air enter the first pipe through the outlet of the trapway.

19. The method of claim 18 , wherein gases are not passed through the second pipe while the water, waste, and air are passing from the trapway.

20. The method of claim 15 , wherein the vent is a one-way vent, such that the supply of air passes from the vent to the trapway, but gases do not pass from the trapway through the vent.

21. The method of claim 15 , further comprising preventing gases from passing from the trapway through the vent.