A backwater valve has a valve body, and a valve member pivotally movable about a pivot axis between an open position away from the valve body and a closed position covering the valve body. A control linkage is provided with at least one of a float or a counterweight in communication with the valve member via the control linkage to modify operation of the valve member.

There is provided a powerless back-flow prevention apparatus comprising: a body having a sewage inlet at a front thereof, a sewage outlet at a rear thereof, and a length-wise sewage channel there between; a door pivotally coupled to the body at the rear thereof to open or close the outlet, wherein the door comprises: a number of floating members arranged spacedly with each other; and a guide disposed on the floating members to pivot upwards via the floating force to close the outlet, and to pivot downwards via a gravity in an absence of the sewage back-flow to open the outlet, and, then to guide the sewage from the outlet.

A backflow prevention device including a tank having a holding chamber and first and second inlets connected with the holding chamber; a control valve having an intake chamber and first and second discharge chambers connected with the first and second inlets, respectively, the intake chamber connected with the first discharge chamber through a valve inlet; a valve sealing element for opening and closing the valve inlet, the second discharge chamber connected with the intake chamber through a hole of the valve sealing element; a float in the holding chamber; a slide bar in the holding chamber, contacting the float, and moveable toward the second inlet under the action of the float; and a slide bar sealing element for controlling opening and closing of the second inlet. When the second inlet is closed, the valve inlet is closed; and when the second inlet is open, the valve inlet is opened.

There is provided a liquid level control device (20) for location in a vessel to control the liquid level in the vessel. The liquid level control device (20) comprises: a first chamber (22) including: an opening (26) to allow movement of liquid between the first chamber (22) and the vessel; a vent (28) to allow egress of air from the first chamber (22); and an inlet (30) connectable to a liquid source (34); a first flow controller including a first float (36) arranged in the first chamber (22) such that the flow of liquid into the first chamber (22) raises the first float (36) and displaces air in the first chamber (22) via the vent (28), the first flow controller including a first closure member (40) movable to selectively close and open the inlet (30), the first float (36) further arranged in the first chamber (22) such that, in use, when the first float (36) is at a first position when the liquid level in the first chamber (22) is at or below a first predetermined level, the first float (36) positions the first closure member (40) to open the inlet (30) to allow liquid into the first chamber (22) via the inlet (30), and when the first float (36) is at a second position when the liquid level in the first chamber (22) is at or above a second predetermined level, the first float (36) positions the first closure member (40) to close the inlet (30) to block liquid from entering into the first chamber (22) via the inlet (30); and a second flow controller including a second float (42) and further including a second closure member (46) movable to selectively close and open the vent (28), the second float (42) arranged such that, in use, when the second float (42) is in a first position, the second float (42) positions the second closure member (46) to close the vent (28) to block air from flowing from the first chamber (22) via the vent (28) to escape to atmosphere, and when the second float (42) is in a second position, the second float (42) positions the second closure member (46) to open the vent (28) to allow air to flow from the first chamber (22) via the vent (28) to escape to atmosphere, wherein the first and second floats (42) are arranged such that, in use, when the first float (36) is in its second position and the second float (42) is in its first position, air is trapped in the first chamber

A backwater valve has a valve body, and a valve member pivotally movable about a pivot axis between an open position away from the valve body and a closed position covering the valve body. A control linkage is provided with at least one of a float or a counterweight in communication with the valve member via the control linkage to modify operation of the valve member.

A backwater valve has a valve body, and a valve member pivotally movable about a pivot axis between an open position away from the valve body and a closed position covering the valve body. A control linkage is provided with at least one of a float or a counterweight in communication with the valve member via the control linkage to modify operation of the valve member.

There is provided a powerless back-flow prevention apparatus comprising: a body having a sewage inlet at a front thereof, a sewage outlet at a rear thereof, and a length-wise sewage channel there between; a door pivotally coupled to the body at the rear thereof to open or close the outlet, wherein the door comprises: a number of floating members arranged spacedly with each other; and a guide disposed on the floating members to pivot upwards via the floating force to close the outlet, and to pivot downwards via a gravity in an absence of the sewage back-flow to open the outlet, and, then to guide the sewage from the outlet.

A backflow prevention device including a tank having a holding chamber and first and second inlets connected with the holding chamber; a control valve having an intake chamber and first and second discharge chambers connected with the first and second inlets, respectively, the intake chamber connected with the first discharge chamber through a valve inlet; a valve sealing element for opening and closing the valve inlet, the second discharge chamber connected with the intake chamber through a hole of the valve sealing element; a float in the holding chamber; a slide bar in the holding chamber, contacting the float, and moveable toward the second inlet under the action of the float; and a slide bar sealing element for controlling opening and closing of the second inlet. When the second inlet is closed, the valve inlet is closed; and when the second inlet is open, the valve inlet is opened.