Pressure-activated trap primer valve

Abstract

A pressure activated trap primer valve for drain traps includes an expansion chamber with a piston between the compressible air and water. The piston prevents waterlogging of the expansion chamber to reduce maintenance of the trap primer valve. The trap primer valve also includes an inlet pipe coaxially configured in the expansion chamber. The inlet pipe is operably connected to a chamber below the expansion chamber which is closed at the bottom by a diaphragm. The diaphragm in a relaxed, undeflected position closes an outlet that drains to the trap. A chamber below the diaphragm is replenished by the expansion chamber. When pressure in the supply pipe and inlet pipe decreases, such as when a faucet is opened, the diaphragm deflects. Deflecting the diaphragm opens the outlet, allowing a limited amount of water to flow out of the chamber and into the trap. The intermittent water flow to the trap ensures a minimum volume for maintaining a gas tight seal in the trap. As trap primer valve pressures reach equilibrium, the diaphragm returns to an undeflected position, sealing the outlet again.

1 . A trap primer comprising
 a first section separated into an upper air chamber and a lower water chamber by a sliding piston configured to prevent air leaving the upper air chamber;   a second section, below the first section, the second section divided into an upper chamber and a lower chamber by a diaphragm;   an inflow pipe through the center of the first section to the upper chamber of the second section; and   an outlet from the second section lower chamber with flow from the outlet controlled by the diaphragm;   wherein the upper chamber of the second section is connected to the first section by a check valve;   the lower chamber of the second section is supplied with water from the first section; and   a drop in pressure at the inflow pipe raises the diaphragm, releasing water from the outlet.   
   
   
       2 . The trap primer of  claim 1  where the sliding piston is sealed at inner and outer circumferences by o-rings. 
   
   
       3 . The trap primer of  claim 1  where the check valve has a ball and a seat. 
   
   
       4 . An expansion chamber to be used in a trap primer valve, the expansion chamber comprising:
 a first inner coaxial tube configured to connect to a water supply line;   a second outer coaxial tube which acts as a housing;   a first, upper end of the expansion chamber, the upper end closed by joining the inner and outer tube;   a second, lower end of the expansion chamber defined by a piston slidable between the inner and outer tube;   wherein the expansion chamber is charged with a gas that acts on a first upper side of the piston;   water pressure in the supply line acts on a second lower side of the piston;   the piston is sealed to the inner and outer coaxial tubes; and   displacing the piston changes the volume of the gas in the expansion chamber.   
   
   
       5 . The expansion chamber of  claim 4  where the piston is sealed by o-rings at the inner and outer circumferences of the piston. 
   
   
       6 . The expansion chamber of  claim 4  where the expansion chamber is part of a primer valve that operates as a function of changes in line pressure. 
   
   
       7 . The expansion chamber of  claim 4  where the first and second coaxial tubes are composed of copper or copper alloy. 
   
   
       8 . The expansion chamber of  claim 4  where the piston is composed of polyvinylchloride. 
   
   
       9 . A piston to be used in a closed expansion chamber including a water supply pipe comprising;
 an annular disk with a first inner circumference and a second outer circumference;   a seal located at the first circumference that contacts the supply pipe; and   a seal located at the second circumference that contacts an expansion chamber wall;   wherein the piston divides the expansion chamber into a closed upper gas filled section and a lower water filled section; and   differences in pressure between the upper filled gas section and the lower water filled section displaces the piston.   
   
   
       10 . The piston of  claim 9  where the seals are o-rings. 
   
   
       11 . The piston of  claim 9  where the annular disk is formed from polyvinylchloride.