A valve that includes a housing defining first and second bores having a central axis, and a peripheral valve seat. An actuator is located in the first bore and has a reciprocating seal disposed for movement along the central axis for engaging the valve seat and closing the valve. A coiled return spring is mounted in the housing for urging the reciprocating seal towards the chamber to open the valve, the return spring having a first end connected to the reciprocating seal and a second end engaging a spring support in the housing facing the first bore. The return spring may have a larger diameter at its second end than its first end. The housing may include a third bore in communication with the second bore and having a different cross-sectional area than the second bore. A closure cap formed from moldable material may close an opening in the housing, the closure cap being sealably joined to the housing by a welded joint. The return spring could be supported by a discrete spring support located in one of the bores. The valve seat and an annular sealing member may have corresponding sloping surfaces that cooperate when the sealing member engages the valve seat.