Posted By Old Boy on 02/14/2009 4:48 PM
A "bypass" valve is just an on-off valve, nothing more than that, and it can be either a quick on-off, like a ball cock, or a conventional stem valve. What happens is the pump works all the time and the pumped water is piped so as to be able to go one of two ways, . . . to the clack valve and into the boiler, or return to the tender tank. Given the choice of whether to try to overcome boiler pressure and pass through the clack, or return unobstructed to the tender, the water will always take the path of least resistance and return to the tender, unless you obstruct its path to the tender with a valve (the by-pass valve.) Then the path of least resistance is through the clack and into the boiler. So a by-pass valve is simply on-off, or anything that will shut down the water return path to the tender.
Yep, Like this:
