[Paul]

Joe,

Rethink the need to use that type of valve.

You drain your air tanks for two reasons. The presence of water is a bad thing with the exception of a tablespoon or two out of the wet tank. You want to be able to note the amount of water and with the location of the tanks up high and out of sight except when beneath the coach it is going to be difficult to detect moisture.

But the draining of the tanks if done in sequence provides a verification the protection and check valves are functioning. If you use lanyards you have to be sure to be patient, drain each tank in succession and try to judge if each has held pressure. You can do that by draining the first, looking at the gauges, then the second, look at the gauges, etc.