"drain valve" is correct and usable in written English.
You could use it in a sentence like, "The plumber used a wrench to open the drain valve."
First turn off the burner and close the inlet valve; then position a bucket under the drain valve.
After draining the boiler, close the drain valve, open the inlet valve and turn the burner back on.
In its raw form, though, "it doesn't smell so good," said Mr. Lynn as he opened a drain valve at the bottom of his mixing container to allow the black liquid to ooze into a bucket.
Hundreds of tanks have been built at the site to store contaminated water that is being fed into reactor buildings to cool melted fuel rods, as well as underground water running into reactor and turbine basements.Tepco suspects that the water may have leaked through a drain valve connected to a gutter around the tank, which is located about 500 metres from the shore.
In a case, hydrochloric acid was stored in a polyester tank that was fitted with a drain valve near the base.
There were three water level cocks on the left side, near the water pump, and a drain valve on the bottom.
The feed and drain valves (2, 3) are repeated for each additional tube array to accommodate a series of parallel reactors which operate separately.
Operators had no idea the drain valves were open.
Open the manual drain valves.
Close the manual drain valves after draining the water.
Check the door latch, float assembly, inlet and drain valves.
