can you use a pressure release valve as a drain?

Main Train Horns
1

my work truck uses what i can presume is a pressure safety valve as a drain eg on bottom of tank.

is this a good idea? taht way u could add a pull string to it and make it easyier.

2

I guess you could, never heard of anyone doing it before lol

3

I just ran a tubing out to a valve. Though you could, some PSVs dont like that, as it compresses the spring. And over time it wont hold what it once did.