Hot water storage tank - drain valve?

[Amlangford]

I have a pumped central heating system in my house (about 12yrs old). The hot water cylinder is in the bathroom and the header and feed and expansion tanks directly above in the loft. In passing I noticed that the drain valve on the cylinder (22mm dia pipe exiting from bottom of cylinder) is open! What is the purpose of this valve? If its to facilitate drainage of the cylinder, shouldnt it be closed under normal working conditions??

Cheers,

 

[hj]

valve

You need a local plumber to check it. British systems are entirely different than U.S.A. ones.