Hi, I have two cistern tanks in my loft, a largish one and a slightly
smaller one, both sat right next to each other, now I'm wanting to
drain the smaller one because it's formed some scum on the water
surface and I want to give it a clean.

I'm sure when I replaced the ballcocks on both cisterns a few years
back, I just had to turn the taps on in the bathroom / flush toilet to
empty it (after I had turned the main water inlet off) however I tried
doing this over the weekend, but the water in the smaller cistern tank
never budged, infact it almost looks like no water has come from that
tank for a while, look at the FAQ's it suggest this tank has something
to do with the boiler/heating iirc, so, would this be the case and to
empty it what would be the best way ?

and on a side note, where would be the best place to pick up a cover
for a cistern tank, there sems to be a rip in the smaller tank one,
probably why it's started forming scum on the water surface.

apprication in advance for any pointers.

Regards,

Nik