Heya I'm a total novice at diy, having just bought my first house. Sorry for the dumb question that follows. I've drained and removed a couple of large rads for decorating, but now they're back on, I'm unsure if I need to refill the loft tank somehow to make up for the water lost? It's a very old conventional boiler, with tank in the loft so gravity fed. Will the system just refill itself to it's previous level, or is there something I need to to do to make it happen? Thanks in advance!