Hi --

To replace a broken valve on one my radiators, I've drained the
water from the hot water heating system in my house. Now I don't
know how to refill it! Can anyone help?

I understand that there are manual and automatic filling systems.
In either case, must the boiler be on for it to fill? (It is
not on now.) All the water supply valves leading to the boiler
are already on. However, inline with the supply pipes, there is
also what looks like a pressure regulator with a little lever on
top. I didn't know if that might be a pressure relief mechanism
or if perhaps lifting the lever might allow the water to flow.
Any ideas? I can take pictures if that would help.

Thanks!
-Bob