Hi guys,

I'm trying to figure out what kind of valves I have here. I have a hot water
baseboard heating system. There are some valves in line that look like
they're a shutoff/gate of some kind.

They say "THRIFT" on one side, and "B V 3/4" on the other. They use a
standard screwdriver to turn them, and they'll turn all the way around, so I
assume you turn 90 degrees for open, and another 90 for closed.

http://www.diezfamily.us/images/bs/AUT_2702.JPG

Look just down and to the left of the main shutoff wall switch in the pic.
There are two of these valves next to each other on the vert lines.

How tight are these when closed, and what exactly are they used for?

Each zone has another valve at the end of it as well, with a lever for shut
off.

The reason I ask: I need to replace my circulator pump, and am wondering if
these little valves can be used to shut areas off, instead of draining the
whole system.

Thanks,

Tim