Question: Hi! These questions may be a bit out of the norm, but here goes...We recently purchased and installed a multi-oil furnace in my husband's shop. We came across some directions about measuring the "draft over fire." We know we need a draft meter to do this, but whom could we contact in order to purchase one? Also, we know from reading the manual for the furnace that a draft meter measures in "w.c.," or water column. We are interested in the origin and specifics of this unit of measurement. Can you enlighten us? Answer: A draft meter can be purchased at any plumbing and/or heating supply. Draft over fire refers to the fact that you should check the draft when the unit is firing. Water Column is a measurement of pressure, where 28" WC = 1 PSI. Since draft is a very low pressure, WC is used. I assume the origin is how far up a tube that a column of water would be drawn.