On Sunday, October 30, 2016 at 12:06:45 PM UTC-4, Ed Pawlowski wrote:
On 10/30/2016 10:44 AM, wendy vonlienen wrote:
am putting new floor under gas hot water heater,there is a hole in old
floor
under water heater for vent i think?can i cover it up


That vent may be very important. It may be the source of air for
combustion.

+1

If it's a gas WH in a closet, it could be critical. If it's in
a wide open basement, then it's not.