i have a hole under my hot water heater that is 5 inches wide that goes outside can i cover it up

[wendy vonlienen]

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

[Jack G.]

If you use natural gas it could be a safety issue and I would check with your local gas company.

[Ed Pawlowski]

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

[Retired]

It might be a floor drain in case of water leak, or TP valve release

[Paintedcow]

The OP never mentioned the type of water heater. If it's gas, it may need the combustion air. If electric, it's NOT needed for combustion. However, all water heaters need some sort of drain in case of a leak. Normally, if it's a drain, buy a plastic or metal base. (Pan under the heater). Those drain outside with a piece of pipe.

[philo]

Yep. When they fail, there is generally a fairly good sized leak.

I would leave the hole there and make sure there is nothing below it

[trader_4]

+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.

[AL]

My last house (built in 59) had the gas water heater and gas furnace inside the same closet located inside the house. The vent was a grill in the closet door. Lived there 30 years and never once flooded the house. Came close one time though. Happened to hear a hissing noise and saw a tiny leak spurting out. The water hadn't left the closet yet so I was very lucky.

BTW that model furnace had two doors, top-burner-vented and bottom-fan-sealed. No interlock. People would sometimes leave off the bottom door after cleaning/repairing the fan. The fan would then suck in the gasses from the burner compartment above and spread them throughout the house. That furnace was used in thousands of houses in the area and caused many medical problems over the years.

[Ameri-Clean]

To summarize: if it is a vent to draw in combustion air, it is needed if th e water heater space is small or airtight or if you don't want to use heate d/cooled house air for comubustion. If it is a drain in case of a leak, you may someday wish you still had it. I assume there is some protection from insects or rodents entering the house through this hole.