Space under water heater
 

We opened ours up years ago. Yes, there is open space but not for large bins.

You cannot open that up for storage. It is your return air box. Any one of the air conditioning vendors will tell you this. This chamber is sealed fir air handling.

If you need that small space for storage and plan on getting on your hands and knees when you need something it’s time to get rid of some stuff

In our patio villa, the space is a plenum for the air returning to the AC.

Gas hot water heaters are elevated to prevent ignition of gasoline fumes that may be emitted from storage of gasoline in the garage. Apparently they are concentrated a foot, or so from the floor and up.

Where was the water coming from?

It used to be code that water heaters with pilot lights had to be elevated in case of gasoline drips from cars, but that has changed. See quote below:

“ Only older gas water heaters located in a garage are required by the International Residential Code (IRC) and Florida Building Code (FBC M1307.3) to be elevated. It is not necessary for electric water heaters or gas water heaters manufactured after mid-2003.

The code states that “appliances having an ignition source shall be elevated not less than 18 inches (457 mm) above the floor in garages,” and the purpose of this stipulation is fire safety. Any gasoline leaking from a car parked in the garage creates flammable fumes that are heavier than air and settle near the floor. An open flame close to the floor, like the pilot light in a water heater, can set off an explosion and subsequent house

But, even with the requirement to elevate any source of ignition up above the floor, numerous house fires continued to be attributed to the gasoline fume ignition in the garage. So the Consumer Products Safety Commission (CPSC) mandated that all 30, 40, and 50 gallon gas-fired water heaters manufactured after July 1, 2003, have Flammable Vapor Ignition Resistant (FVIR) technology.”

From: Are water heaters required to be raised off the floor?

There seem to be various designs. In my garage (see photo below), a fan sucks household air through the return duct and the filter on the left, down into that enclosed area, where there is a ductwork box, and it blows it through the heater/air conditioner unit on the right and back through the house. Some houses may have room for storage there, but not all. I agree with the responder who said to pull out your air filter and shine a light inside and see if the ductwork extends down or directly to the side and into the heater/ac.

Thanks Warren. Now I understand the reason for it.

If your water heater is teaching an age where replacement is in sight (5-7 years), I’d recommend replacing it with a tankless water heater. They are wall-mounted and create quite a bit of useable floor space. Plus they’ll reduce your gas bill noticeably.

In many cases the space underneath your hvac system is part of the return. If you open it your hvac system will suck in the air from the garage instead of from the returns inside your house. You can see if this is the case by opening up your system where the filter is. Yes the area underneath is part of your return you should be able to look in there by pulling the filter out.

Water heater
 

5 to 7 years? I am getting ready to replace my gas water heater ( i have not had a problem with it) and it is 19 years old.

Hi I am interested in enclosing my furnace as you described. Can I asked who you used to do that and would you by any chance have any pictures that you could share? My wife really want this done and I am hoping it os something I could do myself. Any assistance would be appreciated Thanks Jon. 716-713-1568

We have a Lantana model with the water heater in a closet in the garage. We lived on a sailboat and every square inch of space, hidden or not, was utilized. Same when we moved here. Husband opened up the space under the platform, built a door for it and uses it to store stuff.

The part of mine under the furnace unit is an air duct that the air travels as it moves up into the unit. It's lined with a coated material, and I've had problems with water building up in it.