Answers and Analysis

Are all direct vent type water heaters constructed with sealed combustion chambers?

What is the definition of a vent connector? My concern is the breaking point between the vent connector and the appliance vent. I realize that the breaking point may be when converting from a single wall
connector to a double wall (Type B or L) vent. What if the person decides to use a double wall vent
connector? Section 510.7 (2003/2006/2009) 509.7 (2012) has provisions for single wall connectors which are not allowed in concealed spaces. Is a double wall connector allowed in concealed spaces?

Does the code allow direct vent water heaters to be installed in bathrooms and bedrooms?

Does an existing gas water heater in a bathroom have to be relocated if a new yard line is installed, or if for any reason the gas meter is relocated or new gas piping is installed?

Is it permissible to install a gas-fired water heater in a closet which opens into a public restroom which has no bathing facilities?

This question is regarding the location of a L.P.G. water heater in a laundry room which constitutes a confined space. The laundry room has two doors, one into the hall, and the other door into the bathroom.
The only means of access into the bedroom is through the laundry room. Would this installation of a gas fired
water heater in the laundry room be allowed by Section 505.1 (2003/2006/2009) 504.1 (2012)?

Can a gas water heater be located in a hallway closet where the hallway opens into bedrooms? The door on the closet has louvers.

Is a gas-fired water heater allowed to be installed in a half bath which has no shower or bathtub?

What constitutes an over-temperature safety protection device? Must the device be a pressure and temperature relief valve or can it be some other type of electrical device?

Would the use of a pressure and temperature relief valve meet the Code requirement of Section 506.2 (2003/2006/2009) 505.2 (2012) for when a heat exchanger fitting is used in a wood burning room heater with a storage tank?

Does the plumbing code require that the entire combustion air openings be located within 12 inches of the floor and within 12 inches of the ceiling of the heater enclosure or does the code permit that a portion of
the combustion air opening be located within 12 inches of the floor or ceiling with the balance of the
opening permitted to be more than 12 inches above the floor (or more than 12 inches below the ceiling)?

What constitutes the appropriate location of anchors or strapping in the upper and lower third of a water heater for safety and the requirements to maintain a minimum of 4 inches above the gas control valve or connection?

Are safe pans required for attic installations of tankless water heaters?

A replacement water heater in a residence was installed inside a utility room, located approximately 12 to 15 feet from the building exterior. The building construction is a conventional raised floor with a crawl
space. The water heater is installed in a pan. The temperature and pressure relief valve terminates into the
pan which is drained into the crawl space.
The Code states that the pan shall drain to an approved location. Can the pan drain into the crawl
space, as opposed to being piped to the building exterior?

Could the drain from a water-tight pan that is required under a water heater be discharged to a tailpiece of a lavatory or to an approved accessible inlet on a bathtub overflow as provided in Section 807.2
(2003/2006/2009/2012) for condensate waste from air conditioning coils?

Does the term "floor-ceiling" and "floor-subfloor" mean that a 'water-tight pan' is required on all floors of a building except for slab on grade locations?

Can the watertight pan requirement be waived for tankless water heaters for the following reasons: A tankless water heater without an integrated storage tank that is installed in an attic would not cause
any more damage from leaking than a water distribution piping system installed in the attic.
Tankless water heaters are not constructed the same as conventional storage type water heaters,
therefore a water tight pan should not be required underneath tankless water heaters.

Section 508.14(1) (2003/2006/2009) 507.13 (2012) states: "Gas utilization equipment in residential garages and in adjacent spaces that open to the garage and are not part of the living space of a dwelling unit shall be installed so that all burners and burner-ignition devices are located not less than 18 inches above the floor unless listed as flammable vapor ignition resistant."
Since the UMC specifically points out heating and cooling in garages and does not address domestic
clothes dryers, does the UPC consider gas fired domestic clothes dryers to be "gas utilization equipment"
as stated in this section?

The Code requires water heaters generating a glow or spark or flame capable of igniting flammable vapors to be installed in a garage, provided that the pilots and burners or heating elements and switches are at
least 18 inches above the floor level in residential garages.
The Code further states, “when such water heaters installed within a garage are enclosed in a separate,
approved compartment having access only from outside of the garage, such water heaters may be
installed at floor level, provided the required combustion air is also taken from the exterior of the garage.”
Would the requirements of the Code apply to a water heater located in a room adjacent to a residential
garage if the door of this room opens directly into the garage?

Would a garage wall separation, similar to the one shown in Figure 1, qualify the utility room as part of the residential occupancy and thus not require pilots, burners or heating elements and switches to be installed
at least 18 inches above the floor level? The separation is normally not weatherstripped. Would the interpretation change if it were weatherstripped?
Figure 2 depicts the utility room as part of the residential occupancy. Would the utility room be considered
part of the garage and thus require an 18-inch elevation?

In the 2006 UPC, Section 510.3.4.4 (2003/2006/2009) 509.10.3.2 (2012), states "Vent connectors serving equipment vented by natural draft shall not be connected into any portion of mechanical draft systems operating under positive pressure." Could you please define "positive pressure" in this case? When I read this section, it contradicts with Tables 5-14 through 5-17 (2003/2006/2009) Tables 510.2(1) thru 510.2(4) (2012) where the combination of mechanical fan and natural vents are allowed. Please clarify.

Can single wall metal pipe be used in dwellings and residential occupancies as a vent connector? In an attached U Occupancy?

Can the venting system for three water heaters be sized using the alternate method of the area of the largest connector, plus 50 percent of the area of the smaller connector?

If potable water, or a fluid with toxicity rating of 1, is used as the heating transfer medium within a solar water heating system (and the heat exchanger is not connected to a boiler) is a single-wall heat exchanger
permitted by the UPC and USEC?

Prohibited Use. Single-Wall metal pipe shall not be used as a vent in dwellings, and residential occupancy. Was the intent of this Section to require double wall metal vent connectors as well? Or does this section only apply to double wall vents?

Condition: installed in a residential garage, is a water heater, listed as Flammable Vapor Ignition Resistant.
Are burner and burner ignition devices required to be located not less than 18 inches above the floor?

Section 507.5 states: Discharge from a relief valve into a water heater pan shall be prohibited

1. Why can't the pan be used as an indirect receptor if the pan has a drain line running to a floor drain?

What is meant by "provided the closet is equipped with a listed, gasketed door assembly and a listed self closing device"?

Comment:
What exactly is a listed door? This is not requiring a UL Rating is it, (seeing as how that's not stated)?

Does the requirement for “water heaters shall be anchored or strapped to resist horizontal displacement due to earthquake motion" apply to electric water heaters or only gas fired water heaters?

Does an on-demand water heater with approx. 2-gallon capacity, installed in a cabinet, under a kitchen sink, require a drip/drainage pan to be installed under it?

Are single wall heat exchangers permissible with R410a refrigerant based domestic hot water heaters?

Comment:
The SDS (safety data sheets) for R410a the polyester oils in the refrigerant indicate mild toxicity and the remedy for ingesting is "treat systematically."
We cannot find FDA guidance on these materials so the SDS sheets appear to be our best guidance. In addition to the fluid toxicity, the application must matter. Refrigerant system run at high pressures and do not like water. If a system leaked, some small amount of refrigerant is guaranteed to enter the potable water but if a leak occurred, the pressure loss would be rapid which would shut down the system.
Also, with our proposed active safeties, it is doubtful any refrigerant or oil could make its way into the domestic hot water storage tanks. We propose the following alternate path to ensure safety of refrigerant based domestic hot water (DHW) heater systems.
As an alternate to double wall heat exchangers (which are inefficient and expensive), we would like to use a check valve (double check is fine) on the inlet to the heat exchanger (HXR) and a normally closed (N/C) motorized valve on the outlet of the HXR. If the refrigerant low-pressure switch is engaged, it would close the motorized valve and power off the circulation pumps to the DHW storage tanks. If the unit lost power, the N.C. motorized valve would close.
Given the relatively low toxicity of R410a and the oils within it, the small amount that could potentially leak into the DHW system, and the default safety of this "active safety system", we feel this solution meets the intent of the code while providing an efficient and cost effective solution to sufficiently address the safety concerns.

1. Is this no longer allowed for single appliances unless the flue is encapsulated? (see comments)
2. Are there other tables that can be used to properly size flues or chimneys exposed to the outside?

Comments:
section 510.1.10(along with its equivalent section 803.1.10 in the UMC) does not allow the single appliance tables for type B and masonry chimneys to be used to size chimneys and flues if 'exposed to the outdoors below the roof line' unless 'passing through an unventilated enclosure or chase insulated to a value of not less than r-8.' 'where vents extend outdoors above the roof more than 5 feet than required by table 509.6.1...the outdoor portion of the vent shall be enclosed...' we have been allowing type B vents on the exterior of the building for a long time.

Does an on-demand water heater with approx. 2-gallon capacity, installed in a cabinet, under a kitchen sink, require a drip/drainage pan to be installed under it?

Does Section 507.26 require a permanent ladder to be provided to reach a lowboy electric water heater installed 6 feet above the floor?

1. Are anchor and strapping requirements mandatory for all water heater installations, regardless of the state or geographic region?

Comment:
Seismic categories C, D, E and F have been removed, makes anchor and strapping requirements mandatory for all installations.

1. Is it the intent of this section to prohibit fuel fired appliances in rooms that contain bathroom fixtures (lavatories, toilets, showers, bidets, and tubs as well as any combination thereof)?

Comment:
With some exceptions this section prohibits fuel fired appliances in bedroom and bathrooms but does not include half bathrooms in the list of prohibited locations.

Does the drainage pan requirement apply to a concrete multi-story building where the floor is structural concrete and the ceiling below is suspended drywall?