Beginning July 1, 2003, US water heater manufacturers will be changing the basic design of gas-fired residential water heaters of 75,000 btu's or less.

The new regulations were adopted by the US Dept. of Energy under ANSI Code 221.10.1-2001.  The new design will be required on all water heaters manufactured in the US after July 1, 2003, according to the following schedule:

Note:  Canada will require similar changes six months behind the US.

The new standard will not require replacement of existing units, and older models remaining in inventory in distributors warehouses can continue to be sold until depleted.

The cost of these new units will be considerably higher than existing units, possible as much as 50%.

Current designs expose burner flames to household air, including any flammable vapors that might result from an accidental spillage of gasoline or paint thinner.  That could result in catastrophe should these vapors come in contact with the combustion flame.

A rupture in a natural gas line elsewhere in the house could pose a similar hazard.  While explosions are rare, the US Consumer Products Safety Commission in 1994 attributed 2000 fires a year to the ignition of ambient flammable vapors.

In an effort to safeguard the home against this risk, a new type of combustion changer has been developed that traps inlet air and keeps burning vapors from escaping into the room where a fast-spreading fire may result.

This is accomplished by means of an arrestor plate, which is a perforated steel plate that controls the burning of vapors and prevents flashback into the room.  It is augmented by a series of baffles that prevent lint, dust, and oil from clogging it.

Provided by Stearns