On Rheem’s residential electric and A.O. Smith’s residential gas tank heaters, the hot outlet and cold inlet are both 3/4" NPT (pipe thread). A flexible water heater connector can join each one to the house pipe: its heater end is 3/4" female pipe thread (FIP), and its other end has to match your pipe.
What pipe runs to the water heater?
Look at the pipes above the heater, past any flexible connectors.
The connector end you need
FIP x 3/4" sweat, or FIP x 7/8" compression
Either one fits 3/4" copper tube, which is 7/8" across the outside (1/2" copper is 5/8"). A female sweat end slips over the tube and is soldered; a male sweat end solders into a copper fitting; a compression end tightens on with its nut.
On the package: 3/4 in. FIP x 3/4 in. nom. sweat, or 3/4 in. FIP x 7/8 in. compression
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FIP x 3/4" PEX
BrassCraft’s braided connectors come with a crimp PEX, cold expansion PEX or push-connect end.
On the package: 3/4 in. FIP x 3/4 in. crimp or cold expansion PEX
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A threaded connector made for CPVC
A.O. Smith heaters take threaded connectors suited to CPVC at their connections, and no PVC.
On the package: 3/4 in. FIP x CPVC
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Start overThe connector end you need
FIP x FIP
Female pipe thread at both ends, to screw onto the heater and onto a male-threaded nipple on the pipe. BrassCraft also makes an FIP/MIP x FIP version whose supply end screws into a female thread as well.
On the package: 3/4 in. FIP x 3/4 in. FIP
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A.O. Smith heater threads are steel, and a dielectric fitting or union is recommended on them when the pipe is another material.
The heater end
- Rheem: the hot and cold connections are marked and are 3/4" NPT on all models of its residential electric heaters.
- A.O. Smith: its residential gas heaters take 3/4" NPT at the cold water inlet nipple and the hot water outlet nipple, and those threaded connections are steel.
- Heat traps: these energy-saving fittings sit in the hot and cold connections of some Rheem heaters and most A.O. Smith ones. Leave the heat traps in on A.O. Smith heaters.
Flexible connector ends
BrassCraft’s water heater connectors have 3/4" FIP on the heater end. The other end comes in these types:
| Other end | Meets |
|---|---|
| 3/4" FIP | A male-threaded nipple or fitting |
| 3/4" nominal sweat (7/8") | 3/4" copper tube, soldered |
| 7/8" compression | 3/4" copper tube, 7/8" across the outside, with no soldering |
| Crimp PEX or cold expansion PEX | 3/4" PEX, joined the way your PEX system is |
| Push connect or press connect | The pipe types that fitting’s maker lists |
BrassCraft’s Copper-Flex FIP x FIP connector comes in 12", 15", 18" and 24" lengths, is rated to 125 psi, and is for exposed locations only. On Rheem heaters, unions or flexible copper connectors on both lines let the heater be disconnected for service.
The IPC and IRC text says a flexible water connector under constant pressure has to meet ASME A112.18.6/CSA B125.6 and stay accessible. BrassCraft lists its braided connectors to that standard. Local code decides what applies where you live.
Dielectric unions and nipples
A dielectric fitting separates two different metals to stop corrosion at the joint. The makers and the codes say:
- A.O. Smith heaters: where the steel connections meet pipe of a different material, a dielectric fitting or a dielectric union to ASSE 1079 is recommended, and with copper pipe the unions must be dielectric. Local plumbing codes may require them.
- A dielectric waterway nipple isn’t the same part as a dielectric nipple. A dielectric waterway nipple won’t protect an A.O. Smith heater from corrosion.
- BrassCraft connectors have a built-in dielectric to keep different metals apart. With them, no separate dielectric union is needed.
- The code text joins copper tubing to galvanized steel pipe with a brass (copper-alloy) or dielectric fitting; the IPC also allows a dielectric union to ASSE 1079. Your building department decides what’s required at your heater.
Valve and soldering
- Shutoff valve: the IPC text calls for a full-open valve on the water supply to every water heater, and the IRC on the cold-water supply, at or near the heater. On A.O. Smith heaters, that valve is a full-flow ball or gate valve.
- No heat at the heater: heat on a Rheem heater’s hot or cold connection permanently damages the dip tube or heat traps, and A.O. Smith connections contain non-metallic parts that heat could damage. Solder copper to a threaded adapter first (about 12" of pipe in A.O. Smith’s instructions), then screw the adapter on.
Close the cold water valve and turn off the gas or the power to the heater before you disconnect anything, and let the water cool first. The gas line, venting and wiring are work for a qualified installer.
Joining copper, PEX and CPVC elsewhere?
Connecting different pipe