I just had a Rheem exterior tankless gas water heater installed on my house in Seattle. The installer used flex hoses for both gas line and waters line. The water lines are corrugated stainless steel, and the label says "for interior use only" but says nothing about connecting to a tankless water heater. The label on the corrugated copper ones at the hardware store does not specify you can't use it for exterior use, but it says "don't connect to a tankless hater heater." Terry, in another post on this website, says that in Seattle flex hoses are required. Are the stainless hoses OK? Are copper ones OK? Thanks for any assistance.
Water lines for exterior tankless gas water heater in Seattle
- Thread starter Vishnu
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An exterior tankless in Seattle? It does freeze here.
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Jadnashua
Retired Defense Industry Engineer xxx
The flex connection is (I think) there because on a tank, it could move independent of the supply, thus, the flexibility should help prevent things from getting torn off during an earthquake.
On your tankless, the thing is bolted to the wall and the piping will move with it, not separately. I've not looked at the code for that area...they may have some different ideas about what's required.
SOme tankless systems monitor for freezing and will run to prevent the INTERNAL piping from freezing, but that may not be enough for the supply lines to stay above freezing. If they're hanging out, I'd be worried. Keep in mind that insulation doesn't create any heat, it just slows it from escaping.
On your tankless, the thing is bolted to the wall and the piping will move with it, not separately. I've not looked at the code for that area...they may have some different ideas about what's required.
SOme tankless systems monitor for freezing and will run to prevent the INTERNAL piping from freezing, but that may not be enough for the supply lines to stay above freezing. If they're hanging out, I'd be worried. Keep in mind that insulation doesn't create any heat, it just slows it from escaping.
Fitter30
Well-Known Member
Need to heat trace and insulate both water lines. For the heater itself use a silicone heating pad like one made for a automotive oil pan. And if you lose power hopefully letting water run will help with freeze protection.
Not only does it freeze- it sometimes hits single digits F.
On a windy day during a cold snap it's too likely to freeze & break the heat exchanger, even WITH trace heaters. Heat exchangers work in both directions- it takes a lot of heat to overcome the effects of frigid air moving through the heat exchanger, and no real way to stop the wind-driven air currents in an outdoor unit.
I know of an INDOOR tankless in Montana where the heat exchanger froze and cracked on a windy (but still above zero) winter night, despite the unit having internal freeze protection controls, and no interruption of power.
This thing isn't likely to go anywhere near it's warranty period, and freeze damage probably isn't warranteed. Since it's already installed there aren't any great solutions here, unless you're willing to start over and go with an indoor model (indoors, where it belongs.)
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