I am replacing my tankless with a new, more efficient unit. The connections/ piping on the current unit is 1/2". The connections on the new one is 3/4". Do I have to replace all of the piping going in and out to the house or can I just step up the size at the heater? I live in Greenville, TX.
Tankless replacement
- Thread starter DarylS1
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Step the water pipe size up or down as needed.
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Jadnashua
Retired Defense Industry Engineer xxx
You may not get the same gpm output if not fed by 3/4" supply.
What does the installation instructions have to say about that? They are the one you need to pay attention to. If it were say a tank, wouldn't matter except for maximum flow, but here, you need maximum flow to get maximum output since there is no tank to buffer the heat. Less water through the thing may mean it will not be able to ramp the burner up to full to get the gpm its rated for without overshooting and cutting back.
FWIW, a 1/2" line on hot isn't recommended to provide more than 4gpm according to the Copper Institute. 3/4" line doubles that. Can it, yes, should it, no.
The rules for fluid dynamics have been known for a long time...the free handbook from the Copper Institute pretty much covers the impacts and capabilities when using copper piping. If the pipe could handle more, they'd probably say it.
What does the installation instructions have to say about that? They are the one you need to pay attention to. If it were say a tank, wouldn't matter except for maximum flow, but here, you need maximum flow to get maximum output since there is no tank to buffer the heat. Less water through the thing may mean it will not be able to ramp the burner up to full to get the gpm its rated for without overshooting and cutting back.
FWIW, a 1/2" line on hot isn't recommended to provide more than 4gpm according to the Copper Institute. 3/4" line doubles that. Can it, yes, should it, no.
The rules for fluid dynamics have been known for a long time...the free handbook from the Copper Institute pretty much covers the impacts and capabilities when using copper piping. If the pipe could handle more, they'd probably say it.
