Rinnai water heater install

[metolent]

Hi,

My shiny new Rinnai on-demand water heater just arrived and I plan to install it this weekend.  I've got black pipe for LP run over near where it is going to be mounted in the crawl space.  However, I wanted to learn which is the preferred way to connect the last section of gas piping to the unit -

1) hard pipe it directly to the unit (black pipe it all w/ appropriate drip leg and shut-off valve of course)
or
2) black pipe except after the shut-off valve, then a flex line to the actual w/h.

I've seen them both ways - just curious if one is preferred over the other.  What would you do?

thanks!

[Danfish]

Getting everything lined up for the hard pipe connection from shutoff valve to appliance can be a challenge.  Using approved flex connector makes life easier.

[davidj]

Some places don't let you put LP appliances in crawl spaces.  If the code isn't an issue, I'd still make sure that you have a way for leaking gas to escape - it's heavier than air and can pool to the point it becomes explosive if there's not a way for it to escape (e.g. via a floor-level vent).

I'm using 7/8" OD flexible connection and a 3/4" FIP->FIP valve (both of which aren't available in some hardware stores, so you might need to shop around).  Note that the 3/4" FIP->flare valves are typically for 5/8" tubing, which isn't rated for an e.g. 200K BTU water heater.

[davidj]

And iirc, the drip leg should be after the valve.  I.e. black pipe->valve->flexible->drip leg->water heater.

Note that I have fully-installed exactly zero gas appliances in my life (have everything in place but still haven't got propane yet) so my advice is worth what you paid for it 

[Alan Gage]

I think it was the Des Moines register had a big story recently about flexible gas line. They've been having problems with them developing pinhole leaks when hit by lightning and burning down houses. Apparently the lines don't have to be grounded so when hit by lightning the leak develops when the charge jumps from the flexible line to a ground.

Did some looking and found the link:

http://www.desmoinesregister.com/article/20110722/NEWS/107220333/Thousands-Iowa-homes-fire-risk-from-gas-tubing

Just something to think about.

Alan