I'm getting ready to replace my 20-year-old water heater, and was wondering if there are any OKC code regulations against using flexpipe from the NG source to the control box?

It looks like I should be able to reuse the copper flex tubing for the water lines themselves, so I don't expect much of a problem in putting in a similar-size replacement...

Any other not-so-obvious caveats before I dive in? It seems a pretty straightforward job....I've just not done one.

Thanks