Using my feet/shoe, the pipes measured 21.5'. They are already threaded. I would not use without doing a proper pressure test. Everything I do whether DIY or professional will be to code and I have access to experts to help me. For the record (since mentioned) we have very low gas pressure here. I believe it is 60 psi before the meter and then reduced to 1-2psi. I know that you can plug it with a finger and nearly no resistance - I confirmed that when I installed a new water heater recently.
