I just built an outdoor natural gas fireplace. After construction I found that the flame gave off hardly any heat. After checking the gas pressure I found that I have less that 1 pound of pressure not the required 3-7 psi which would explain the low flame. Is there a way to increase the pressure in the gas line. Or is there a way to disassemble the gas line under the house to remove unneeded gas pipe, thus increasing the pressure? All of the appliances in the house are ran off the same gas line but are working optimally (including stove, double sided wall heater, on demand hot water heater)
If the pressure you're measuring is the static pressure, that is the pressure in the line with no gas flowing, that pressure is the same everywhere in the line. You cannot increase that pressure by removing unneeded gas pipe. Instead, you can try having the gas company adjust or replace your regulator.
If you're measuring the pressure while gas is flowing, you might have lines that are too small, long or bendy. You might also have a gas meter that's undersized or defective. I again suggest calling the gas company to see if the meter needs to be replaced.
I hate when people say this on a DIY site, but it's probably a good idea to call a pro. But the gas company should be happy to at least answer your questions, since you're trying to use more gas. If the meter or regulator needs service or replacement, they should do that for free.