I have a 5v40-7p water heater. can i convert to nt gas

Yes it can be converted, however you cannot buy orifice, will require a license.
https://www.rinnai.us/faq/tankless-water-heater/can-a-rinnai-tankless-water-heater-be-converted-to-a-different-gas-type

With knowledge of make and model, your manufacturer can supply a retailer who can provide you with proper kit...
info here...
http://www.propane101.com/lpgasapplianceconversions.htm

http://hometips.me/Mar/Convert-water-heater-to%20different-gas.pdf

Sears com

Contact Rinna
Some water heaters allows changeover by installing new chipboard or changing dip switches... some do not.
Propane burns much hotter with higher pressure than natural gas
Gene

Water Heater Timers Save Money

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Rheem water heaters should not be converted from propane to natural gas. The burners have been optimized for the rated gas and will not work as well after conversion. (Unlike ranges where the gas/air flow ratios can be adjusted when the burner orifices and regulator are swapped, the water heater doesn't have that option.)

I wish I had better news for you. I recommend you get a new water heater for the LNG service; it will be safer and more efficient.

Cindy Wells

no.
propane burns much hotter than natural gas, and has higher pressure
gas valve and burner and orifice must be changed to switch between natural gas and propane
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html
Most manufacturers do not support converting gas on heater.

Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Call Rheem, they do not support gas change on all models:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html

Gene

Water Heater Timers Save Money

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Sell it on ebay.

A simple chip change will not convert because the orifice for each gas is different, the gas control valve is different, NG and LP gas each burn at different temperatures and pressures... with propane having higher temps and pressures.

Don't buy tankless computers and expect trouble-free installation and water heating bliss afterwards.
Read the manual for maintenance requirements, and look at the parts sheet and ask yourself how such a complex machine will simply balance and monitor water flow, water pressure, incoming and outgoing water temperatures, gas pressures, vent pressures, gas quality, gas pressures, while connected to water, gas, venting and electric systems inside your home which each have innumerable problems on their own.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Install tank type heater for around $400 and live worry free.
Avoid Rheem products since they do not post service manuals.
http://waterheatertimer.org/Which-is-best-gas-water-heater.html

Gene
h

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

A registered gas installer can obtain parts through Rinnai stockists and convert most heaters.

This unit cannot be converted from gas type to gas type.