I am trying to figure out a septic gas problem which only occurs with heavy rains. We have realized that there are no pea traps in the drainage line for the washing machine and the bath tub? Do we need to install some and would this help with the septic gas smell?

Thanks!

They must be trapped and vented. If there are no vents on the drain lines, you can use traps with air admittance valves (AAV traps)

Puff's correct! All Plumbing Codes Mandate that each fixture have a trap and that every trap shall be vented. If you have fixtures that aren't trapped and vented you have direct open connections to the sewer allowing sewer gas to enter your home. Have this looked after ASAP. Good luck, Tom