Installing a whole house main water shut-off ???

[Fairbreez]

I was under our '90 Friendship dbl wide a couple days ago. Was sure hoping the incoming water line was routed to the closet housing the HW heater, but no such luck. It is entering the belly about 10" from the toilet drain from the 2nd Bathroom. Any suggestions for how to find the 3/4" water line inside the house, so I can install a shut-off valve? All responses appreciated, thanks for the forum!

[Archie]

They may have ran the water line through the belly in order to keep the heat tape short. It still should enter the home near the water heater though and split off from there. I would check the water heater closet for the incoming line and install a shut off there.