We are in the process of remodeling a basement in a 50 year old ranch house when the sewage line backed up into the shower basin next to the toilet. There was an outside sewage line protection policy in effect so we called & when the plumbers came they worked for many hours to unclog the line with a 3/4" eel. They felt the clog was 5' away from the shower drain where the toilet enters. They suggested we pay them 400$ to pressure wash the inside of the line from the outside vent in(approx. 50'). This house has iron or steel sewer lines & there is still a sewer gas smell & some toilet paper shreds showing up in the shower drain trap water. There is also sewer gas smell in a basement drain beyond the clog. We can flush the toilets & see the water flowing in the vent outside. Should I follow the plumbers advice or try some othe approach. Any Suggestions would be appreciated.