i'm a h.v.ac man not a plummer,my problem is sewer smell all through house when washer is run.now the house is over 100yrs.old it has no vents running to roof,it has a pro-vent in middle of basement and one at washer stand pipe.what can i do???

Are you on a sewer line or septic tank? Either way the major problem is the washing machine. If you have glogged sewer or septic lines or a septic system that is nearly full the washer is displacing the methane gas with water and forcing it back into the house. Obviously the washer is drain a large amount of water into the system everytime it drains as opposed to the small amount that toilet or sink drains. Two recomendations, have your sewer drain lines "s*****" or septic system checked and look into having an adequate vent line installed even if ithas to run up the outside of you house as many old homes that were retrofitted with bathrooms did.

it is a septic system that was recently pumped.a plumber came in and took out one of the pro-vents farest away from washer dump and ran 1 1/2 vent up side of house.but left other 2 pro-vents in basement.

Sounds like you have a dry trap somewhere. As Facucetmann said the washer puts out a lot of water fairly fast. The pro-vent may not be big enough to allow for enough air to enter into the system. Also if you have S traps in the house they tend to loose their water faster then standard traps used today.

i have changed all traps in house.could it be the pro-vents in basement