I am installing a new wash machine outlet box and drain line in my 1st floor bathroom,it will run straight down to the basement. Will I need a p trap and vent in this line.

Yes, you will need 2" trap with at 30" stand pipe and at least 1 1/2" vent.

Let us know if you need help with designing your new drain / vent system.

Back to you... Milo

I have the 2 inch diameter pipe line with the trap, but I don't have the vent. Could I put a vent in the drain line.Or would I have to run another line up the wall with the vent at the top,and an air grate in the wall.

A legal vent needs to run up the wall and connect into other vents in the house or it can penetrate the roof by itself (2" pipe size minimum to penetrate roof).

An illegal vent, called an AAV (mechanical air admittance valve) can be installed... allows air in only when needed. An AAV must remain accessible at all times so it can replaced if it ever fails.

Install the PTRAP off a sanitary tee fitting and continue the vent pipe straight up and install the AAV at the same height as the PTRAP standpipe is tall, OK?

More questions? Let us know...

Mark

Ok And thank you Milo for all your help.

In Ohio AAV vents are legal. You can buy a AAV box that goes in the wall and a grill goes over it for access. It is similar to a washing machine drain box. Use a sanitary tee with a trap that goes up to the drain and go from the top of the sanitary tee to the AAV box.