Slow draining washer drain

The laundry drain backs up when the washing machine drains. Older cast iron pipes, with "u" style trap connected to vent pipe( drain pipe, trap, then vent pipe). I tried bladder style connected to garden hose to force clog, worked with garden hose water down drain, but still backs up when machine drains. Should I try badder down vent?

A couple of questions. Do you have a new washer? Has the drain worked OK in the past? What size is the standpipe? Newer washers empty water much faster than older models. Older standpipes and traps were commonly 1-1/2" diameter pipes. These are too small for the newer machines, so backups are common. New standpipes and traps should be 2" diameter. If the drain worked OK in the past and no changes to the machine have been made, your drain may be partly clogged. Forget about bladders, chemicals, and DIY hand snakes. You need a professional to properly auger the drain and totally clear the clog.

slow washer drain

This is a duplex that was empty for a couple of months, but has been in use now since October. No previous problems for the previous tenents; they had a new machine. They pipe looks to be 2" in diameter, and over 2ft in length, the trap is about 4" in length and connected directly to the vent.

I believe a plumber who can auger the drain clear to the street is in your future.

At least it will be the only proven effective method...
The plumber cleaning the drain that is!

Thanx everyone for your advice! It looks as though I'll be calling a plumber! I guess I can't do everything myself, even though I try

"A man's got to know his limitations." Clint Eastwood as Dirty Harry.

Am I to understand that you have a new tenant in the unit? I've seen washer stand pipes that have run clear before, suddenly back-up and overflow because of a change of (or too much of) laundry detergent and the line gets suds-locked. Often reducing the amount of detergent or changing brands will reduce the suds and the line will go back to draining normally.

Try running a full load, no soap, no clothing, just maximum water in the maching, run the spin cycle and see how it reacts. If it drains, it was suds problem. If it still backs up, call a local rooter guy and have the line jetted. Snaking will clear a clog but only jetting will remove the scale on the inside of the pipe.