Washing domestic device drain problem? I recently bought an outmoded remodel house. I installed a new...

I recently bought an outmoded remodel house. I installed a new washer and dryer. the first time I run the washer, water overflowed from the drain splash.

there is no vent on the drain string and there are two "firm 90 degree" fittings on the drain line prior to the p-trap.

I call American Home Shield, their plumber would not fix because it was not up to code.

Could the strong 90 degree fittings inflict the high pressure wet from the washer to back up. Is a vent really crucial for a washer ?

The plumber estimated that it would cost $2500 to bring up to code. I don't necessarily want the thing to code, I only just want it to work.
Answers:    "Could the hard 90 level fittings cause the high-ranking pressure water from the washer to wager on up?"
Yes.
Either repipe, eliminating the elbows or
try the drain hose extension suggested above.

"Is a vent really mandatory for a washer?"
Yes.
In addition to the upper air gap required where on earth the drain hose enters the drain strip (usually a standpipe)
the drain line requires a vent on the drain side of the P trap.

Try calling another plumber for this 'repair'.
I don't know if this will help out, but it fixed mine. I had alike problem, and had a friend who is a plumber look at it. He primarily added a piece of pipe on to the end of the washer hose so it go farther down into the drain. He added about 4 inches by clamping a brass pipe roughly speaking 6 or 7 inches long a couple inches up in the washer hose division so it sticks out 4 or 5 inches past the plastic. Then slide the brass down the drain so the hose down doesn't back up. It doesn't nouns like it would work, but it did for me. And it be pretty much free, so why not try? Good luck.