I have a front loading washing machine that when it drains will over flow the stand pipe,

The drain pipe is run to a drywell. I dug up pipe and there is no blockage, tank is not full, pipe is clear.

It seems to be the high pressure the water is pumped at fills standpipe and prevents air from escaping because the stand pipe fills up and then sometimes it’s like a burst of air forces the water out of the standpipe. A couple times the water came out of the vent.

Stand pipe is 2” vent pipe is 1-1/2”
Do I need a 2” vent pipe?


Here is Link to photo of set up.





Edited 2 times.

I'm not a plumber...

You said that sometimes water comes out the vent. That means it is easier for water to flow UP the vent pipe than DOWN the drain. That means there is probably still a blockage in the drain, below the point where the vent joins the standpipe.

The plumbers here frequently advise dumping a 5-gallon bucket of water down the drain to test how fast it flows.

Ran snake came up with nothing. Then attached camera ran camera found pipe half full water. We had 18” of snow that melted ground has been soft so it looks like drywell is full. I should have known as this happened a few years ago after had 2’ of snow melt. What had me was the machine on the first high speed drain would back up this is when the most water is put out. Then the other drains during the spin cycle would drain with no problem because they were small amounts of water. Looks like I’ll be getting the backhoe out and adding another tank and bigger drain field.