Washer stopped draining.

[BillnLonda]

We survived the cold blast with no evident problems but now the washer overflows and will not drain. When we lost power I drained all the water lines but there was most likely water in the p trap on the washer discharge.
2018 Montana 3791RD with dealer installed Splendide ARWXF129W stackable washer / dryer.
The discharge hose is intact and is properly placed in the drain.
It doesn’t start to overflow right away and when it does it leaks out over the hitch area and not into the living area. I checked the clean out in the basement and it looks fine with no backed up water. I have removed the washer /dryer and there is no cracked or broken piping visible.
My only thought now is it could be the vent.
Anyone have an alternative theory or have experienced this first hand?

[RMcNeal]

I have a 2019 3791RD but have not used the W/D hookups. The drain pipe on mine is visible in the passthrough basement overhead. It comes straight down and turns back to go to whichever tank it drains. I haven't found out yet as I am still on the fence with putting in the stackable W/D. If yours is draining under the hitch area, I wonder how it is getting up there to run out? Maybe running forward in the floor area of the closet? I'd try snaking the pipe if you can to see what's going on. I had read there is supposed to be a Hepvo valve somewhere but I haven't found it, really haven't looked either. Maybe it could be frozen up and blocked?

[Daryles]

Here are pictures of the plumbing behind the cap and under the shelf in the closet.
Its not hard to remove the shelf in the closet to get to the HEPVO valve underneath (white thing in the background).
Do not snake HEPVO valves. It can damage the membrane inside.
https://hepvo.com/

[BillnLonda]

Problem solved. Thank you sir!

[Daryles]

Was it the HEPVO?

[BillnLonda]

Yes it was. The membrane had gotten pushed back up into the housing.