Installing a standpipe washer drainage

[dsss]

The washer that came with the house was wired to drain directly into a branch of sewer, without a p-trap. The washer died and I would like to wire the new one properly.

The problem is that the sewer line is above ground in the basement and the washer is on the opposite side of the sink/ejector pump.
I dont want another sink or pump and would like to add a standpipe. I've made a diagram below, here are some points:

- The washing machine is rated to pump water to 8 feet (96")
- I will close the existing 2>1.5>1.25 entry point where hose direct plugs now.
- I will cut-in a 2" wye into the lower branch with the side entry parallel to ground.
- Add a 2" p-trap into the wye
- Add 2" 24" length pipe into p-trap (24" is reasonable max for clearance, I'll try to make it a few inches longer if I can)

The washer will need to pump the water to about 78" which is not much higher than it does now.

I would also like to add a safety studor mini-vent, just in case. I know there is a vent somewhere, but I am not sure if its close enough. Adding a new roof vent is not an option. My question is - do I add the vent before or after the ptrap/wye/standpipe? I am thinking another wye with vertical pipe that ends in a studor. Am I over-engineering it?

Thank you!

 

[breplum]

You’ll need a backflow device to prevent basement flooding if the sewer clogs. I don’t understand much of your drawing.
Vent with AAV can go to vertical from a combo on it’s back after the p trap.

 

[dsss]

Sorry about the drawing. It seems so clear to me - because i live it

Currently the washer is connected by hose (squiggly line into a 2~ wye in the vertical pipe that connects two branches.
The middle 2" branch then connects under incline into 4" main line.
The wye where the hose is connected is reduced from 2" to 1.5" to 1 1/4" into brass backflow preventer and then directly into the hose/washer.

My idea is to close this 2" wye with a cap. Cut into a wye into the inclined portion of the middle 2" and insert a standpipe into it (the rendering of standpipe sizes is on the right in the picture. It doesnt exist yet).

Thank you for the advice on location of the AAV, sounds like I can place it after the p-trap connection (closer to 2>4 connect).
Where would I put the backflow preventer? Would it be inside the standpipe? Something like flood-guard or backup float-valve? At what point in the standpipe should it be located? I wondering if it would restrict the water discharge?

In the attached picture is what I am trying to replace

P.S. something like this https://www.amazon.com/dp/B00CBIQE7C?psc=1&smid=A2L77EE7U53NWQ&ref_=chk_typ_imgToDp along the horizontal line after the standpipe (closer to main line)?

 

[breplum]

If I were cutting in a 4 x 2 wye, then the first thing off the 2" branch would be a backwater preventer. Since I've never seen one in two inch, then I would choose a 3" one, which makes my new choice a 4 x 3 wye instead of the 4 x 2. After the backwater preventer device, then bush down to two inch, then 2" combo on back for the vent, then straight into the p trap.
Also, you must have a loose 4" cap or sewer relief device on the sewer outside at the nearest cleanout.

 

[dsss]

Thank you @breplum you have giving me a lot to think about. If I understood you correctly you would add the connections to 4" main pipe. However, its cast-iron and way beyond my skill set. I was thinking about the 2" pipe marked with arrow in the photo:

 

[breplum]

That link to CANPLAS you had for the 2 inch back water is actually an item I have not run into, and yes that would be a good choice.