Saniflo discharge-plumber installed incorrectly?

[Help me out]

Wanting to add a half bath on a slab without cutting concrete. Planning to use saniflo access 3 macerating toilet/pump. The discharge line from the saniflo is 3/4 in and it says to tie it into the the main or a stack but didn’t specify minimum size that I can find. The stack on this side of the house appears to be 2 inches and the only other thing draining into it is a washing machine drain. Since it is coming out of a 3/4 in pipe, is this 2 in stack sufficient for the connection?

If this works do you drain the saniflo into the stack above or below where the washing machine tied in?

 

[Terry]

The saniflo would tie in below the venting for the trap arm on the washer.

2.7 - SEWER PIPE (COPPER, CAST IRON, PVC, ABS) 1.Install an appropriate wye fitting into the sewer pipe, (with  1 1/2" branch hub). 2. Read point 3a first if using a copper wye. Glue a bushing, ((spigot x FPT) 1 1/2" x 3/4") into the 1 1/2" hub of the Y fitting.

The washer will be 2", so a 2x1.5 wye looks to be it, bushed down to 3/4"

 

[Sponsor]

 

[Help me out]

The saniflo would tie in below the venting for the trap arm on the washer.

2.7 - SEWER PIPE (COPPER, CAST IRON, PVC, ABS) 1.Install an appropriate wye fitting into the sewer pipe, (with  1 1/2" branch hub). 2. Read point 3a first if using a copper wye. Glue a bushing, ((spigot x FPT) 1 1/2" x 3/4") into the 1 1/2" hub of the Y fitting.

The washer will be 2", so a 2x1.5 wye looks to be it, bushed down to 3/4"

Thanks for the prompt reply. This is a dumb follow up question but to make sure I’m understanding correctly can you look at the drawing attached and say if I connect the saniflo and point a (above) or point b (below)
Also can I tie the saniflo vent in a pictured or would I need to run a sevin vent through the roof?

 

[Terry]

The vent ties in at 6" above the highest flood level of the fixtures served. Normally about 42"
The drain goes "below" the santee for the washer p-trap. That would be close to the floor.

 

[Help me out]

The vent ties in at 6" above the highest flood level of the fixtures served. Normally about 42"
The drain goes "below" the santee for the washer p-trap. That would be close to the floor.

I’ve got the vent above like you suggested but there really isn’t room to have the washer standpipe tall enough and then run the saniflo drain tie in lower.

is it ok if the saniflo wye is above the washing machine wye?

I had plumbers install it but think they maybe did it wrong. I’m thinking if the saniflo is above the laundry like currently installed, the laundry needs a separate vent?