DIY Basement Bathroom - Plan OK?

Hello everyone - I've learned a tremendous amount reading this thread over the past few months as we've been designing and starting a basement remodel (teenager needs a mancave!)

It's a big project, with many moving parts - not least the plumbing. Our situation: 105 year old house in Seattle, main sewer exit is in basement through the wall about an inch above the floor.
Therefore need an ejector. Plan is for installation of bathroom - toilet, lav and shower, as well as a laundry, and next to this a small kitchen with a sink but no dishwasher or garbage disposal.

I've attached a (rather ineptly) drawn plan, done in powerpoint - hope it's clear. Blue are drains, yellow are vents, brown is effluent from ejector to main sewer. It enters the stack about 20" above the floor, into a new (to be built) 2' branch line cut into the 4" main stack with a santee.

You can't wet vent the shower through the washer. Only bath fixtures can be part of a wet vent
You can't use check valves or back flow preventers in that configuration, nor do you need to. Just a single check on the 2" outlet from the pump

Like this? (see below)

I know there needs to be a backflow preventer on the ejector, and a valve. I thought also that there needed to be one for the fixtures potentially exposed to flood from main sewer, for fixtures below nearest manhole, ie the kitchen sink off to the left, on the same 2' line as the ejector.

Oops - didn't take off the 'wet vent' label, hope not confusing.

In Seattle, the toilet needs a 2" vent. If you wet vent the lav over the toilet, it still needs to be 2"

In Seattle, they will want the 2" from the pump basin directly into the 4"
The kitchen will have to come in separately.

This is a classic example of how the DETAILS are what separates a plumber from just anybody. This OP has done a lof of homework and has a good start.

The DETAILS that have been filled in here....PRICELESS!!

Terry said:

In Seattle, they will want the 2" from the pump basin directly into the 4"
The kitchen will have to come in separately.

Click to expand...

Terry - so the effluent from the ejector enters the 4' stack with a 4x4x2 wye, or a santee? If I have this enter the stack a few feet above the floor, can I bring the kitchen sink into the stack below, with another 4x4x2 santee? Does the kitchen sink, being below grade need its own backflow preventer (I'm not sure where the location of the nearest manhole is)?

Terry said:

In Seattle, the toilet needs a 2" vent. If you wet vent the lav over the toilet, it still needs to be 2"

Click to expand...

Can I bring together the 2" toilet/lav vent, and the 1.5" shower and 1.5" laundry vents together in the overhead joist space, and then up and exit the roof as a singe 2" vent? Or does it need to get bigger when they come together? (I know the ejector needs its own, dedicated 2" vent all the way to the roof)

Kestrel said:

Like this? (see below)

Click to expand...

That second pic with one backflow preventer reminds me of a plumbing botch-up long ago. A truck scale was installed on the edge of a swamp. The sump pump under the scale was piped into the drain system of the building which had a flat roof. The drain line from the building froze and as a result, the sump pump almost filled the entire building. It looked like a fish tank with water half way up the windows.

I'd hate to see what sewage would be like.

LLigetfa said:

That second pic with one backflow preventer reminds me of a plumbing botch-up long ago....

I'd hate to see what sewage would be like.

Click to expand...

Where does the backflow preventer get located in a sewage ejector set up?

Is this how the Pump outflow should meet the stack?
Can a 4x4x2 santee be placed in the stack below, to accept the outflow from the next-door kitchen sink? Or is this ill advised? If I want the kitchen sink, should I run it too to the ejector?

Forgetting the man hole cover for a while, the kitchen and the basin enter the 4" line separately.

The vents for the bathroom can combine 6" above the flood level of the fixtures served. So yes, the ceiling would be fine.
Or anything above 42".

The check valve on the pump is there so that the pump doesn't run continuously.

If you need a back water valve for the main line of the home, (because you are lower then the manhole) then that would be on the main 4" line out and that would be for the entire home.

You don't normally see that done around here much, except for some homes on the water.

Terry said:

Forgetting the man hole cover for a while, the kitchen and the basin enter the 4" line separately.

The vents for the bathroom can combine 6" above the flood level of the fixtures served. So yes, the ceiling would be fine.
Or anything above 42".

The check valve on the pump is there so that the pump doesn't run continuously.

If you need a back water valve for the main line of the home, (because you are lower then the manhole) then that would be on the main 4" line out and that would be for the entire home.

You don't normally see that done around here much, except for some homes on the water.

Click to expand...

Thank you, Terry!
For connecting the ejector to the main stack, does it matter, wye or santee?
Is the location of the pump input into the stack dictated by the connections of the upstairs fixtures? That is, there is a main and a second floor above - and all the waste lines from both floors (two bathrooms, kitchen and laundry) enter the stack just below the first floor joists (ie at the basement ceiling level). Do I need to carry the ejector input to this level? Can the ejector tie into one of the horizontal 3" lines from the floor above?

Thanks for all the help!