We have a weekend house in the country with a septic system. It has a basement and in the utility room, a water softener and heat pump/furnace. The drain for the heat pump and water softener go into the floor drain now. The problem is the floor drain is a French drain discharging above ground which freezes in the winter because of the slow running water from the fiurnace/humidifier causing water to back up into the house. A major problem if it freezes and the softner needs to regnerate. I know I could rent a backhoe, dig a trench about 100 feet long, and get gravel and bury and extended outside line that would drain into the gravel bed and not freeze but that is a lot of money and effort to get a backhoe and gravel to this place.

Right now the Softener drains into a 2" PVC Pipe run vertically about 2 1/2 feet up the wall next to the softener and then around the floor and into the floor drain. I would like to consider teeing the two drains into the vertical sewer pipe and just run them into the septic system. I think I would raise the existing 2" PVC pipe up and run the 2” PVC around the wall slightly below the level of the water outlet from the furnace system (to T the furnace into that line as well) and then T the 2" line into the vertical sewer line. It is PVC 4” line. I tried attaching a drawing.

So questions:

I assume I need to put a trap into the 2” line before it goes into the sewer?

Do I vent the line before it goes into the sewer and after the trap (or before the trap) in some way and if so HOW?

How do I T into the 4” PVC Line ? It is fixed above and below where I would T in and I don’t see how I could get a standard 4” PVC T onto it. - Do I cut out larger section and use rubber joints to connect the T in? I read about "no hub" connectors - is that what I need (not sure how they would work)?

An aside, I assume draining the softener into the septic system is not a problem from what I have read but if it is let me know. All you really have is the regeneration draining into it – 40+ gallons about once a week or less.

Hey Jeff,
What do you mean when you say,

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it is fixed above and below where I would T in

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What's fixed? Please explain.
You also ask,

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How do I T into the 4” PVC Line ?

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Are you intending on raising the new floor drain,(see image) on a platform and teeing into the stack or cutting into the cement and teeing into the 4" line as you have stated? I don't think the discharge from the softener will hurt your septic system. Some think the salty brine will stop some of the action but most do not. The floor drain has a built in trap and is about the only trapped fixture in the house that doesn't have to be vented,(unless you fall under UPC code) But I'[m n ot really sure what your intensions are. How do you wish to install the floor drain? You said into the 4" Pvc line which would put it under the cement. Did you mean to say stack? Regards, Tom

I mean the vertical pipe is fixed in place, in concrete below and to the walls/plumbing above, so that I cannot cut and spread it apart to glue in a T joint. I hope that makes sense.

And I am not going to do anything with the floor drain. I will instead run the existing 2" PVC pipe higher around the wall and T it into the vertical sewer pipe (at least that si what I am thinking). Like this drawing below.

OK Jeff, I understand. The way I see this going down is to first prop up the PVC stack with a raiser clamp,(see image) and 2 X 4 Jacks cut to size to prevent the stack from falling. Now take a and prime and glue a 6" piece of 4" PVc into a PVC 4 X 2" sanitary tee, (see image) now measure the overall length of the San Tee and make your cut 1/4" longer. Make the cuts straight . And at least 4" off the floor line. You may now take two 4" No-Hub Clamps<(see image) and slip the clamp on first and then roll the rubber gasket down. Fit the tee in and tighten the clamps. The hard part's done.
Now prime and glue a short piece and glue a PVC tee in facing up. A AAV(Air Admittence Vent) (see image) will glue into the tee to vent the 2" "P" trap that you will glue intgo the vent tee. All the remaims is to prime and glue in a 2" street ell and glue the drain line to it. Give the drain line 1/4" to the foot slope back to the trap. That's how I would do it. Good luck and thanks for rating my reply. Tom

Thanks. I think I understand it. The AAV will be inside the basement. Do they work well at keeping out sewer gas order? It would be possible to vent up the basement wall and right angle outside through the wall of the house if that is better, but then I would have a vent in an area where you are always walking by at ground level.. . Does not seem good to me.

And last (I hope) I assume using a saddle T is not a good idea on the 4" stack (something like this one PVC Saddle Tees from the Plumbing Store) instead of cutting it?