Hello
I am installing a new basement 2" floor drain to handle condensation from a new A/C installation and hot water tank high pressure relief tube. I have a constructed basement floor. The height difference between the floor surface and the horizontal 4" DWC running below is about 20" at the point where I want to tie in. The new drain will have a 2" P-trap higher than the main and it's output will travel about 24" horizontally over to the main.
1. My question is at what angle I should enter the main? My original plan was to place a "Y" such that the feed from the P-trap would enter the main from the top. The alternatives might be to enter 45 dgrees from vertical or to just come in horizontally.What is best practice in this situation?
Another concern is that water in the P-trap might evaporate and allow sewers gases to come up through the P-trap into the basement. We use A/C only in summer here in Colorado and the average humidity is very low 10-15%.
2. I have examined another floor drain installed by the builder. The connection to the main is horizontal - straight out from the side - and the P-trap starts there and goes down below the main before turning vertical up to the floor drain. Doesn't this fill the P-trap with waste water? This floor drain is just emergency for any overflow from a washer.
Any thoughts?

Hey Ken,

I have a constructed basement floor. The height difference between the floor surface and the horizontal 4" DWC running below is about 20" at the point where I want to tie in By "constructed basement floor" are you referring to a poured cement slab and what's a DWC? Please explain. Are you saying that the house main,( is this the 4" DWC?) is 20 inches below the slab? Let me know.

Another concern is that water in the P-trap might evaporate and allow sewers gases to come up through the P-trap into the basement. We use A/C only in summer here in Colorado and the average humidity is very low 10-15%.
I know. My daughter lives in Denver. They sell a "Trap Primer",(see image) from 40 bucks on up to meter water into the trap.
Please let me know the elevation between the house main and the slab. Regards, Tom

Tom,
Thanks for the reply. Sorry, I meant DWV not DWC. A constructed floor is made by laying joists and putting down tongue and groove OSB. Here in CO we have to run fresh air under the floor so it is completely sealed at all floor panel joints and around all pipes and around the perimeter of the basement floor where it meets the foundation wall. A fan pulls air through an inlet on one corner and exhaust outside at the other corner. Same as treating radon.

Well, the primer was totally new to me - thanks a lot for that one!

The other issue has to do with attachment of the drain to the main DWV (3"). I put it vertical this morning i.e. straight down into the main DWV pipe. I saw another drain installed by the builder where he put it into the side. So I am guessing any waste water that comes down the main, some may go through the T into the p-trap of the drain. There is only the normal 1/4" per foot pitch on the floor drain pipe into the main. I haven't smelled anything in the last 10-years but it doesn't sound like the right way to tie into the main.

Thanks again for the answers!
Ken

I put it vertical this morning i.e. straight down into the main DWV pipe. You put a 90 on the tail of the floor drain and simply dropped straight down to connect to the main?
One more time ,Please let me know the elevation between the house main and the slab. Is it 20 inches down? Let me know. Tom

Tom,

Thanks again for the reply! The floor is not a slab but as I described in my last - it is wood/OSB over engineered joists. The distance from the floor down to the top surface of the main is 20".

The floor drain system is 2" DWV/ABS which is allowed by local code into existing ABS systems. I came off the drain tail into a P-trap then over to the main with a 1/4"/foot pitch and into a long throw 90 degree elbow and into the top of the main. The bottom of the P-trap turned out to be about 2" higher than the top of the main waste pipe.

I mentioned the other drain across the room which the builder's plumber installed. He came off the side of the main and into a P-trap then up through the tail to the surface drain. This was originally done for the condensation from the gas furnace/A/C unit. But I long ago rerouted these drain pipes into an existing sink as I knew I would be moving my furnace eventually and the pipes used to run across the floor for 3' which was a hazzrd. This drain has not been used for years. Point is, there is water in the P-trap and the only way it could get there is from the waste main - yuck. I intend to cut out the floor and remove it.

Anyway, is there anything you see that I may not have done correctly?

Ken

For a 20" spread I would cock a wye or combination wye and eighth bend up on a 45 degree off the nnain and raise up where I would leve everything off with a eighth bend and tie it into the tail of the floor drain observing the 1/4" to the foot slope. Good luck, Tom