where to tie in drainage for my basement sink

Hi,
I need some advice on where I can tie into drainage for a new sink I will install in my basement.
I have three 4 inch pipe openings with caps on them in my basement floor. One of the cap is installed at a slant which I'm guessing is the clean out. The other 2 are installed vertically straight up. When I open up the vertically straight up caps, one of these have water filled about half way up. The other does not have water in it and bends at about a 45 degrees down. I tested both of them by pouring water into them and they both drain fine. I did another test where I turned on the tap of a sink on the main floor and I can hear water flowing from the opening that has the 45 degree bend. The house was built in 1975. Which of these can I tie my drainage into for my basement sink? Thanks.

Br code, none of them, unless the center one is an unused floor drain. By code, you cannot use a cleanout, which the two outer plugs are, for a drainage connection.

hj said:

Br code, none of them, unless the center one is an unused floor drain. By code, you cannot use a cleanout, which the two outer plugs are, for a drainage connection.

Click to expand...

Thanks for your reply. Can I tie into the floor drain (without the square box in the picture) for draining the basement sink?

You can let the water run across the floor and into the floor drain if you really wanted to.

A floor drain has a trap under the floor, so you cannot properly plumb a sink into a floor drain.

The only correct way to do it will be to break some concrete so you can get to the drain pipe and install a wye in the line for a new drain.

Your new sink trap will also need a vent.

cacher_chick said:

You can let the water run across the floor and into the floor drain if you really wanted to.

A floor drain has a trap under the floor, so you cannot properly plumb a sink into a floor drain.

The only correct way to do it will be to break some concrete so you can get to the drain pipe and install a wye in the line for a new drain.

Your new sink trap will also need a vent.

Click to expand...

Would it be OK to break up the concrete and install a T to connect into the floor drain pipe to tie into the sink. This way I can tie in the sink and keep the floor drain open as it is now. The floor drain is 4". There's already a rough in vent that will be used for the sink.

The proper fitting is a wye, and it must be downstream of the connection for the floor drain. The pipe for the floor drain is not very likely to be 4", and tying into the floor drain line could lead to the new sink siphoning the trap of the floor drain. Most places would now require the floor drain to have a vent also.

n2r88 said:

Would it be OK to break up the concrete and install a T to connect into the floor drain pipe to tie into the sink. This way I can tie in the sink and keep the floor drain open as it is now. The floor drain is 4". There's already a rough in vent that will be used for the sink.

Click to expand...

no - you need to break up the floor and tie into your main line somewhere - and must vent your new drain for sink

hj said:

Br code, none of them, unless the center one is an unused floor drain. By code, you cannot use a cleanout, which the two outer plugs are, for a drainage connection.

Click to expand...

The center one was capped off with plywood cover on top of the box before I took it off to have a look. Does this make it unused and therefore I can install a T to tie into it for the sink. Just want to know all my options before I choose my course of action.

Without knowing how the underlaying lines are connected, there is no proper way to answer that question.