I want to put a toilet, sink and shower in the basement. My question I have is I have a 5 or 6 inch pipe behind my washer with a screw on cap. It is a drain of for the kitchen sink and washer. Can I connect a toilet to this pipe.

I would not recommend it. Without seeing it, it sounds like you are describing a grease trap for your kitchen sink. Connecting new piping to old always seems like an easy task in planning, but before you spend the time and money on a new bathroom I would recommend a camera service from a reputable company to be sure your sewer is in good condition for the remodeling and get a layout of the piping. Too often I have seen bathrooms added to bad sewers and in a short period all of the new work needs to be ripped out to fix the sewer. This also applies to expensive landscaping, concrete patios/driveways, decks and pools. Knowing where your sewer is and what condition it's in can save you a lot of money and headaches in the future.

Hi Cimco...

If you aren't having issues with the drain I'd wait on sending a camera down as pghplumber recommended above, OK? Here, in most cases with pipes as large as you describe, if you aren't having any issues then I wouldn't worry about issues down the road quite yet! Unless you have extra money, of course, and then it can't be a totally bad idea... I guess!

It sounds like you may have a 4" cast iron drain pipe behind the washing machine and you are asking about connecting into the CLEAN OUT fitting via the threads for the clean out cap... right?

In most cases, connecting into a cleanout is a problem because the cleanout fitting lacks direction like other drainage fittings. This means that waste water from above can very easily flow into the new piping and that would certainly lead to issues as things started hanging up on the cleanout threads as well.

Also note that you would probably have to build the floor up say 10" (or more) or so to accommodate the height needed to install a 90 degree fitting for the toilet AND a properly oriented VENT fitting for the toilet/sink. Here, the toilet vent fitting would need to roll above the centerline of the toilet drain and that will add more height to the floor.

Your best bet here will probably be to consider installing a sewage ejector pump or a macerator pump toilet... both types very reliable.

Check them out at:

Zoeller Corporation

Saniflo macerating and gray water pumping systems

Let us know if you have questions, OK?

Mark

Now that massplumber put it in perspective it makes sense. For some reason I mentally picture the "5 or 6 inch pipe with a screw in cap" being in the horizontal position as you may find with old grease traps for kitchens. Sorry for any confusion cimco.
The only other reply that I have is that I repeat the reasons that I cited earlier for a camera inspection. An ounce of prevention... if you are willing to pay for it.

After measuring the pipe it is 4 inch and not case iron. PVC pipe.I think it is a grease trap and will get a plumper in to see. I do have another pipe coming down from upstairs washroom which is about 10 feet away from washer on the same wall.

Is there a test tee fitting like in the below images (see images), or something similar to a grease trap like in the last image below?

Let us know...

Mark

It is more like the first picture but screw on lid on top. And side of pipe as smaller pipes going in to pipe for washer drain off.