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Waste line connections

Posted by t20sl (My Page) on
Sun, Jun 6, 10 at 10:06

Currently I have 1 toilet but am moving it a little and adding a 1/2 bath. I have a vertical waste line in basement 3" diameter. It is connected with a 1/4 bend to current toilet horizontal of about 5 feet. I am remodeling and have to move current toilet over by one floor joist. I was going to use either 2 wyes in vertical or combination wyes depending on how dimensions work out. I have read that wyes or combination wyes are not allowed in vertical waste stack. Is this correct? If so why is this?

Follow-Up Postings:

RE: Waste line connections

Fixture arms MUST BE connected to a vertical stack by means of a Sani-Tee.

In all cases, whether the fixture arm is connected to a vertical or horizontal line the bottom of the pipe at the trap weir may not be higher than the top of the pipe at the vent opening.Some months ago I prepared the attached illustration on this subject.

It should also be noted that while the codes define the maximum length of a fixture arm when installed with a 1/4" per foot pitch, if the pitch is increased, the allowable length would be shortened.

Section B shows the correct method of connecting a fixture arm while section C illustrates why we may not use a Wye or Combo.


RE: Waste line connections

Ok. If I vent the waste line immediately after the closet bend can I then use a combo wye or wye? The original copper had a vent at wall junction (had a wall hung toilet which I am changing to floor mount) and ran hortizontal to 90 degree downward bend to waste stack. Stack had no vent and had a lavatory and washer connected with wyes. Both lav and washer had vents to roof, alonf with the toilet vent.

RE: Waste line connections

If you install a vent on the horizontal line between the closet bend and the stack, the section of line from the closet bend to the vent is defined as the fixture arm, but all line downstream from the vent would then be classified as a vented branch and a vented branch.

You would need to check your local code. Some jurisdictions will allow a vented branch to be attached to a vertical stack by means of a wye & 1/8 bend or combo while other jurisdictions strictly prohibit any wye's on a vertical stack.

However, if you do attach an auxiliary vent, the vent MUST RISE vertical until it reaches an elevation which is 6" higher than the flood level rim of the highest fixture served by that vent before it can be turned horizontal.

As you can see in the attached illustration, if the water closet is the only fixture served by the vent, the vent would need to rise vertical until it reaches an elevation at least 6" higher than the rim of the water closet bowl. If that horizontal line was also serving a lavatory the vent would have to rise 6" higher than the lavatory bowl rim before you could turn horizontal.


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