DWV vs. PVC vs. ABS

[md2lgyk]

I need to make a small repair to a section of my home's drain piping. The local big box store has tons of DWV fittings but no DWV pipe (or is there such a thing?). Can I use PVC pipe with DWV fittings? And what about ABS? They have no ABS fittings but do have ABS pipe. Can I mix and match these things? Very confusing.

The original piping is 1-1/2 copper, but I don't know if I could find copper fittings that size any more or if I would want to attempt soldering pipes that large.

[LazyPup]

The term "Schedule" followed by a number is referring to the ASTM (American Society Testing Materials) standards for pipe. Primarily it defines the maximum pressure and temperature working load of the pipe determined by the wall thickness.

PVC pressure pipe may range from Sch.20 which is a lightwall low pressure pipe through sch. 200 which is a moderately high pressure pipe.

In residential applications we commonly see sch. 20 through sch. 80. (PVC is only approved for "supply" lines, which is the line from the municipal main to the main water shutoff valve within the structure. PVC may not be used for "distribution" which is the water supply piping within the structure. (CPVC is approved for distribution).

PVC pressure pipe may be used on both pressure and drain applications.

PVC or ABS- DWV (Drain, Waste & Vent)pipe is a thin wall pipe similar to sch. 20 but it may only be used for gravity flow Drain, Waste & Vent applications.

In all cases the pipe is required to have the ASTM certification number and rating printed on the pipe, and when installing the pipe you are required to postion it so that the ratings can be easily seen for inspection. (Pay particular attention to this as many inspectors will "red tag" your job if they can not easily see the specifications).

The codes expressly prohibit directly gluing dissimilar pipe or fittings together (PVC to ABS).

The codes require that you must use an approved primer to clean and prep the pipe before gluing. You will note that the primer is made in both clear and purple dye. The purple dye type is used in new construction or in any application where the job will require inspection so the inspector can insure primer was used. For home repair or DIY projects that will not require inspection you may prefer to use the clear type because the primer is very thin and watery and if you happen to spill any on a finished surface it will instantly make a permanent purple stain.

When selecting Primer and Glue be sure to read the label to insure the product you are getting is listed as approved for the type of pipe you intend to use it on. (Do not trust the clerks in the big box stores because most of them do not know that there is a diffference and if you happen to use the wrong glue on an inspected job you will have to rip it all out and do it over again.)


When examining fittings you will not that PVC pressure fittings will be listed by Schedule (Wall thickness) and all pressure fittings are rated by the degree of bend. I.E. 45 deg, 60deg, 90deg. etc.

In physical appearance PVC pressure fittings have sharp bends on the corners. PVC pressure fittings MAY NOT be used for drain, waste or vent applications because the sharp bends will restrict the flow of gravity pressure waste systems which would cause clogs, and they will not permit a snake to pass through the joint for rodding the line.

DWV fittings are listed by the fraction of a circle (called BENDS) thus a 90 deg angle DWV fitting would be listed as a 1/4 BEND (90 degress is 1/4 of a full circle).

In physical appearance DWV fittings will have a radious curve at all changes of direction to reduce internal friction of flow and permit rodding a line.

You will also find Black ABS pipe and fittings listed for DWV purposes. ABS is made in exactly the same sizes and shapes as PVC DWV pipe and fittings, and either material may be used for the drain, waste and Vent system in a structure, however..

PVC and ABS pipe or fittings may not be intermixed. The code prohibits gluing dissimilar plastics together therefore, when making repairs, whichever material is present in your home must be used to make the repairs.

In cases where availability is a problem the code will permit ONE JOINT to transition from PVC to ABS or vice versa if that transition is made by means of and approved rubber collar coupling (FERNCO). Some local codes will allow ONE direct glue joint to make the transition providing the joint is in an exposed position.

Once the transition from one material to the other is made all additional pipe and fittings must be the new material (ABS or PVC).



PRESSURE FITTINGS

[md2lgyk]

Thanks for the comprehensive reply. One more question: for a sink drain application, is there a particular reason to use a sanitary wye instead of a sanitary tee, or vice versa??

[md2lgyk]

Oops, never mind. Could've answered my own question if I'd bothered to look at all of your excellent illustrations.