Adapting PVC Vent Terminations

When non-standard plastic PVC pipe is used in a ventilation or drainage application, it may be necessary to adapt to a standard termination to allow for the use of a vent screen insert or cap. In some cases, adapting a termination may also correct deficiencies found in an existing installation. Because an adapter is often more cost effective then designing and manufacturing a custom vent screen, we will discuss some common solutions to easily convert uncommon vent terminations below.

Adapting a Hub to Street Termination

As noted on our vent hub termination page, not all elbows are created equal. Our PVS series vent screens are designed to fit inside standard PVC hub to hub elbows. Hub to street elbows are similar in design, though the hub end is often cement welded to the straight length of PVC pipe and the opposite “street” side is the same diameter as straight PVC pipe (pictured below). The most common and cost effective solution to this problem is to slide an inexpensive coupling over the existing street termination so that the appropriate PVS series vent screen may be used. If the outside diameter of the elbow termination is 2-3/8″, then a 2″ coupling may be used for proper PVS-IS2 and PVS-RS2 fitment. If the outside diameter of the elbow termination is 3-1/2″, then a 3″ coupling may be used so that the PVS-IS3 and PVS-RS3 vent screens may be installed.

Vent Termination Hubs Compared

The picture below is what the 2″ hub to street elbow pictured above looks like when it has been adapted with an inexpensive $0.50 2″ coupling. Since couplings are tapered on the inside, it can be slipped on tightly without the need for any adhesives, cement welds or tools. Hub to street elbows are one of the most common vent termination sizing problems encountered in the field and the simplest to correct.

Adapted 2" PVC Hub X Street Vent Termination

Important Considerations When Changing Vent Termination Sizes

When adapting a vent termination to a different size is required, it is important to always adapt to the next larger size. Adapting to a smaller termination would introduce an unnecessary and potentially unsafe restriction within the ventilation system. This same principal applies to drainage applications as well, since reducing the termination diameter would restrict the flow of water. Please remember that adapting a vent does add to its length, so it is also important to make sure all adapted vents are a minimum of one foot above the snow line. The snow line is the expected maximum height of accumulated snow.

2-1/2" to 3" Vent Hub Adapter

Adapting a 2-1/2″ (2.5″) Vent to a Standard 3″ PVC Termination

In the image to the right, a straight 2-1/2″ PVC pipe has been terminated with an affordable 2-1/2″ to 3″ PVC adapter coupling. 2-1/2″ straight PVC pipe has an outside diameter of 2-7/8″, which the pictured adapter is designed to fit. When this adapter is installed, the PVS-IS3 and PVS-RS3 vent screens may be used to protect the vent. Customers that have an existing 2-1/2″ hub to hub adapter terminating their vent may find it necessary to remove it by sawing the adapter off to expose the straight pipe. Another option to convert the 2-1/2″ hub to 3″ is to use a short length of 2-1/2″ PVC pipe that inserts into the existing hub and into the 3″ adapter. Please note 2-1/2″ PVC pipe is not ordinarily used in residential ventilation applications. Because of this, locating 2-1/2″ PVC pipe and fittings at local big box hardware stores is difficult and often requires a special order or online purchase. However, local plumbing supply houses often have lengths of 2-1/2″ PVC pipe and adapters in stock.

Converting a 1-1/4″ (1.25″) Vent Termination to 2″

On occasion some of our customers will find the need to convert a 1-1/4″ vent termination to a standard 2″ hub termination. This is easily accomplished with an inexpensive 1-1/4″ to 2″ PVC adapter coupling. Since 1-1/4″ PVC is rarely used for ventilation, these adapters are difficult to find in big box hardware stores and often require they be purchased online or from a local plumbing supply house. Since 1-1/4″ to 2″ PVC adapter couplings are designed to fit over straight pipe, an existing hub would either need to be removed or joined with an adapter using a short section of 1-1/4″ PVC pipe. Once the adapter has been installed, the PVS-IS2 and PVS-RS2 vent screens may be used to protect the vent.

Converting a 1″ Vent Termination to 2″

Though 1″ PVC pipe is rarely used for ventilation applications, there may be a need for some to protect a 1″ termination with a screen. 1″ to 2″ PVC adapter couplings are available to accomplish this task. The 1″ to 2″ adapter coupling will simply slip onto a straight length of 1″ PVC allowing the PVS-IS2 and PVS-RS2 vent screens to be used. Since an existing hub on the 1″ pipe would interfere with an adapter coupling, it must either be removed or joined to the new adapter coupling with a short length of 1″ pipe.

Additional Assistance

While converting most vent and drain terminations is an easy task, we understand those not familiar with the process may need additional assistance. Whether it be locating the adapters or application specific tips, we encourage our visitors to contact us for additional information.


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