Circular outlets are also manufactured with a smooth flange for bonding, adhesion or mechanical fixing.

Although not giving the "over and under" bond of the perforated range, these outlets can be secured into a circular drainage hole. The spigot is 240mm long and is inserted down inside of the HDPE drainpipe. This gives ample assurance that no water can back up behind the rubber and onto the deck. The spigot is slightly cone shaped and ribbed. This helps with installation into the hole, and prevents water passing back up behind the spigot.

Installation
Waterproof the area around the drainage hole. This can be done either by installing a patch around the area or by waterproofing the entire deck in the normal manner. Insert the correct size of outlet connector into the hole so that it is covering the waterproof membrane. Secure the connector either by using fixings or adhesive.

Then prepare the area for another layer of waterproofing membrane so that the outlet connector is encapsulated in a "sandwich". To ensure that the second coat of waterproofing bonds properly, the area should be primed. Here a patch of the same type of membrane is installed and adhered across the face of the outlet connector, completely covering the flange and bonding to both it and the first layer of waterproofing membrane beneath.

By doing this the water cannot get behind any parts of the connector and enter the structure. Once the membrane / adhesive is cured a hole may need to be cut to reveal the drain pipe, and a leaf guard or gravel excluder is inserted into the hole. The outlet is then finished. Above is an example of the circular outlet with a smooth flange, where the surround is bonded to the waterproofing membrane.