Primary And Secondary Roof Drains

Secondary drainage to pour over top of outlet box if primary clogs.

Primary and secondary roof drains.

It is very important not to place secondary drains in any kind of sumps. Where should the secondary drainage be discharged. Where primary and secondary roof drains are manufactured as a single assembly the inlet and outlet for each drain shall be independent. The better choice if it can be accommodated is one of the first two methods where overflow at the exterior of the building roof is provided without the need for secondary drainage piping.

Providing an immediately adjacent secondary overflow drain next to every primary drain with a separate piping system. The secondary system ensures that if the primary system or primary drains are plugged or overloaded the secondary system will handle the rainwater and drain it away protecting the building and its occupants from harm see figure b. Where roof drains are required secondary emergency overflow roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that water will be entrapped if the primary drains allow buildup for any reason. The patented froet drain is an innovative drain product created to solve the dual drain requirement for overflow protection.

If the sump is 2 or deeper the secondary drain shall serve as the primary drain totally defeating its purpose. A secondary drain placed in a sump will start working as soon as water reaches the top of the standpipe. The upc also allows for secondary and primary drainage to be combined provided the rainfall rate utilized is doubled and that the secondary drainage ties into the primary drain downstream of the last horizontal offset. If the sump is shallower than 2 it will be full of standing water which may freeze and damage the drain and the adjacent roofing.