Most Common Point of Failure
Weakest Point In A Shower Pan Hot Mop
You can hire the best hot mopper but if your drain fails it will appear as if the shower pan hot mop has failed. The shower drain is the single most common point of failure in shower pans during a flood test.
The hot mop layers are laid in between the two bolting flanges on the drain assembly. If there is an issue with these bolting-flanges any water that comes up from below the drain could get in between the flanges and under the hot mop.
Trying to reuse an old drain assembly comes with a much risk of issues with the bolting flanges. We always HIGHLY recommend installing a new drain assembly that has both flanges (top and bottom) new.
Nonetheless, even some new drains have issues. In order to prevent water from getting in between the flanges we (the hot moppers) have to tighten the bolts with enough compression. If the drain subflange has weak threading or threading anchors then the bolts will keep spinning and not provide adequate compression for a flood test. If this happens during the final stages of the hot mop then the drain may need to be changed out.
It is best to choose a drain that has heavy duty bolts for compression and that attaches to the pipe securely. Drains that have cast iron (metal) subflanges (bottom plate) and/or bolt threading have less issues with the bolts stripping. However, these drains are usually "slip-on" and have a compression fitting for attachment to the drain pipe. This compression fitting is often left too loose and can leak around the outside of the pipe. A good effort needs to be made to attach these metal drain bottoms securely to the pipe and test them by pulling on them to make sure they don't slip off easily.
If you are uncertain you can send our office pictures and we can give you feedback on the drain.