Bathroom floor drains for multi-family units…this is totally genius. I can’t even tell you how many times we have had to deal with sloppy showers/tub incidents that inevitably led to water damage in the unit below. (Sure we charge the tenant for this, but I’d rather not to have to deal with the hassle) I get understand the concept to put them in: subfloor, rubber, a layer of mud, tile. But can you retro fit a a bathroom without removing the tub/shower unit?

Has anyone put these into their multi-families, and if so how did you install them? What were your results? Can they be retro fitted?

Sean, whenever we're doing a renovation to one of our bathrooms, we had them along with a trap primer that is feed off of the vanity cold water supply. We've also done them by access the floor from the ceiling below. The issue with going from below is that you can't easily slope the floor above & you can easily install a trap primer. When we do it from below, we use mineral oil in the trap as well as a one-way floor drain seal to help prevent sewer gas from becoming a problem. We also make sure to do a thorough job sealing along the tub, vanity, toilet baseboards to help keep the water contained. Additionally, no matter which method we do, we add a raise threshold.

://www.bing.com/images/search?q=Floor+Drain+Trap+Primer+Diagram&form=RESTAB&first=1

Sean, we've never bothered to put a rubber / pvc / vyinyl / kerdi type of barrier under a readymade tub or shower stall. About the only time we've done that is when we're actually making the shower stall on site.

IMO one of the key requirements for a floor drain to work properly is to use at least 2" pipe, slope the floor towards the drain, seal along the edge of the tub / shower unit, seal around the vanity & base board and to have a threshold that is raised about 1/2". If you do this properly any spills from an overflowing toilet, sink or shower will go down the floor drain & not cause too much of an issue.

Sean, yes depending upon the bed needed to properly set the tile it should be about 1/4" of thin set. We've also used Huber Zipwall as underlayment then treated the seams & fasteners like we do when installing Hardiboard or Durock & coated it with a liquid waterproofing like Red Guard. The method that we use depends upon whether it's for just a shower stall or a whole floor drain system & the skill set of the installer.

I'm presuming that when you mention "rubber" that you are actually referring to PVC pan liner such as the Patey 30 or 40 mil liner. Here's a link to a detail showing PVC liner installed over a bed of sloping mortar with floor tile installed in thin set.