Drainage Fixture Units

@coachadamcoers What is the drainage fixture unit for a mop sink per IPC Table 709? Is it considered a service sink (2 dFU) or a floor sink? If it’s a floor sink, what does the table mean by “see note h?”

This can be confusing at times. a mop sink should be considered as a service sink that is floor mounted.
A floor sink, however, is a recessed space in the floor which serves as an indirect drain for a plumbing fixture such as a sink - these are oftentimes used in commercial applications in lieu of a p-trap as the floor sink will have a strainer which can capture any obstructions and allow for easy cleanouts vs a p-trap buried under the floor - which is why the dFU for the floor sink says note H.

what note H and the subsequent 709.4 and 709.4.1 are taking into account is the item which is draining into said floor sink. this is due to the common practice of using these as an indirect waste receptor in lieu of a more traditional P-trap. These notes are saying that the floor sink needs to be able to handle the load of all items draining into it to ensure adequate drainage for the system.

hope this helps!

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