We have a industrial dishwasher in our kitchen of our daycare center. The pipe that sticks out of the floor that the water drains into keeps backing up, why?

Without a picture it's hard to tell what the pipe is other than a drain. If the pipe is only 1.5" and partially clogged, the volume of water from the DW is overcoming the flowing capacity. Can you see below the floor? Is this pipe connected to a larger drain pipe? I'd probably just try to auger out the drain pipe and see what you find.

The drain pipe from the diswasher is a copper piping that leads to a pvc pipe that sticks out of the kitchen floor

The dishwasher has copper piping that drains into a pvc pipe that sticks out of the kitchen floor. The pipe from the kitchen floor is what is backing up and spews stuff all over the floor.

My suggestion is still the same. Too much volume for the flow capacity.

How do I fix the pvc pipe from backing up

The dishwasher has been in place for over ten years now. We never had a problem with the flow capacity before. The pvc piping is about four inches in diameter.

Sounds like an INDIRECT DRAIN connection that goes to a PTRAP underground... required for all commercial dishwasher drains that CANNOT be connected directly to the sewer system.

Here, it sounds like the drain is partially clogged. If you are lucky you will find a cleanout somewhere nearby... maybe in the drain vent... and you can snake the drain through the cleanout. Otherwise, you'll need to snake through the indirect drain/PTRAP and clean the drain to fix this... ;)

I have attached a picture showing one type of setup for a commercial dishwasher indirect connection... can also just be a pipe stubbed above the floor accepting waste from the copper drain.

Questions? Let me know, OK?

Mark

Mark is right, snake it and you should be fine. But not knowing your location exactly you may have a local code requiring a grease trap on all drains in a commercial kitchen, if that is the case the trap will have to be pumped to restore proper drain flow.

Maybe you never had a clog before. You're lucky.