Washer drain into water tank floor drain

[sheesh1982]

Is it OK to connect the washer's drain into the floor drain of the hot water tank?

 

[frodo]

if you have a regular floor drain then no.
it has to drain into a hub drain or a floor sink
because of the splattering and mess it will make

 

[Diehard]

The hose must also be arranged to prevent siphoning.

 

[frodo]

the hose has to be installed above the water level of the washer
if not, the water will drain out of the hose

then the hose goes into a stand pipe that can be piped to a floor sink or hub drain

 

[Diehard]

Yup ...that will do it!
The OP must understand that the Air Break provided by that standpipe is important.