Can Fire Hydrants Run in Floors (with False Ceilings) Above Cable Trays?

It depends on the local fire code regulations where the building is located.

I suggest you contact the local fire inspector's office and obtain a copy of their fire code restrictions.

Allowed is something that would best to address with local codes. If in fact one of the pipes leak it would usually set off a fire alarm.

"... a walkable false ceiling?"

Isn't that called a floor? From this brief description it sounds like it would interfere with automated fire suppression response.

Not if you are upside down. -- JHF

Sure. Just be sure to install drains in the cable trays so they don't full up with water.

Are you asking if you can install sprinkler heads above cable trays?

What is a "walkable false ceiling"?

His nose runs and his feet smell.

He's built up side-down.

Thanks OS, you described what the OP meant quite nicely. I was struggling with exactly what it was he was asking advice on...

But yeah, access and serviceability make the idea of running these pipes (any pipes) over a cableway undesirable.

Walkable false ceiling is another one....sounds great....most ceilings I encounter after the fact are anything but walkable....no service access consideration at all....and then if you're lucky enough to be onsite during the build and ask for a service gantry/crawl way in the ceiling void the architect doesn't get it.

GA!