Has any body installed conduits in commercial
fountains and if they have what conduit and
connectors do you use.

Thx

Are you talking about an existing fountain or new construction? If existing, try to keep the conduit out of the water, usually the fountain water is treated with chemicals to inhibit growth etc. No telling what this may do to your raceway. If new construction, no reason you couldnt run PVC in the slab, I dont think a fountain would be under section 68, even if it is accessible to the public. Best to check with your AHJ to be sure.

The conduit is new and has to be in the water
.The manufacturer tells me that I have to use brass pipe(plumbers pipe)which is very expensive.

You must treat any fountain where it is even remotely possible for a person to get in as a section 68 installation. I don't know of any Brass raceways for a part 1 installation approved for electrical so you will probably require some documentation on the raceway or get a site approval from CSA, ULC, Warnock Hearsey, etc.

section 68 is pretty clear on what it covers. This may fall under "decorative pool" but the dimensions have to larger than 1.5m in any direction. 68-100 does refer to copper rigid conduit and PVC. I have never seen rigid copper, as for PVC you may have to check with Scepter or one of the other manufacturers for approval documentation.