I've installed a shower pan in a second flore area and figured I would trap the 2" line just under the 4" thick floor. So the distance from the floor above to the bottome of the trap would be about 7". Is that enough of a column of water to force water through the trap?

Hi Vonkopan

If the shower drain is vented and the 2" ptrap fits in the space and connects to the shower properly then you will be just fine with the 7"... ;)

Mark