the valve location depends on the trailer, on my 2011 TH it was under the bathroom sink. In the 2012 model I have its under the kitchen sink. There was a post on here a few days back with the improved valve linked to a Home Depot site. I think I'll get it on order or pick one up as Ive noticed the smell already in this trailer however its getting 100+ out and dumping the gray tanks every few days helps and I put a odor tablet in the gray tanks also. If its the black tanks I read on the odor bottle to add two if needed due to heat.