Robin, there are only three reasons that water doesn't come out of the drain valve on a water heater. Sediment in the bottom, clogging the valve or vacummn on the tank or valve not working. Opening the temperature/pressure relief valve should solve one problem. The other two are harder. But since you have water running out the hose when you open the cold water valve in the bathroom, those aren't your problem. You can change the elements without draining the water. Close all valves, disconnect electricity, lay towels around the bottom of the heater, get new element ready, remove the old element and put in the new one. If you're fast enough you won't make too big a mess. I've done it with no more than one big belch of water coming out. Sometines the elements will be expanded and will want to hang up when coming out. Pull hard, you don't have time to try to save it. But, like BC I would test the elements first. I'm like BC again, I've seen this happen with single handle faucets but not doubles. I'd also like to know what you find when you find it. Interesting problem. Keep them coming.