I have a Seward s 600 hot water heater with rear heat exchanger . Last year I installed a by pass valve so that I wouldn't have to put the "pink stuff" in my hot water heater and just drain it to winterize. This year when I went to drain the tank I only got out about a pint of water. It's a six gallon tank so I would assume that there is more in there than a pint. My process was to turn off the water pump, open the hot water faucets- attach hose to my hot water heater's drain valve , open the drain valve and use a drill pump to get the water out but other than the aforementioned pint nothing else came out. I removed the hose from the drain valve and still nothing came out. I tried some other combinations of closing the faucets , turning the pump on etc but nothing- I'm stumped any thoughts ? Thanks