When getting ready to winterize our boat I took the hose off the cold water inlet and water flowed from the inlet. Is this OK? I've winterized for four years by connecting cold and hot water hoses, and this has never happened, but in those previous years I may have turned off the pump and drained the hot water heater first, so that by the time I unhooked the cold water hose there was nothing left to spurt out. When the water started I thought that I had bumped the temp release valve so I pulled it out straight for just a moment, then back. (I shouldn't have done this!) I've ordered another from Seaward. So is everything OK?
I don't think you have damaged the pressure relief valve. If they didn't want it to be used there would not be a handle on it. The valve can also be found at most RV parts stores, if you have one near you it saves a bit on cost and shipping.
You probably just had some water left in the tank when you disconnected the hose. You can make sure it is empty by closing all the faucets except one hot, blow into the faucet water outlet. If you get a few spashes and air out of the tank it is empty, if you get a stream of water, keep blowing until it stops. You can also use an air compresser attached to one of the hot water hoses going to a faucet.
Kerk : The pressuer relief valve should be OK, if the gasket reseated. Some times the old gaskets will not reseal.
Use your shop vac and suck the water out of the heater(open one of the hot water faucets).