Hi, We have a 1999 gulstream sun voyager that has a 6 gal suburban tank. We've been getting only about 2 min of hot water and then its cold. I can hear the tank trying to recover. Is it the thremostat? Or are there heater elements in it like a household heater?
How fast are you drawing out the water? At 3GPM, 6 gallons is gone in 2 minutes. It takes the better part of an hour for most of these units to recover. Your shower head should have a flow restrictor in itthat holds back to a gallon or 2 per minute.
Also, there should be a thermostat on the heater, check the owner's manual. If it is set too cool, you will draw straight hot water for bathing and such. If it is set hotter, you can mix in more cold, but BE CAREFUL! Water above 125 degrees can scald you.
Why not check to see how much you get out of the water heater when you drain it? If you shut off the water supply, create some way to catch the water that comes out and then remove the drain plug and lift the relief valve to allow air to enter the tank. In this way you can see if the tank if full of ...... something other than water. While you could flush it, I would think that if it is so near full as to limit the hot water like that it could be a serious problem.
A couple of questions. When you run out of hot water, does the water heater fire up to try and reheat right away or before you are completely out of water? Could it be that you have a bypass kit installed and that the bypass valve is not completely closed and you are not getting all of the water from the water heater, but perhaps it is coming from the cold supply?
Kirk's reply just reminded me of something I used to run up against when I was repairing household water heaters: single handle faucets. Sometimes the valve assemblies get worn inside and while they don't drip into the sink or tub, they may bypass cold water into the hot pipe and out another faucet. I don't know if you have any of this type of faucet, but it could account for the onset of your problem.
The way to check is to feel (BE CAREFUL, THIS MAY BE VERY HOT!!) the water heater relief valve when the problem occurs. If it's hot, the problem is a cross connection somewhere, if it's cool, the problem is in the heater.
Thanks for the great ideas. We did drain the tank and got about 6 gals out and it looked pretty clean inside.Kirk, I'll try your idea, but our season is almost over up here in Siberia (Adirondack Mount. area in northern NYS). If I don't have to winterize it soon, I'll try your other idea, Kirk.