We have no hot water pressure through out our house,but we do have cold water pressure. It takes 40 minutes to run enough water to to bathe then by the time that's done the water in the tub is cold.We have a gas water heater. PLEASE HELP!!

Does your water heater have Heat Trap Nipples, (see image) you'll find them coming out of the tank. Let me know. Tom

Is this electric or gas water heater? Have you confirmed that the tank is actually filled with hot water. Tell us more because this could be a stat, bad element, pilot light, or the heat traps. We can't tell yet but we will figure it out. Open the drain spigot on the heater: get real hot water under very good pressure?

It si a gas water heater... speedball1 no I do not have heat trap nipples

Open the darin spigot and test the water temp. If below 120 raise the stat to HIGH. We must first establish that you even have hot water in the heater. Plugged mixing valves can cause problems but you have this issue every where, right?