Hot water heater - very low water pressure

[Hoklai]

I am having problems with my gas hot water heater. A few months ago it worked fine. Now, whenever I turn on the hot water, it starts out with good pressure but immediately drops off to a trickle. The cold water pressure has remained unchanged. I have checked the thermostat vs. the actual water temperature and it heats to the correct temperature (I checked the temp at both the 120 and 130 degree setting). The water line into the heater has an on/off valve and I have opened and closed it a few times as well. The water is not discolored or smelly. I've even flushed it recently, and not much of anything came out in the drained water. Any ideas? thanx

[Joseph Meehan]

I have no idea exactly what, but I would be looking for some obstruction going into the heater. A partly closed valve or a malfunctioning pressure control device.

[PhotoMan]

Perhaps you need a cold water heater ;-)

[HeatMan]

You need to check the fill valve on the cold side.

[Terry]

One possibility; valve on inlet or outlet might have lost its washer (and screw) if of that type, which has fallen into the seat of the valve or washed away into the pipe, partially blocking it? Happened to main water valve here; we replaced the main shut of with gate valve/s. Many years later we discovered some bits and the screw of the original shut off in other parts of system partially obstructing it! Good luck.

[HeatMan]

Gate valves suck. Use ball valves. One quarter turn and they're closed. You can use a ball valve to throttle (slow down or modulate) the water flow, but not with a gate valve. A gate valve is open or shut only. And if the gate breaks off, you're screwed. (It's happened to me)

[neil]

water

We had the same problem and it turned out to be a cheap washer in the tap that expanded when heated, so as the water got hotter, the flow was diminished. neil