No hot water pressure in the house!

Hi y'all,

I've got a 3 year old hot water tank and I also have a pressure relief valve at the water meter. I'm on city water. Here's the problem: I've got no hot water pressure at any tap in the house. Over the past few months, it's gotten lower and lower.
Here's what I've done so far: I drained the water tank to see if there was any sediment in there. There wasn't. I'm in the process of refilling it. There seems to be a little bit of an improvement, but not much. Is it possible there's a blockage in the exit line coming from the hot water tank? I've increased the pressure in the house by adjusting the pressure relief valve.
The hot water line feels hot coming off the tank but once it gets about 4 feet away from the tank, the line is cool to the touch.
What should I be looking for at this point?

Thanks In Advance,

Jeff

Not to nitpick, but a couple of things need to be clarified. The device you refer to as a "Pressure Relief Valve", is a Pressure Regulator Valve. These are used when the main water supply is excessively high. The use one requires an expansion tank between the PRV and water heater. Now, more to the point of your question, I believe if you were to check the pressure of the hot water, you would find it would be the same as the cold. What you are experiencing is a lack of flow. Don't feel too bad, many people refer to low flow as low pressure. Since you indicate that the cold water flow is normal, your premise of a blockage somewhere in the hot water line appears valid. It almost has to be somewhere between the tee from the supply line to the tank and the line from the tank to the house. I would suspect something like a washer in a flex line or other connection using a gasket connection. You should not mess with the PRV without a gauge and then the expansion tank air pressure should be adjust to about the same or slightly less than the PRV.

Ok, yep, I can go along with the idea that it's low flow. And yes, I see it's called a pressure regulator valve. My mistake.
As far as the low flow, I don't think it's on the side where the cold water flows into the tank. That side seems to be running pretty well. On the other side, the hot water side, there are no flex lines. There only seems to be some shutoffs along the way. Is it possible that those have broken down internally? Also, I have no expansion tank, just the PRV. I've checked the flow at a bibb in the garage and it's at 60psi.
I'll post some pics of the lines to see if that would help explain myself a little better.

Thanks.

Could be several things...if there are heat traps, depending on the type, some have a plastic ball that either sinks or floats to close it off with no flow to keep from convection losses in the pipes. SOmetimes, the ball becomes trapped, reducing flow. If there is a galvanized nipple at the tank, and you have agressive water, eventually, that will rust. It could be that it is rusted nearly closed. If you have a non-ball valve shutoff, it could be reducing the water flow if the washer has deteriorated or, if a gate valve, the gate has broken off.

WIth a PRV (pressure reduction valve), you need to install an expansion tank on the cold inlet between the WH tank and the incoming shutoff valve to it. If you don't, after hot water use, the pressure will rise and you could get leaks or the relief valve opening. It's bad on hoses too. Liquids don't compress, so any thermal expansion means the pressure will go up unless there is somewhere for it to go (i.e., into the expansion tank, or maybe blowup a hose like a balloon, or leak somewhere).

OK, this is off the immediate topic of your problem, but I want to address the issue of the expansion tank. Unless you have a PRV with a built-in bypass feature, you have what is called a "closed system". This means that when your water heater heats water expansion occurs. This expansion can be dealt with in one of two ways. First, in an "open system", the expansion is absorbed by the city water main, so you have no problem. A PRV usually creates a closed system. Usually because there are some PRVs that have a built-in bypass that allows the expansion to be absorbed by the main, so again no problem. However, in the majority of the cases, the PRV prevents this from happening. This means that the expansion has to somehow be absorbed within your own plumbing. What happens is the pressure within the water heat rises until the limit of the T/P valve on the tank is reached (150 psi) and the T/P trips to relieve the pressure and prevent the tank from a violent explosion, and yes, I mean a big time violent explosion! That's why an expansion tank is required in a closed system. I sounds like you have not had this problem...yet, but I would have a serious look at the system and consider adding the expansion tank.

I wonder is there is an obstruction in or under the inlet nipple on the tank? I would suggest you also check the valve(s) careful to see if the are defective. I would not hesitate in replacing them with ball valves as they are far superior to gate valves. That's assuming you have gate valves of course. There has to be an obstruction somewhere

Well, Jim beat me to get his reply in. Glad to say we really are on the same page.

A bypass on a PRV only opens when the pressure IN the house exceeds the pressure OUTSIDE the house. Depending on what that is, it could still cause problems, and the code doesn't make a distinction, from what I've been told. And, that assumes it works...

Read this thread, Jeff:

Low hot water pressure