hot water plumbing mystery?

Three possibilities come to mind: First is that the tank is not heating to high even though it may be set to. If you get plenty of hot water elsewhere then this is not the cause. Second, it could be loosing a tremendous amount of heat before it gets to the bathroom, but 30 feet shouldn't loose that much heat. Possible causes can be not so hot water to begin with combined with heat loss through the pipe. But again, I tend to doubt this.

The third possibility can be a mixer valve inside the wall, usually behind the shower control. It's possible that - if you have one - it could be failing and causing cold water to mix in with the hot water thus cooling the output temperature.

To diagnose all three of the problems you need to know first that the tank is properly heating. If not, it can be caused by a faulty thermostat, a faulty gas valve or a ton of sedimentary buildup in the bottom of the tank. Tanks need to be flushed periodically or sediment buildup can cause the tank to work harder to heat the water. And in extreme situations, the water may never heat fully. AND your gas or electric bill would show that right away.

Another thing you need to know for sure is whether there is a mixer valve in the system. If so, whether it's functioning correctly. If you can access the hot water inlet pipe, run the hot water long enough to get hot water at the valve. Then carefully feel the copper pipe to see if it's hot. Almost too hot to touch. If so then you probably have a faulty mixing valve.

As for the other option, heat loss, this isn't something that would develop unless there was a new hole in a wall or an AC line blowing on the pipes. Though rare, it could happen. But if it is recent and there are no structural changes then I'd only look at this as a last option.

If none of this serves to solve the problem then you may have to call a professional. Unless someone here has answered your question and helped you find the problem.

Best of luck with your project.

'')

ADDITIONAL: One more thought came to mind: It's possible that somewhere there's a cross connection between the hot and cold lines. Like possibly a sink faucet that is left on but is shut off at the outlet. Such may be the case with a portable dish washer that connects to the faucet. With the hot and cold valves open it's possible that when the dishwasher is not on, hot and cold water can be passing through into one another. It may be that when you run the hot water in the shower cold water is cross mixing with the hot in that open valve and thus giving you luke warm water. So that makes FOUR possibilities.

Again, best of luck with your project.

'')

how hot is it coming right out of the heater? it doesn't matter the setting if its not heating properly.

second that's a small line so its going to lose heat fast so it needs to be insulated the full way.

last if it is an old heater it might be filled with sediments and sometimes this can block half of the tank and reduce capaicity to 20 gallons. open the flush valve at the bottom of the heater and see what comes out, if its a lot of trash and sediments then the heater needs to be replaced since those sediments are from the tank rusting out.

also there is supposed to be a tube that directs incoming cold water to the bottom of the tank so it doesn't mix with the already heated water going out the hot water line. this tube may be broken or missing.

first thing is make sure you have hot water first then start tracing it back to where it stops being hot

For a half inch pipe running for 30 feet to a shower, you are losing 50% of the heat before it gets to the shower. This run is far too long. You are far better off installing an Electric shower which heats the water straight of the cold main supply. Even with pipe insulation it wouldn't help much to solve this problem

Check you sink faucet in the bathroom. Is the hot water hotter than the shower? If so, the shower valve is bad.

Sounds like your dip tube is either cracked or broken. Remove nipple from cold side hwh. there is a tube with a flange on it to keep it from falling into tank.Use needle nose to snatch that. pull it out and verify o.k.

tank not heating enough