What a welcome into home ownership...

Hey there everyone! I have quite the debacle on my hands here.

My wife and I are first time home buyers and have been busy with the new place. We knew it was kind of a fixer upper nothing too severe that we couldn't handle. Till we realized we had no hot water. I had my brother in law test the elements on the old water heater and the lower element was malfunctioning. Seeing that we didn't know how old the water heater was and new ones aren't too expensive we went and a new one(its an electric water heater by the way). And here's where everything gets weird.

The water heater itself is in our master bathroom. That portion of the house, den, master bedroom and bath USED to be part of the garage which would explain why its back there. So anyway I turn the breaker off and hook a hose up to start draining the tank and I go to shut the water coming into the water heater. After I do that I come out to the living room and I'm hearing water like someone turned a faucet on. We have a second bathroom which has a rusted valve to the toilet so it's out of commission for now. But I don't see any water coming out of any faucet or shower. No activity in the toilet. I can feel the water in the valves though especially the shower. I look outside and the outside faucet is dry. We open of the crawl space and look around and the main line is really close to the hatch. Look under towards the second bathroom...nothing. I don't see or hear water dripping at all. And we monitor this till we put the new water heater in. We ended up going out to the street and shut the water off from there. For fear of pressure building up. Anyway we get the new water heater in and turn the water back on at the street and the water heater. And the rushing water stops. The water heater works but our water is still just warm. But it gets hot when I'm taking a shower and my wife turns on a faucet. So turning the temp up on the water heater is not really a concern at least to me in my eyes unless told otherwise. So I start checking else where in the house to see how long it takes for the water to heat up and it's about the same. Almost a minute. I would think it'd be a lot faster seeing as it's a new water heater. So anyway. I turn the faucet on in the second bathroom and the hot water takes about the same amount of time to heat up. but after about a minute or so the pressure drops down to if the faucet was opened a 1/4 of a turn. I don't know what's going on. All I know is:

A.) Our master bathroom works fine, aside from the temperature which could be hotter but as described I don't think it's a thermostat issue

B.) Washer works fine.

C.) Kitchen sink and dishwasher work fine, also aside from temperature which could be hotter but as described I don't think it's a thermostat issue

D.) Second bathroom is messed up somehow.

I know little to nothing about plumbing and being a first time homeowner I'm looking for advice from anywhere. My uncle works at a hardware store and the guy that runs the plumbing department was or is a plumber and I will be going there to pick his brain as well. But I would VERY MUCH appreciate any help that you folks on here could give me. Please?

What should I do? Hiring a plumber is my last resort and I'd like to do this myself if possible.

You may want to turn everything off in the home, and then check the meter to see if there is any movement of the numbers. Sometimes there is a little dial that spins if water is running.

If the water in the shower goes "up" when cold is being used, that just means that the pressure has dropped on the cold side, and the hot isn't being compensated for. Newer valves have pressure balancing.

An electric water heater will recover at about gallons per hour.

It might be that you have a hot water line leak...maybe under the slab. If there's one, there may be more than one.

First thing I'd do is make sure all faucets are turned off, then go look at the water meter to see if it is turning. If it is, you have a leak. Then, shut the supply valve on the WH, see if the meter now is stopped. That would confirm there's a leak in the hot water line somewhere. Your next task would be to identify where, and either fix it, or reroute the pipe with new, as if there's one leak, there'll likely be more if there aren't already.

Thats the thing. When I shut the supply from the WH off the water starts to run near the second bathroom. But I have seen no evidence of leaks anywhere as of yet. We haven't used that bathroom at all since we moved in. I'm not sure there are any lines under the slab. The lines run into the wall from the WH. I'll be more than likely going under the house to look around. I have noticed that the meter is moving but I'm not 100% sure right now. Too dark to look but I'll check it in the morning. Some of the people I've talked to so far have said that it might be a water pressure regulator or a reroute or something along those lines. Could that be an issue? I can understand that it may be a leak in the hot water line. That does make some sense. I may have to get someone out here to look at it.

If the water meter runs when you have all of your valves closed...there's a leak somewhere!

Another reason you may only get tepid water is if one or more of the single-handle valves in the house has failed and is creating an internal cross-over. This allows cold water to flow back into the hot line, making it warm. Different lengths of pipe or amount of fittings can create slight resistance differences in the flow path, and it can go either way, either warm in the cold line or cold in the hot line.

1. The "rushing" noise was probably crossover flow from the cold water line into the hot through one of your faucets, usually the tub/shower one
2. Heaters come the thermostats set for "slightly warm" so you have to reset BOTH of them to the desired temperature
3. A new heater would have absolutely no effect on how long it takes the hot water to get to the faucet.