1) Turn the water heater temp back down.

2) Call a plumber NOW....don't wait for your guy to get back from vacation.

I suspect your heater's over-pressure valve has tripped -- which I hope it is because if it isn't you've got tank or line fracture. You've been leaking water as well as burning gas. Likely because of your turning up the temp. but don't know. Do suggest getting a knowledgeable person on-site pronto.

Your post actually proposes a number of questions so I will try to take them one at a time.

Your first question is whether or not you can place any blame on the plumber? That would primarily depend upon what type of pipe you have and how the alteration was made. If you have PEX tubing it would be very easy to cut the lines, then reconnect them because PEX is flexible enough that it can be slightly rerouted without imposing stress on other joints. On the other hand, if you have galvanized iron pipe, copper pipe or CPVC pipe teh material is rigid and it would require cutting the pipe, then installing additional pipe to make the crossovers. Simply bending the pipes from one side to the other then reconnecting could impose severe stress on both the repair joint and other joints on the run which could and often does result in the type of problem you have.

The problem here is that you had the job done by a Handyman/plumber and while in most cases the handyman/plumber has the necessary skills to perform a simple repair, generally they do not have any liability insurance and it is highly unlikely that they would have the ability to pay a claim even if you could get an ordered settlement. At best you could have that individual come back and correct the problem, but given that you already know the quality of his/her work, do you really want to trust another job to that person?

You stated that your water supply is unmetered, therefore the actual cost of the lost water is not an issue. On the other hand, we must consider the actual cost of additional property damage that might result from this leak, not to mention the cost of the gas being consumed in heating the lost water.

You could reduce the fuel consumption by turning the burner down to the pilot setting between uses, but that will do nothing to reducing the leak, therefore by the time you turn the burner up for your showers the entire tank will be full of cold water and it will require maximum firing to get the water up to operating temperature every time you want a shower.

There is a better solution. Keep in mind that all water pressure in your house, in both the hot and cold distribution system originates from the municipal main or well pump, but you have a shutoff valve on the cold water input line to the water heater. If you turn that valve off it will eliminate the pressure to the hot water distribution system which will in turn stop the leak, save for a very minor loss from the vertical standing head pressure of water in the system above the point of the leak.

By turning the cold water supply valve off, not only will it stop the pressure at the leak, it will also stop cold water from entering the tank and causing excessive firing of the water heater burner, thus it will simultaneously stop the system from wasting fuel energy.

The leak is under the house, which is raised, hence there is no damage because of the leak.

There does not seem to be a leak with the heater. However, the slab for the shed that contains the heater is low, and I believe that during big rains, it floods (and it has been just so raining, and the slab is coated with water); whether there was indeed another leak (or perhaps an intentional discharge?) at heater I don't know. I do know that there was a hissing sound by the bathtub, and no sound by the heater.

The piping was plastic at that point (it appears to be galvanized a few feet below). He rerouted the pipes by basically cutting the 2 pipes and put in some elbows and other sections.

asolo:

You seem to be saying that there was a resultant incident at the hot water heater - again, because of the raining, I can't tell if the shed was wet because of the rain or because of some fracture or intentional discharge at the hot water heater. But I can hear the leak below the bathtub - a slight sound when inside, but definitely noticeable outside right there. There must be a line leak there irregardless of what happened at the heater. Because there is not much crawl space and there was a huge puddle of water, I could not visually inspect it, and I have a hunch that I will need to wait for the area to dry off before anyone could get there as well.

lazypup:

As I had said, there is no damage to anything else. I was wanted to know if the plumber could be liable for somehow damaging the pipes right next to where he did his work. So it would not be a question of liability, but just simply fixing what ended up getting broken in the process of the original job. As for saving money, well yes, I don't want to be heating all the water just to have it leak. As I have said, there was no problem at all in getting sufficiently hot water to take a bath, so obviously the leak was smaller than the reheating capacity of the heater, but obviously the equivalent of 25 or so baths a day is expensive!

lazypup (again):

Now as for what to do, are you saying that I should leave the heater on, but simply turn off both the cold (input) and hot (output), but leave the heater ON? Would this be OK? If so, I can see your reasoning - the water in the tank would be static and heated properly, but just stay there. Then when I am ready to bathe, I just turn both those valves on (and starting the leak), run the bath water, then go back to heater and turn both values off again (and then of course bathe.) Is this what I should do?

both:

I know diagnosis is tough, but it seems that the factors in the failure are:

[1] the boosting of the temperature caused the pressure to go up

[2] the plumber, in moving around slightly the pipes, stressed the joints

Now, I am almost positive that I had boosted the temperature before the plumber did the work (although perhaps I did right after, I can't really remember.)

(I should say now that the pipes are old galvanized, perhaps as old as the house, from the 1920's!)

Because the flow loss seems to be rather small, it doesn't seem to be a catastrophic failure. So it would seem that the leak must be a joint. What would be the solution of a bad joint? Just simply take the joint off, put a bunch of teflon tape (or whatever) and put the joint back on? Or if it a crack, simply get an identical piece and replace it (or could this last scenario be much more involved?)

Also, if the joint happens to be right below where the plumber did his work, wouldn't that seem to be prima facie evidence that basically he had loosened up the joint to the point that it started leaking, and therefore his fault?

*** Please answer my question about how to deal with the situation until it can get fixed (i.e., is it OK for me to just turn off both lines to the heater while leaving the heater on, then when I need hot water, turn them the lines on to fill the tub (while leaking some), and then after my bath is full, simply turn both lines off again?) I can live with this solution while I wait for the water to recede and do some more investigation.

If you have a single handle valve in the shower I believe you can turn the valve 180 and that would have fixed the problem to begin with. You may not want to hear that now.

This is what lazypup said:

By turning the cold water supply valve off, not only will it stop the pressure at the leak, it will also stop cold water from entering the tank and causing excessive firing of the water heater burner, thus it will simultaneously stop the system from wasting fuel energy.

Notice he said the cold inlet not both shutoffs.