Gas water heater leakage?

Carefully and away from the hot water that will discharge, trigger the pressure relief valve few times open and close. This most likely will clear the rubber seal inside and will seal for good. It's works for me most of the time. If this does not do for you then you must replace the pressure relief valve with a fresh one. CAUTION: If you replace that valve, you must turn the temperature down to the minimum and allow the water heater tank to cold down enough to avoid scalding water burns. replace the valve and make sure you use teflon tape or pipe compound on the threads to avoid leaks. I hope that you have the average skills to complete this task, otherwise you will need to call the money hungry plumber in town and pay the big $$$. Good luck...!

When you refer to the "pipe at the top", I assume you're referring to either the cold water inlet or hot water outlet that's leaking.

First, the pressure relief valve will not solve anything. The pressure valve would trip long before the pressure built up enough to cause a good joint to leak.

Your problem sounds like either a loose or corroded connection. Try tightening the joint. Don't wrench on it for all you're worth. It should be tight, but not wrenched hard. That's a good way to strip threads.

If tightening the connection doesn't solve the problem, you've got a corroded fitting either at the hose or the tank. You'll have to shut off the gas and the water supply to the heater, and take apart the leaking connection. You'd be wise to check the other one, too. It's possible that the other connection could also be bad, but not yet to the point of leaking.

If the threaded nipple on the heater is rusted, remove the rust with a wire wheel on a drill or a wire brush. Use pipe thread sealant when you reconnect the fitting. Sealant will fill larger voids than Teflon tape will.

Sometimes you can just tighten down the connection to stop the leak, but if its just rusted out and in bad shape just replace it, its real easy. Turn main water off, open up lowest faucets thruout the house to drain water in pipes, take off connection, replace. If you have a mess of piping there and its a hassle you could always just cut the copper pipe and use a sharkbite connector, takes like 2 minutes to replace.

If water is dripping from the water heater, determine where the drip is coming from. A couple of the most obvious sources of a drip are the pressure-relief valve and the drain valve. Less obvious leaks may be coming from condensation or from leaky fittings (see above for dealing with leaky fittings).

Leaking temperature-pressure relief valve. It’s quite common for water to be dripping from the temperature-pressure (TP) relief valve, which is designed to release water when it senses excess pressure. Excess pressure can be caused by the temperature being set too high, by the main water supply pressure to your house being too strong, or by special valves that reduce water pressure in your water supply system not allowing for hot water expansion in the tank.

In some cases, the TP relief valve itself may be faulty—if it is, it will need to be replaced right away. Consult your owner’s manual for instructions on what to do and see How to Replace a Water Heater Pressure-Relief Valve, or contact a plumber who works with water heaters. A working TP valve is absolutely necessary to prevent excessive build-up of steam that could cause a water heater tank to explode.