I have a 40 gallon tall 1996 rheem gas hot water heater model 5v40-7 that is leaking from the drain valve can this be capped

SOURCE: dripping from drain spout

If you are refering to the "Dripping coming from the preasure tempature valve,Then just turn off the valve where the water goes into the heater and open the P/T valve with a bucket below it draining only emought water to get below the level where it reaches.     Normally the drain valves are plastic with a Male hosebib attached.  Attach a  garden hose to the rain and run it out to a point lower that the vaslve in order for gravity to drain the tank.The valve opens counter clock wise. If the valve is stuck or does not drain,and you have a foor drain handy,remove the whole valve and replace it with a boiler drain valve.  If The tank is located below the drain level then you will have to either pump or carry the drain water to the higher level.     Replace the P/T valve  and reinstall the associated associated piping. I would use tefelon tape on the P/T pipe theads.    You may have to open a hot water faucet in order for the air to replace the water in the tank ,in order to drain. 

SOURCE: Hot water tank leak

drain valve must have already been leaking, that's why someone put the cap on. It's ok to cap the drain but never the pressure/temp relief. If the water is coming out of the drain (not around it) you could either replace the cap or the drain valve to stop the leak - otherwise it's time for a new water heater.

SOURCE: GE 40 Gallon Natural Gas Tall Water Heater won't

Is it a new unit? If so, the safety mechanism may has tripped. If it is a GE built be Rheem, the safety device is a one time device - you have to replace the water heater. Check to maek sure you don't having a venting problem.

SOURCE: Rheem 40 gallon gas hot water heater, pilot light

To make a short story long (I need to include all details, sry)…

I got up one morning and realized that we did not have hot water. I re-lit the pilot light and as soon as the burner went out from heating the water up, the pilot light would go out. After reading several posts regarding this issue, it seemed apparent that the thermo-coupler was the problem. Since I am a little bit handy around the house and very tight when it comes to opening my wallet, I bought the device from Lowe’s ($8.98) that was recommended by my online advisors and after a few googles, figured out how to change it. No help. The pilot light still goes out.

I gave up and went to Home Depot to purchase and schedule the installation of a new hot water heater.

STICKER SHOCK

A new Direct Vent type water heater costs around $800 with an additional $450 for “special” installation. Add a few fees to that and the grand total came to about $1450.

I felt like I had no choice since my wife and 2 daughters refused to live their life without hot water and I had no clue about how to fix the dam thing.

The plumber assigned to the installation stopped by to evaluate the site conditions and quickly noted to me that the 8 year old water heater tank was in good condition and that the gas controller was probably faulty, which could be purchased online from the manufacturer. I quickly cancelled the Home Depot order and purchased the controller for about $120 after shipping and tax. Immediately after the installation it seemed that the problem had been solved. A few days later the pilot light went out.

I called the plumber and explained the situation and he recommended that I purchase another controller because the one that was shipped to me was probably bad. I searched around town and found a plumbing supply company that had the correct model in stock. Two days later the pilot light was out. I cleaned up the controller and returned it to the store and asked the plumber to please schedule a visit to repair this dam thing.

When the plumber arrived, he hooked up a gauge in several locations and confirmed that the correct amount of gas (cfm) was being delivered to the controller, pilot light and burner. He then proceeded to remove the fire box to make sure that the igniter, thermo-coupler and pilot tip were set properly. He inspected the pilot light tip and said that he found the problem. Using about a 1/64” tip drill (can be purchased at a welding supply store), he cleaned the tiny hole that releases gas to the pilot light. I felt a sigh of relief because I was certain that the problem had been solved. $65 dollars (plumber’s fee for an hour of work) and 4 days later the pilot light went out.

I called the plumber and he said that the controller that I purchased online must be bad. Too embarrassed to return to the first plumbing supply store, I found another one in a different town that had the correct model in stock. Three days after changing the controller the pilot light went out. I returned the controller and a six pack later I decided to do some extensive googling.

The key term here is “DIRECT VENT”. This seems to be a very common problem with direct vent water heaters and I was about to find out the reason for this phenomenon. I read a post by an individual who wrote that if the vent becomes detached that the inflow of air can become contaminated and extinguish the pilot light. I decided that before I spent any more money on a plumber that I was going to take the vent apart and find out what makes it tick.

My direct vent system has 2 parts to the venting, an inner pipe (3” nominal diameter) that serves as the exhaust and the outer pipe (5” nominal diameter) that serves as the internal flow of air which supplies the pilot light and burner with oxygen. On the outside of the house a vent hood helps to segregate the two by extending the exhaust about 3” beyond the intake. I looked into the hood at the end of the pipes and discovered that the internal pipe which consisted of a 2 piece slip joint had come loose from the elbow that sets on top of the water heater. This slip joint pipe was not attached at any point with screws or clamps and was loosely setting over the elbow on one end and into the hood on the other end, allowing it to detach. Apparently, when atmospheric conditions were right, the burner idled down from heating up the water and extinguished the pilot light because the intake was saturated with CO2 from the connection failure.

I purchased a section of 3” pipe that was long enough to be installed in one piece. I connected it to the elbow using a stainless steel hose clamp. I had to disassemble the pipe 3 times to make adjustments to the length and position before I got it right, but I should not have any more problems with the pilot light.

The problem here is time. It takes a lot of time to get this right. When the plumbing contractors installed this unit during the construction of the house, there was no one around to make sure that they got it right. It is probably common to use a 2 piece slip joint type connection, but I feel like it should be attached with screws or clamps. In my opinion it is not rigid enough and can detach easily, especially if it is not installed properly. A one piece connection that is attached at one end with a hose clamp and then held in place at the other end by the hood is fool proof.

SOURCE: I have a Rheem glas fury model 22-40 gas water - leaking

once they leak it's time for a new water heater. ther is no way to repair a tank leak