My heater control valve has a small leak it looks like water is dripping from it

TP valve is dripping? Or drain valve is dripping?
Or water heater is rusted out?
http://waterheatertimer.org/Leaking-water-heater.html

Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

it sound like you are over heating the unit

What is the warranty on this tank?
Warranties covered failed tank.

Does the tank wall have a leak?
If the tank is leaking on top around inlet pipes, or leak is coming out of weld around TP valve, then water heater must be replaced.
Copy following link for troubleshooting and method for prolonging life of water heater by turning off heater except to make batches of hot water.
http://waterheatertimer.org/Leaking-water-heater.html

You can buy water heater at local box store. $350 for gas and $230 for electric, then get store coupon or offer 10% less than sticker price.
Electric water heater is simple to replace.
Gas water heater takes more steps, but how-to step-by-step appears on following link:
http://waterheatertimer.org/How-to-install-gas-water-heater.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

If the drip is coming out of drain valve: Put a hose cap over end of drain valve.
If water is seeping out of cracked drain vale, then replace it.
If the leak is seeping around previously sealed threads, then tank may be rusted beyond repair.
http://waterheatertimer.org/How-to-replace-water-heater-drain-valve.html
http://waterheatertimer.org/Leaking-water-heater.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

besides the cartridge, the small brass screw/valve and its seat can cause this leak

Make sure any water valves (Cold or Hot) for water heater are not leaking first. Gate valves may leak at the packing nut over time and drip on top of tank. If water is leaking from the top of the water heater itself the tank is corroded and water heater will need to be replaced.
RJ

Water heater should be set in a drip pan.
Otherwise, put 1 gallon bucket under TP release pipe to catch water.
http://waterheatertimer.org/Water-at-bottom-of-water-heater.html#drip-pan

When you say relief valve, I assum you are talking about brass valve located on top of tank or near top of tank. This is TP valve and a pipe connects to this valve and runs down to within 6" of bottom of tank. TP valve has a small lever on it.
If you are talking about tank drain valve located at bottom of tank, then add a comment.
Following information is for TP valve.

Dripping TP valve can be caused by 3 different thing:

1) Obstruction inside TP valve. Open TP valve for a moment to flush away particles and slowly lower lever back down. See if water stops dripping, if not, then replace TP valve

2) Defective TP valve: replace TP valve. Turn off electricity to water heater. Let heater cool for several hours so you do not get scalded. Close shut off valve located above tank on cold side. Open tub spout to relieve pressure, open tank drain or open TP valve and empty water below TP valve level. If TP is located on top of tank, not much water has to be drained. Tank is under press when hot, so be careful. Put teflon tape on new valve and install with big pipe wrench by turning clockwise until TP valve is very tight.

3) Overheating tank. TP valve is temperature-pressure valve. If tank water is over 150 degrees, the TP valve starts drizzling hot water to relieve tank pressure.
Lower tank pressure two different ways:
a) turn down thermostat
http://waterheatertimer.org/How-to-adjust-water-heater-temperature.html
b) install expansion tank on incoming cold water line
http://waterheatertimer.org/Water-at-bottom-of-water-heater.html#expansion-tank

You'll obviously have to determine where leak is coming from, then we can decide how to stop it. If it's the pressure relief valve outside, and it's only a small drip, that is normal, but you can try lifting arm on relief valve and cleaning it out a little to see if that helps clean it out. BE CAREFUL when water is hot, that you don't burn yourself, thus better to try it when cooled down. If it's dripping, or running out too much, it may be that water is too hot, or water pressure is too high as well, so check that as well. Usually smart to install a pressure regulator in line from hose to trailer. If your running off on board pump, not very likely that pressure is too high as they are usually set at 40-50 psi, which shouldn't cause that. If water doesn't feel hotter than before, then best to replace pressure relief valve, if that's where dripping (excessive) is coming from.

If you are reffering to the drain valve at the bottom of the hot water tank. It may be leaking due to the O ring being cracked or worn out. You can either drain the tank and replace the valve or you can buy a hosebib brass cap and thread it on the existing valve. There is no cause for alarm when doing this as this valve is just to drain the tank when replacing your hot water heater

look can look to wear the water nis comeing from