[amandar2]

The water heater blows the T.m.P. valve every time the water is used.I am on a well system there is also a lot of sediment in the well.the water pressure fluctuates dramatically as if the well pump keeps getting triggered,could this be a problem with the bladder tank? If it is the bladder tank could you tell me a way to check it? I have already tested the air valve on top of the bladder tank and only pressurized air came out.this has become a serious problem.

[hkstroud]

It is unlikely to be a well problem.

That valve is a Temperature and Pressure release valve (T&P) not TmP.
It opens to release water if the temperature exceeds specified temperature or if the water pressure exceeds a specified pressure. They come preset. Mine is set to release at 150 pressure or 210 degrees. If your water temperature is that hot you should know it. If the pressure is that high you should also know it.

Unless you water is excessively hot or unless you really get a burst of water when you first open a hot water valve you have a defective T&P valve. Not expensive and fairly easy to replace.
Turn off cold water input valve to water heater. Open a hot water valve somewhere, then open the water heater drain valve and let it drain for a few seconds.
Cut the discharge piping coming out of the T&P. Unscrew the T&P valve and replace it. Wrap the threads of the new T&P valve with 4 wraps of Teflon tape or apply pipe joint compound to threads . Screw in new T&P valve. Reconnect discharge piping. Assuming you have copper piping, you can reconnect piping with s soldered coupling. If you do not know how to solder pipe you can reconnect pipe with a Sharkbite push-on coupling.

You should not normally open a T&P valve manually. Sediment can be brought to the valve causing it to not re-seat properly. When that happens they will leak continuously.