Leak in the water tank

Hi
I have got a minor leak in the small water tank which is used along with the Pulsacoil 2000 boiler.
The water starts dripping from where one of the steel pipes is connected to the tank. So I am not able to fill the tank to a good height.
Any suggestions on what material should I use to cover the area around the joint which may prevent leaking?

Thanks in advance
Mukul

Empty the top tank.
Undo the connections
Remake the connection using ptfe tape.Wrap it in the direction of the nut when tightening it up.
And job done.

Just tighten it a little which may do the job. Make sure the tank is sitting flat and no pushing or pulling against the pipe.