5 Gal DM T@b Water Container Question

Hi everyone! I have finally played around with my water pump on my new to me 2005 DM T16 Tab. It works well except.....I am a bit concerned about the hissing noise and pressure build up within the container. Should I just use some plumbers tape on the cap and ignore or should I be concerned about the pressure? It’s coming from the large cap, not the smaller cap with the connection to the pump line. Thanks in advance! Oh and I searched the yahoo group with no luck as well.