The members have given excellent help here, but as Slim indicated using sealant, tape, etc is not effective.
The metal in some hoses is very hard, and needs a great deal of tightening force to get it to "Sink in" the softer aluminum tube seats.
The biggest leaker is the "inside" ram hose on the control valve. Folks tend to put both hoses on the control valve, then try to tighten them. Can't be done. Put the inside hose on first tighten with a open end wrench---Go get your Vice Grips, carefully clamp down on the flats of the nut, turn the dam thing till it screams!
Now install the outer hose, tighten same method.
All the other hoses can be tightened Hell For tight with the vice grips. YES, you can use Vice Grips and not destroy the nut if done properly. Much more leverage this way.
Hope this helps.
Dan @ Chockostang