I have installed a hot water cylinder. I had to put 28mm x 1" female couplers on the heating coil threads. I put some ptfe on and wound right down to the back nut that is on the wall of the cylinder. but I am getting a very slow drip from each fitting. should I have put more ptfe tape on so as not to be able to reach the back nut. I cant tighten it anymore as they are too close to get a spanner on each nut. appreciate any advice. Thanks.