I've got a horse rug dryer, basically a closed circuit of pipes filled with water/anti freeze, with an immersion coil at the bottom. I had to put it on it's side and unscrew the immersion part and top up the water, now when I stand it upright it leaks. I've replaced the washer to no avail. I've got some plumbers mate, do I put it around the edge once I've tightened the thread, or put it between the 2 surfaces including on the washer then tighten the thread so that it oozes out?