How do I find a sometimes small leak?

[Indiana Bob]

Here is my problem, my hot tub leaks, but only some of the time. I keep it hot and going and it won't leak for a week then it may leak for several days then stop. Here is my question. I drained the tub today and the corner from which the leak is occuring has three small non movable jets (first picture below) it seemed to me they were all loose, but one even more than the others. When these are installed do they not require sealant around where they screw in? Or the outer flange? There is no gasket or "O"ring seal on the back side. This tub is a rotational molded tub so access is extremely limited from underneath. When the tub decides it is going to leak if I remove the access door I can see it drip but since the insulating foam is still in place I cannot reach it I can only see it drip. Suggestions anyone? Thanks in advance for any help you can offer.     

[RDspaguy]

Those should have an o-ring in the jet body that oes against the back of the tub. They are also usually caulked  there as well. They do have a gasket that can go on the flange, but it can still leak at the threads. I would caulk the flange and first half of the threads and screw it down snug.

[Indiana Bob]

 When you caulk should I use clear silicone? Or is there a better product? Thank you for your response! 

[RDspaguy]

Yep. Clear silicone.

[Indiana Bob]

Thanks again!