What should be applied to male pipe threads before assembly?

When preparing male pipe threads for assembly, it is essential to use a thick lubricant. This type of lubricant is designed to create a seal between the threads, preventing leaks and ensuring a proper fit. It can also facilitate tightening and loosening of the threaded components without damaging the threads themselves.

Thick lubricants and pipe joint compounds are specifically formulated for this purpose. They help fill in minor imperfections in the threads and provide a barrier against moisture and corrosion, enhancing the overall integrity of the joint once it is assembled.

Other options, while they might have some uses, do not serve the same purpose in this context. For instance, grease might not have the right consistency or sealing capability for pipe threads, and washing detergent or varnish are not suitable for lubricating or sealing threaded connections in a plumbing or piping context.