Recently purchased a rebuilt Procon rotary pump for my Elektra T1. Was having a hard time getting a watertight seal on the inlet and outlet threaded nipples that go into the pump. After putting 4 complete wraps of teflon tape (the thicker stuff too) and still getting slow drips, I decided that some type of thread sealant was maybe a better way to go as I worried that putting too many wraps of teflon tape around the male threads could actually cause damage to the pump body (of plumber friend of mine has warned me to never use more than 4 wraps max, otherwise you might actually crack female fittings....).

So in searching, I found this Gasoila stuff: https://www.amazon.com/gp/product/B008HPVAQ8/

It's non-toxic, NSF rated for water systems, non-hardening, and it has a working temp up to 600 degrees and will handle up to 10,000PSI on liquids. Best of all, a fairly large tube (more than enough to completely rebuild a couple espresso machines I'm sure) is only $4 Lastly, it worked great on my pump inlet and outlet nipples with zero leaking and no bad taste!