I usually lubricate it once a year, or whenever I notice that it requires it during my regular filter maintenance.Do I need to lubricate it by myself later? What I can you to do that?
Double tap valves are safe to use, provided the O-rings still form a tight seal. Leaks can occur if the O-rings are old/cracked or if you did not tighten them properly.One more question, is Double Tap Valve rise the risk of leaking or it's safe?
Yes, this is fine.It's OK if the water (a little) stay on O-ring after the maintenance?
+1For lube, I use Vasoline on most all O-ring seals. I wipe it on and then pretty much wip it all off but leave is feeling "greasy"? It is good to also add some to the small O-rings on the double taps as well as the big seal. Just a once in a while thing to keep them from drying out.
A point on the double taps to keep in mind. They do not have to be tightened so that they are hard to turn loose again. The screw part only serves to keep them from backing apart. The actual seal is from the O-ring being compressed as it slides into place. No purpose in killing it when screwing it together.