fixing bathtub faucet

[nereo]

I'd appreciate some feedback about whether I'm doing about this the right way. Normally I'd just look up the manufacturer's diagram, but I can't find a brand name or model number anywhere on this thing (it was installed when we bought the place).

Yesterday my bathroom faucet came apart when I tried to turn it.  The 'goose-neck' top detached and water started shooting everywhere.  Upon close inspection it seems this is exactly what it was designed to do, and the faucet head could be re-attached by tightening the allen-head tension screw in the back (in other words, it was just loose).

Easy enough - but now I have a secondary problem... the water now leaks around the base where the collar/trim ring sits on the tile.  It never leaked before.
So I took that off (another simple allen-screw) and saw three things
1) the o-ring at the very base (around the brass base near pencil in photo) looks a bit pushed into the seam.
2) instead of silicone caulk there's some weird plasticy membrane that's looks past its prime (see the pencil)
3) there is no o-ring around the outside of the collar/trim ring even though it looks like there's a channel for one.

here's what I'm thinking...
option 1) tear out that plastic membrane, lay down some bath caulk in its place and be done with it.  This might make it a bit harder to remove later, but I have no plans on changing the faucet.  One worry I have about this is what happens if moisture slowly drips past that seam into the enclosed space housing the tub.  It would only happen when the faucet was on, so maybe a few drips each time... but I'm not even sure how moisture would ever get out of there.... is there weep holes someplace or a drain?

option 2) pull out the o-ring that got pushed down into the seam.  I'lll probably have to replace it since I don't think I can pull it out without damaging it somewhat.  Add an o-ring around the outer-channel of the collar (is it supposed to have one?  It looks like it, but it was definitely not there before).  Tear out the plastic membrane .... maybe still caulk it?

Photos attached for clarification

[RichMoose]

I would replace the O-rings, use silicone to reseal, and re-install making sure everything is snug but not over-tightened. On most fixtures, the trim pieces are not designed to hold water so normally there's no O-ring there.

[Drifterrider]

I would visit a DIY big box store with the parts and ask for plumbing assistance.  Down here (US), I've found a lot of retired tradesmen now working at those stores.  They know stuff.

[Mother Fussbudget]

I would replace the O-rings, use silicone to reseal, and re-install making sure everything is snug but not over-tightened. On most fixtures, the trim pieces are not designed to hold water so normally there's no O-ring there.

Exactly this.  And taking the faucet neck with you to the 'home store' would also be a good idea. 

Those thin o-rings in the 3rd picture spaced 4-to-6-inches apart on the brass inner sleeve are probably the source of your leak if the collar around the tub faucet leaks while ON. 

If water is leaking while the faucets are set to OFF, then it's likely the thicker (but smaller diameter) rubber washer at the bottom of that filler neck assembly.  But it could also be the washers in the hot/cold handle assemblies.

[nereo]

I would replace the O-rings, use silicone to reseal, and re-install making sure everything is snug but not over-tightened. On most fixtures, the trim pieces are not designed to hold water so normally there's no O-ring there.

Exactly this.  And taking the faucet neck with you to the 'home store' would also be a good idea. 

Those thin o-rings in the 3rd picture spaced 4-to-6-inches apart on the brass inner sleeve are probably the source of your leak if the collar around the tub faucet leaks while ON. 

If water is leaking while the faucets are set to OFF, then it's likely the thicker (but smaller diameter) rubber washer at the bottom of that filler neck assembly.  But it could also be the washers in the hot/cold handle assemblies.

Thanks for the advice (to everyone).  The faucet leaks only when it is on, and it's a steady drip that comes out the base.  The two thin o-rings spaced ~3 inches apart are designed to 'seat' inside the brass pipe fitting.  The third thicker (but smaller diameter) o-ring seals the goose-neck filled and diverts water to the spray wand instead. 

One question left for all - what the heck is with that plastic membrane and is it best if I just cut it off and replace it with a new silicone caulk?  I can't figure out what it's there in the first place... it's like a semi rigid thick plastic - not anything I'd expect would be useful in sealing out water (even when new)

[Mother Fussbudget]

It's likely silicon caulk.  If it's a pre-fab rubberized ring, it might be hard to find a replacement, but silicon caulk should replace it just find. 

Carefully remove it, and also take THAT with you to the home store, and see what the plumbing guy thinks.  If all else fails, replace it with silicon caulk.