Chrome Shower head attachment

Hi, I recently bought a Merck shower head, like this:

http://www.bathstore.com/files/PRODUCT_GROUP/787/LARGE.jpg

which came supplied with a compression elbow, one arm of which is 15mm, fair enough. But the larger olive measures about 18mm internal diameter, and seems very loose on the 15mm chromed pipe. I hand-tightened it, and it simply fell off.

My question is, would a couple of turns with a spanner be enough to secure a watertight fit, or do I need some sort of adapter, or do I need to wrap some PTFE tape round the olive?

TIA

Trev

If the olive is of the correct size then you would presume finger tight and a nip with a spanner would suffice. However some of the copper olives are very hard and crap. So i would suggest you apply some jointing compound and give it a good tighten. Or throw the olive away and get a brass one.