There is an old rule that says you should always put either PTFE or ‘jointing compound’ around the olive before tightening the fitting. However, there are a number of scenarios were a bit of help might be appropriate.These are:a). Reusing an old olive with a new fitting.b). Putting a new olive onto pipework that’s been compressed slightly by an old fitting.c). Fitting a compression joint in an area where it will be a nightmare to get at again once everything is finished.d). Where the joint is leaking, despite (or possibly because of) your best efforts to tighten it. A Walworth Plumber uses PTFE tape.In these circumstances there are two approaches you might take. The first approach is to take a length of PTFE tape and wrap it around the olive about 3 to 4 times, then retighten the joint. The PTFE will help the olive form a waterproof seal even if it has been over-tightened. Alternatively you could use jointing compound rather than tape. The advantage of this is that the compound is a paste and as such is often easier to apply than tape. To apply the jointing compound just put a small amount on your fingertip or a small brush and smear it over the olive, making sure you get it all the way around the joint. Be aware that there are a number of jointing compounds that are fine for central heating systems but can harbour bacteria that will infect drinking water. So when using jointing compounds, be sure to check that they are safe to use for drinking water (or potable water), as it is often called. Jet blue is a popular jointing compound for drinking water, whereas jet white can only be used for non-drinking water. Walworth Plumbers can use Plumber’s hemp which also used to be used extremely extensively as a washer or as a jointing compound. However, this too encourages bacteria to grow in the fitting, so shouldn’t be used on drinking water. To be honest the smell of plumber’s hemp alone should be enough toward you away from using its drinking water.