There are many different products available for use in the plumbing trade.  These products can range from harmful, to questionable to necessary.  There is also a lot of confusion about which product to use, when to use it, and where to use it. 

Below is a list of the most common products, with a short explanation of each one.  

1. Thread paste.  Also called “pipe dope”, thread paste is probably the most used product on a plumber’s truck.  The main function of pipe dope is to seal threaded connections by filling in the tiny voids.  Applying the paste will also act as a lubricant and help to tighten the connection a little better.  There are many different kinds of thread paste on the market, and some contain different chemicals.  You should always be sure that the paste you are using is ok for the material you are using it on.  Some pastes should not be used on plastic threads.  There are a few other situations that plumbers like to apply the paste, such as on the mating surfaces of certain kinds of unions, inside compression fittings, inside flared connections, or on the bottom of certain types of gaskets.  

2. PTFE Tape.  PTFE (polytetraflouroethylene) tape, or thread tape, is commonly (and mistakenly) called Teflon tape.  Since Teflon is a trademarked brand of the DuPont corporation, this product should not be called “Teflon tape.”  On threaded connections, PTFE tape can be used in place of, or along with pipe dope.  I don’t really have a preference either way.  If it is a connection that I most definitely do not want to have to fix, I will usually use both.  There are also certain devices that will call for tape specifically because it can be harmful if paste is introduced into them when the water is turned on.  It is important to not “overwrap” the threads with the tape, as this could possibly result in putting too much stress on the female fitting and crack it.  

3. Plumber’s putty.  This is probably the most widely misused plumbing item there is.  There are many times that I come across putty being used in place of paste or tape, and that is always a sure fire leak.  Putty should only be used on the underside of something that will be tightened or compressed down, such as the underside of sink drains, shower drains, and bathtub drains.  Some plumbers will use it underneath stainless steel sinks to seal them to the countertop as well. In the old days, it was used to seal toilets to the toilet flange at times.  

4. Latex caulk and silicone caulk.  Caulks and silicones should never be used to seal any piping.  They should only be used to seal fixtures down, or seal around areas that should not allow water in.  Examples includes, caulking down sinks, tub spouts, outside penetrations, maybe even faucets.  Some plumbers like to use silicone on the underside of sink, shower and bathtub drains in lieu of plumber’s putty.  I do not recommend this for two reasons: 1. It is very messy, and 2. If you ever have to remove it, good luck. 

5. Plumbers grease.  Any time you take a faucet apart, grease up everything!  This includes O-rings, threads and any moving parts. 

6. Flux.  Flux is what you put on copper or brass pipe to prepare it to be soldered.  It cleans the pipe and allows the solder to “flow” into the fitting. 

7. Draino.  Don’t use it, ever.