TECHNICAL 49
How to select and apply a pipe thread sealant
By Erin Bullock ( September 16 , 2021 . www . plumbermag . com )
Here are some tips on how to use sealant tapes and pipe-joint compounds .
How you can consistently achieve a watertight and airtight seal on pipe connections :
When to use a thread sealant Almost all plumbing systems ( natural gas pipe , a compressed air pipe , or a showerhead and beyond ) will have a section where a threaded connection is required . Threaded pipe and fittings are considered either male and female and most commonly contain NPT ( National Pipe Tapered ) threads .
NPT means that the male and female threads are tapered when cut , allowing for easy alignment of the male threads at the start of the joint assembly . As the joints are tightened , the harder it becomes to turn .
These joint assemblies cannot achieve a watertight / airtight seal on their own . As a result , when assembling , an approved thread sealant is required to fill the remaining voids in the root of the threads to create a seal .
How to choose a thread sealant What type of sealant should you choose ? Thread sealants are available in either a tape or a pipe-joint compound ( often referred to as ‘ pipe dope ’). Each has distinctive features and benefits but knowing which one to choose and how to apply it to your pipe ' s surface will save you time and frustration .
Colours are used as visual identifiers to show a person what is flowing through a piping system . For instance , yellow thread sealant tape is required by most municipalities when assembling a gas piping system . Generalpurpose tapes are usually white and are also available in grey , which makes it more aesthetically pleasing when used on pipe materials that are similar in colour .
Widths include 1 / 2-inch , 3 / 4-inch , and 1-inch . A 1 / 2-inch tape is ideal for smaller-diameter pipe . When assembling larger-diameter pipes , 3 / 4-inch or 1-inch would be best because provides better coverage on the threaded section of the pipe .
Thickness is usually referred to by ‘ mil ’. Higher mil thickness reduces the number of full wraps necessary to create a water / airtight seal . Density refers to the pipe ' s ability to be compacted into the root of the threads . Tapes higher in density prevent excess stretching during assembly , which would lead to less compaction and possible leak paths .
Pipe-joint compounds , such as Hercules Megaloc and Hercules Pro Dope , should be selected based on pipe and fitting material compatibility , chemical compatibility and temperature performance ranges . To determine pipe-joint compound compatibility and temperature performance ranges , refer to manufacturer submittal sheets .
Material compatibility is important to know when assembling a threaded joint . For instance , if a joint compound is used on an incompatible material , it can cause the material to degrade rapidly and lead to a possible failure .
Chemical compatibility is another factor to consider when determining what pipe-joint compound to use . The chemical composition of
November 2021 Volume 27 I Number 9 www . plumbingafrica . co . za