Drip legs versus sediment traps, what’s the difference? Many often refer to these interchangeably and while their design can be exactly the same, it is their purpose that varies. In short, a drip leg catches liquids, while a sediment trap catches debris. The easiest way to remember this is to associate drip with wet and sediment with debris.
Drip Leg
NFPA 54 3.3.31 calls a drip leg just a drip and it is defined as “the container placed at a low point in a system of piping to collect condensate and from which it may be removed.” Further in the code book, 7.6.2, it is outlined that they shall be installed only in such locations that they are readily accessible to permit cleaning or emptying. They should not be located where the condensate is likely to freeze. There are no design parameters/requirements listed in the code book.
Sediment Trap
There is no definition of a sediment trap listed in section 3 of NFPA 54. They are, however, covered in section 9.6.8. It states, “Where a sediment trap is not incorporated as a part of the appliance, a sediment trap shall be installed downstream of the appliance shutoff valve as close to the inlet of the appliance as practical at the time of appliance installation. The sediment trap shall be either a tee fitting with a capped nipple in the bottom outlet, as illustrated in Figure 9.6.8, or another device recognized as an effective sediment trap. Illuminating appliances, gas ranges, clothes dryers, decorative appliances, and outdoor cooking appliances shall not be required to be so equipped.” I bolded that last sentence for emphasis as this is a common argument I have heard. People don’t fully understand where sediment traps are required. Another point of confusion is how to build a sediment trap. Figure 9.6.8 is to the right and it has specific details that must be followed!
I hope this month’s information has helped better understand the difference between a drip leg and a sediment trap, as the terms cannot be used interchangeably. I also hope it better defines what a sediment trap is and where it should be used. Please reach out if you have any questions and stay safe out there!
Product Spotlight
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Email Darren: Dmcardle@gardnermarsh.com
