What should accompany sprinklers that have nominal k-factors smaller than 3/4 of an inch?

Sprinklers with nominal k-factors smaller than 3/4 inch require a listed strainer to ensure proper operation and maintenance. The primary function of the strainer is to filter out debris and particulates that could clog the sprinkler heads. When these smaller k-factor sprinklers are in use, the flow of water is relatively lower, making them more susceptible to blockages. Without a strainer, dirt and other contaminants can enter the system, potentially leading to malfunctions, inadequate coverage, or even total system failure.

The inclusion of a listed strainer helps in protecting the integrity of the sprinkler system and ensures that the sprinklers can operate effectively and efficiently when needed. This is particularly critical in fire protection systems where reliability and quick activation are essential for safety. In many codes and standards, the requirement for a strainer with smaller k-factor sprinklers acknowledges the increased risk of operational issues stemming from sediment or debris in the water supply.