Quarterly Test of Main Drain

Q: Has the frequency for the main drain testing changed from annually to quarterly?

A: Yes… but not for all the main drain test locations. The new 2012 LSC now references the 2011 edition of NFPA 25, and section of NFPA 25-2011 requires once per quarter, one (not all) main drain test must be conducted on a system riser located downstream of the backflow preventer when the sole water supply is through a backflow preventer. This test must record the static water pressure, the residual water pressure, and the time required to restore water pressure to static pressure. This test is conducted with the fire pump off (if so equipped) and the jockey pump on.

You still must conduct an annual main drain test on all of the system risers.

Main Drain Tests

Q: Where are main drain tests required to be done? This is a large medical facility with nine story towers. Several fire mains feed the various campus buildings. Is the main drain test required to be done only where the fire mains supply the system risers, or does it also need to be done on each floor at the riser as well? Would you please supply your rationale for your answer?

A: According to the 2000 edition of the Life Safety Code, main drain tests are regulated by NFPA 25, Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems, 1998 edition. Section 1-5 of NFPA 25 defines a main drain as the primary drain connection on the system riser and also is utilized as a flow test connection. Section 9-2.6 requires a main drain test must be conducted annually at each water-based fire protection system riser to determine whether there has been a change in the condition of the water supply and control valves. NFPA 25 does not adequately define what a ‘system riser’ is, so we turn to the Handbook for NFPA 13 Standard for the Installation of Sprinkler Systems which identifies a ‘system riser’ as the above ground horizontal or vertical pipe between the water supply and the mains (cross or feed) that contains a control valve (either directly or within its supply pipe) and a waterflow alarm device. A system riser is more than just a subset of the term riser, which is broadly defined as any vertical piping within the sprinkler system. As indicated by the definition, a system riser can be any aboveground pipe in a vertical or horizontal orientation installed between the water supply and the system mains that contain specific devices. By this definition it appears one could loosely define the locations of a main drain test to be conducted wherever there is a control valve and waterflow alarm switch. In a large multi-story facility such as yours, that would most likely require a main drain test at least on every floor, possibly more. The Accreditation Organizations (AOs, such as Joint Commission, HFAP and DNV) typically do not seek this level of compliance. Most of the AOs only expect main drain tests to be conducted at the base of the risers of the sprinkler system, not at every floor. However, depending on your state agency surveyors who conduct CMS validation surveys, it is very reasonable and possible that they will expect the main drain tests to be conducted at every floor. To continue with additional information, the purpose of a main drain test is covered in the Annex section A-9-2.6, which says main drain tests are used to determine whether there is a major reduction in waterflow to the system, such as might be caused by a major obstruction, a dropped gate, a valve that is almost fully closed, or a check valve clapper stuck to the valve seat. A large drop in the full flow pressure of the main drain (as compared to a previous test) normally is indicative of a dangerously reduced water supply caused by a valve in an almost fully closed position or other type of severe obstruction. After closing the drain, a slow return to normal static pressure is confirmation of the suspicion of a major obstruction in the waterway and should be considered sufficient reason to determine the cause of the variation. A satisfactory drain test (i.e., one that reflects the results of previous tests) does not necessarily indicate an unobstructed passage, nor does it prove that all valves in the upstream flow of water are fully opened. The performance of drain tests is not a substitute for a valve check on 100 percent of the fire protection valving. The main drain test is conducted in the following manner:

  1. Record the pressure indicated by the supply water gauge [Static Pressure]
  2. Close the alarm control valve on alarm valves
  3. Fully open the main drain valve
  4. After the flow has stabilized, record the residual (flowing) pressure indicated by the water supply gauge
  5. Close the main drain valve slowly
  6. Record the time taken for the supply water pressure to return to the original static (nonflowing) pressure
  7. Open the alarm control valve

Sprinkler Riser Main Drain Tests

sprinkler_class2pg8pic1[1]NFPA 25 (1998 edition) section 9-2.6 says main drain tests are to be conducted annually at each sprinkler system riser to determine if there has been a change in the water supply, piping or control valves. The original purpose for main drains on sprinkler risers is to drain water from the overhead piping after the system is shut off.

 But the added value of the main drains is to perform the test to determine whether there is a major reduction in water-flow to the system, such as might be caused by the an obstruction from a dropped gate on a valve, a partially closed valve, a check valve stuck on its seat, or a foreign object like a rock or a tool left in the pipe from a recent service.

 The Annex section of 9-2.6 does allow standpipe risers to have their main drain tests performed at the low point drain where the water enters the building, but that option is not permitted for the sprinkler system risers.

 A large drop in the full pressure of the main drain test when compared to previous tests normally indicates a dangerously reduced water supply. After closing the main drain test valve, a slow return to normal static pressure is confirmation of the suspicion of a major obstruction, and is just cause to investigate why the water supply is reduced. A main drain test is considered satisfactory when the pressures and time to restore to static pressure are nearly the same as previous main drain tests.

Please remember that sprinkler riser main drain tests are performed at the sprinkler riser – not at the location where the main water supply enters the building. It is not unusual that the older hospitals are not outfitted with the main drain test valve and pressure gauge on each riser, but that is what NFPA 25 requires. Since each sprinkler riser is supposed to have a main drain test conducted, that means you need to have the same number of main drain test results. Whatever number of risers you have, that’s how many main drain tests you should have documented each year.

 Main drain tests are required annually at each system riser, and downstream of any valve that is shut-off, then re-opened. The main drain tests should be coordinated to be performed just after the annual sprinkler control valve exercise. Here is the procedure to conduct a main drain test:

With the fire pump off, but the jockey pump on:

1.     Record the static pressure.

2.     Open the main drain valve slowly.

3.     After the pressure gauge has stabilized, record the residual pressure.

4.     Slowly close the main drain valve.

5.     Record the time it takes to return the residual pressure back to static pressure.

 This main drain test should provide the following findings on the test sheet:

  • Static pressure
  • Residual pressure
  • Time to restore back to static pressure

These findings should be compared to previous main drain test findings to determine if they were consistent. If they are not consistent with previous main drain tests, then an investigation should be conducted to determine if there is an obstruction in the sprinkler water supply.