Obstruction Investigations
NFPA 25, 2002 edition, section 13.2.1. is meant to be a minor internal pipe inspection done every 5 years, whereas section 13.2.2. is a thorough investigation only done when needed. Every 5 years an inspection is done according to section 13.2.1 by removing just 1 fire sprinkler head and 1 flushing connection and looking to see if there is any evidence of obstruction. If there is no evidence of obstruction, then an investigation is not required, and this minimal inspection does not have to be done for another 5 years.
Yes, it is true that NFPA 25 does not limit the obstruction investigation to dry systems, as seen in Table 5-1. In annex D3.2, however, it says that when there is both a dry and wet system, check the dry system first. If the dry system is ok, then don’t bother to check the wet system, but if it isn’t, then check the wet system too.
If there is evidence of obstruction, then a full obstruction investigation is to be done according to the rest of section 13.2. This is a big deal and tends to be very expensive, especially where flushing is involved. During any inspection, if any of the 14 conditions of section 13.2.2 are discovered, then the obstruction investigation is warranted at that time, with the quick-check inspection of section 13.2.1 done every 5 years from the time of correction onward. The obtruction investigation, depending upon what is discovered, may require flushing for a small part of the system, or for the entire system. Repairs and/or replacement may be required for a small part or a large part of the system depending upon what the obstruction investigation reveals.
In summary, here is the intent of the code, "See if its broken. If its broken, then figure out how badly it's broken and then fix it. If it's not broken, then don't fix it."
The 2008 edition of NFPA 25 clarifies this whole section. The 2008 edition is now out, and will be adopted later this year by our office. This 2008 edition makes clear the difference between "inspections" and "investigations" in their section 14.2.
[Posted 3-14-08, then updated 3-19-08 to include the second paragraph for clarification]
