What in the HDPE is going on? - REVISITED

After the original post, What in the HDPE is going on?, I received several comments and some other useful information.

A practice that I have started is to make any contractor that submits plans utilizing HDPE for fire service undergrounds, to also submit cut sheets for the exact brand/type of HDPE beign utilized.  A recent submittal by Sim-Oak Mechanical produced a wealth of information. 

• HDPE approved for fire mains is black with a red stripe.
• HDPE approved for fire mains needs to be DR-9, as DR-9 is rated for the NFPA 24 required 200psi pressure test.
• HDPE approved for fire mains should comply with AWWA C906 or ASTM D3035 or NSF/ANSI 61

Here are some reader comments, via Linked In:

Dominick Kasmauskas • If it meets the NFPA Standards for Fire Protection and is allowed by your local or state codes and standards, plus the underground contractors are trained and/or certified (if there exists a certification) for using the process, the item in question will generally be supported by the fire sprinkler industry.


ALBERT MIGNONE • HDPE [high density poly ethylene] can do many things but cross-linked LDPE [low density poly ethylene] might be better. It does almost everything the HDPE can do but with a better coeficient of friction. [You can bet more water through the same diameter tubing.]

Pex and/or Fire Pex are good alternatives and are making headways into sprinkler systems in the central and western parts of the country. The Pex materials carry warranties that other pipes and tubing do not have. They also are less likely to fail in some freeze situations because of how they are installed.I would like to see some data on success or failures and real cost numbers for installations.

What in the HDPE is going on?

National Fire Protection Association, Standard for Installation of Private Fire Service Mains and Their Appurtenances (NFPA 24), lists the requirements for underground piping serving fire sprinkler systems.  Typically, PVC DR-14, or ductile iron, pipe is used for fire service undergrounds.  However, it is becoming more common to see the use of HDPE pipe being utilized for fire service mains.

HDPE, high-density polyethylene, is polyethylene thermoplastic made from petroleum.  Per NFPA 24, Table 10.1.1 HDPE is permitted for use as a fire service main provided it meets AWWA C906 standard, and is specifically UL listed for use as fire service main/underground piping (this documentation should be submitted with the plans for review).



HDPE shall be tested the same as  all underground fire service mains per NFPA 24:10.10.2.2.1 -

All piping and attached appurtenances subjected to system working pressure shall be hydrostatically tested at 200 psi (13.8 bar) or 50 psi (3.5 bar) in excess of the system working pressure, whichever is greater, and shall maintain that pressure at ±5 psi (0.35 bar) for 2 hours.
 
An important observation when hydrostatically testing HDPE is that a standard 200 psi hydrostatic test will fail. If there are no leaks, the pipe stretches and will show a drop in pressure. Generally, the best way to test this pipe is to pressurize it and leave it pressurized and then come back later and bump the pressure back up to 200 psi after it has dropped to a point where the pressure holds steady. Then do the hydro. If there is a leak, the pipe pressure will continue to fall and never stabilize.

This is just a brief introduction to HDPE piping used for fire service mains.  What are some other challenges that you have found with this pipe? Where have you seen HDPE utilized successfully? How have you seen HDPE fail?