Technically, it IS a modification, and generally modifications need to
comply with current codes. Unless of course, waived by the authorities
having jurisdiction. Best check it out.

Tony 

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Ed Kramer
Sent: June 4, 2008 10:32 PM
To: [email protected]
Subject: RE: calcs with pipe replacement

If I had high confidence of all the following, I wouldn't see the need for
new calcs:
        -  Strictly pipe replacement (no added offsets, elbows, riser
nipples, etc)
        -  The original calcs were accurate (done properly and reflect 'as
built' conditions)
        -  Water supply hasn't deteriorated.

A bit of a side note - if the attic has a roof with slope greater than 2/12,
the design area very likely didn't include a 30% increase for the slope.
That requirement didn't appear in 13 until 1996.  But since the pipe
replacement is legitimately a repair, you probably don't need to meet any
standard other than what was in effect 17 years ago. 

Ed Kramer
Littleton, CO


> I walked through an attic this afternoon where all of the existing 
> mains need to be replaced. The piping is 3" schedule 10 black steel, 
> that is developing leaks after 17 years (we found another one on our 
> tour). The proposal is out there to replace the existing with 3"
> schedule 40 galvanized (and provide proper pitch). I did a couple of 
> quick calculations and at 250 gpm, the friction loss per foot for the 
> two pipes is very close to the same. (.077 for the sch 10 black v.
> .075 for the sch 40 galv). My guess is that the difference in pressure 
> would be about 0.75 psi. The calc has about 12 psi remaining. If this 
> was strictly a pipe replacement (no other modifications), would you 
> recommend new hydraulic calculations?
> 
> Todd G. Williams, PE
> Fire Protection Design/Consulting
> Stonington, Connecticut
> www.fpdc.com
> 860.535.2080

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