Todd,
A fair amount of experience with two-inlet FDCs with a single clapper and a 
bypass around the check valve.  I don't recommend it as the clapper can be 
unstable and slam shut...talk about water hammer!  I like Tom Worley's 
suggestion.
Dwight HavensFire Code Official - retired.
    On Thursday, March 28, 2024 at 10:55:32 AM EDT, Fpdcdesign 
<fpdcdes...@gmail.com> wrote:  
 
 To a certain extent, this is a rhetorical question. We can use the 1st floor 
hose valve on the standpipe as a flow outlet. I assume with the available 
water, flowing 250 gpm through a single 2-1/2” hose and Hose Monster is not 
going to be a problem. 
But the real problem is that there is not a good way that I know of to predict 
this. I won’t know until the job is done if there is enough water from the hose 
outlet to meet the requirement. Then if the system has to be retrofitted, it 
becomes a big deal and a big expense. How is everyone else handling this?
Todd G Williams, PEFire Protection Design/ConsultingStonington, CT860-535-2080 
(ofc)860-554-7054  (fax)860-608-4559 (cell)


On Mar 28, 2024 at 9:54 AM, <Jackie Ward> wrote:



Or mech-tee the riser and add a hose valve.
 
  
 
  
 
  
 
Thank you,
 
  
 
Jackie “JW” Ward
 
1-405-240-7076
 
  
 
From: Worley, Tom <t...@firefoe.com> 
Sent: Thursday, March 28, 2024 8:46 AM
To: Discussion list on issues relating to automatic fire sprinklers 
<sprinklerforum@lists.firesprinkler.org>
Subject: [Sprinklerforum] Re: BFP Forward flow test design
 
  
 
Just make the main drain 2½.  A 2” may even suffice depending on how the water 
supply is.
 
  
 
Thomas R. Worley
 
  Estimator/Design Manager
 
  Fire Foe Corp.
 
  999 Trumbull Ave.
 
  Girard, OH 44420
 
  P: 330-759-9834 x112
 
  F: 330-759-8949
 
  E:t...@firefoe.com
 

 
  
 
From: Fpdcdesign <fpdcdes...@gmail.com>
Sent: Thursday, March 28, 2024 9:38 AM
To: Sprinklerforum <sprinklerforum@lists.firesprinkler.org>
Subject: [Sprinklerforum] BFP Forward flow test design
 
  
 
I am working on a re-design of a system where I need to include a provision for 
doing a forward flow test for the backflow preventer (4”). Due to space issues, 
I would like to do a by-pass around the check valve to the FDC. Is there a 
problem with this due to the clappers in the FDC? 
 
  
 
Also, the building is Residential or Light Hazard and the maximum demand flow 
is around 250 gpm. If I have to add another outlet for the test, would a single 
2-1/2” FDC be acceptable? Unfortunately, I am not aware of any way to predict 
what would be required. Is there any rule of thumb for the design of these 
things? 
 
  
 
Todd G Williams, PE
 
Fire Protection Design/Consulting
 
Stonington, CT
 
860-535-2080 (ofc)
 
860-554-7054  (fax)
 
860-608-4559 (cell)
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