I am currently working on a project where we ran into a similar
problem (I think I mentioned it in earlier posts) The problem there
was that the water supply varies almost 30 psi at any given time of
the day. There were three water towers on the system that would fill
at random times (it has changed, but not sure how at this point). The
water company had no ideal until they put a pressure recorder on a
hydrant for about 5 days. This town does their own water tests and
they provide the data.
This type of thing is almost impossible to track. What are you going
to to, put a recorder on the pump for 3 days, find out when the
lowest pressure is and then schedule the test? Nice in theory, but it
is tough to get most contractors to do water tests anyway (from an
independent designer perspective) without adding that extra dimension.
The interesting thing with this job is that we are going to have to
add a fire pump and now we have to size it based on the maximum
pressure, not necessarily what we agreed on for the "typical"
pressure (the max was 92 psi and everybody agreed on 72 as the
pressure was above that 95% of the time)
At 09:31 AM 2/27/2009, you wrote:
Question for the lettered members and others with experience and/or
an opinion -
I recently looked at the riser of a new system installed in my home
town. The system requirement according to the hyd. calc. nameplate
states 377.9...@75psi. The system gauges read 60psi static.
When I contacted the water superintendent he stated the installing
contractor took the hydrant flow information used to design the
system. He also stated that he head been asked to have the
standpipe full and to have both Town pumps turned on before the
hydrant was flowed.
He continuede that it is standard procedure to have a water
department employee respond to the water plant for every fire
department discharge to turn on the pumps. He stated the standpipe
is filled once weekly prior to weekends so that water employees do
not have to work weekends then the standpipe is drawn down, filled
during the week.....
It appears the "best case scenario" was used in taking the hydrant
flow making the system suffient only when the standpipe is filled
and both pumps are in operation.
I do not see anything in 13 which tells anyone how to determine the
acceptability of hydrant flow data, however if the gauge states
there is 15 pounds less static pressure than what is required
residually for the system to operate - then there is a problem.
Is there any requirement for engineers or others to apply
acceptability standards to hydrant flow data or can the results
purposely be slanted? It seems the system will operate properly
Thursday 10am through Friday at 4pm.......
The local AHJ states he accepted the opinion and acceptance of the
engineer hired to review and accept the system. I do not know if
this firm or individual has any training in fire protection systems,
or if he has provided any such credentials to the AJH. This is in
the State of NY.
opinions? thoughts? code references? standard references?
thanks in advance,
Garth
retired fitter
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Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
www.fpdc.com
860.535.2080
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