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bucket test for 13 system?

C

cheyer

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Nov 3, 2009
Messages
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Location
Sunny California..well mostly..
Happy New Years All!

Question:

A new 4 story office building, fully sprinkled, nearing the end of construction...the approved plans have a hydrant test report done about two years prior...if there was any concern about the available water supply for the system, in lieu of another hydrant flow test, would you ever conduct a bucket test on a 13 system?

And if so would it then require flowing out of all the heads (12 in this case) in the most remote area? Would this be a practical solution?

Anyone run into a similar aituation?

Thanks
 
I can't imagine a scenario where it would be more difficult to run a new flow test than to run a bucket test on 12 heads. How big are your buckets?

Is there some obstacle to running a new flow test? Or are you just exploring the options?

Is there reason to suspect that the original flow test is no longer valid? In my experience, it is common for the fire department to accept flow test results dated within 12 months of plan check sumbittal. Depending on how fast contruction moves, it's not uncommon to finish 2-3 years after the date of the original flow test.
 
RBK:

Our water dept. has been behind for sometime with their flow testing, and I can only imagine what the cost would be to have them perform an actual test (very busy intersection)..the city collects a fee and will provide a "copy" of the latest one done, which in this case was about two years prior to the start of installation.

I am exploring options, and actually the contractor would much rather go with the bucket testing vs. a new flow test...but the question I am asking myself is any of this even necessary?
 
Just do a flow test. Pick non traffic time

Also what I'd the main reading at the riser and what does it go to when a main drain test is done???

What is the required pressure at the riser???

What do the hydraulic calculations show as safety factor????
 
Do you have the hydraulic calculations? If so how big is the "safety cushion" i.e. what they need psi and gpm vs what they have gpm and psi. IF the cushion is say less then 5 psi or less, then run another water flow test. If you have a cushion of 10 psi or more do not worry about it.

OR what is the demand for the system in psi and gpm at the base of the riser, the info should be on the data placard on the riser? Conduct a main drain test with calibrated gauges and see what your drop is. How close is the psi on the placard to the psi on the gauges?? Since this is an office building, the sprinkler demand must be about 150 gpm. Depending on the size of the main drain pipe, 2" say, you should have no problem flowing 150 gpm via the drain. OR reverse the check valve on the FDC, connect hoses to the FDC and to a hose monster, and flow water, the same gpm as the required sprinkler flow, what do the calibrated gauges say on the riser? If it is the same you are OK, if more OK if less the contractor has a problem!

Bucket test, no way!
 
Thanks for the replies.

This system has not been finaled so we still need to do the rooftop flow test, etc......

I am having the contractor provide me with the latest calcs (misplaced with my set of plans).....allegedly the system does have a 10% safety factor and appears the bulk mains have been upsized as well.....so I am leaning towards not requiring further testing.

Thanks for the help
 
two years is too old for my liking..

on the positive side you can now observe the piping install and compare to the calcs. Sure they upsized the pipes, but how many elbows and bull tees did they add.

If the calcs don't match the installed system, have them recalc based on actual install conditions. If they then have a 10psi cushion you could feel somewhat comfortable.
 
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Tim - What is a reasonable time from flow test to final inspections? 6 months? 12 months?

If they finished construction in 3 months, and the installation matches the plans and calcs, do you accept it as is? What kind of confidence do you have in the water supply?
 
RBK our water authority will only guarantee 25psi even though you have 62 at the riser. I imagine most (all) water districts have a minimum guarantee. Since we are allowing the designer to use the pressure that is reasonably present, I don't think it is unreasonable for them to reciprocate with a flow more current than 2 years.

How much confidence? Not much. The recorder has seen pressures as low as 32 where it is typically 60.

I have also been there when the water authority dug up the 8" main only find a 20' gap spliced with 4" (they extended the main from each end, replacing the old 4", but never actually connected the 8").

A lot can happen in 2 years; it has to be compliant when I issue a [edit]permit[/edit], not 2 years ago. Not to say the flow test has to be done the same week, but depending on what work is being done in the area I am typically satisfied within a year.

Just to be clear, the flow was 2 years old when the plans were submitted?
 
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Just reread OP and I am not sure what exactly the scenario is, but let me say how I handle it..

When you submit the flow has to current, and it has to be the closest hydrant. I don't accept 2 blocks away. They think I'm a pain but I have seen too many crazy things to trust that what you get two hydrants away is the same as at the site. It took 4 guys two days to figure out how to shut a main off so the fire main could be cut in! I don't trust their maps to be accurate.

After construction is completed I get a report of testing per NFPA 25 (I personally like the ASA forms and that is what I ask for). As long ast he static/residual from the test is above the calculated demand, all is well in the universe.

If you had a current flow and it took two years to complete the building, then that's not an issue. Getting another flow doesn't change anything (too late for that to be of any use); the pressures at the riser will tell you what you need to know.
 
cheyer said:
Thanks for the replies.This system has not been finaled so we still need to do the rooftop flow test, etc......

I am having the contractor provide me with the latest calcs (misplaced with my set of plans).....allegedly the system does have a 10% safety factor and appears the bulk mains have been upsized as well.....so I am leaning towards not requiring further testing.

Thanks for the help
Click to expand...
Perfect, look at the calculations and see what psi you need at the base of the riser. Use a calibrated gauge and flow XX gpm what ever the demand is off the roof and read the residual pressure on the gauge while flowing XXX at the roof. If it matches or better then great, if not time to start replacing pipe that is bigger. You do not need a hydrant flow if you do this.

Problem solved :)
 
hydrant flow is going to change as other development occurs..

You're worried about 12 heads? try thousands some time.
 
So we have a sprinkler and or standpipe system designed around a water supply that fluctuates perhaps a lot. They design a fire protection system on this water supply. Which is based on someone holding a pitot blade in a stream of water flowing, hopefully using a calibrated gauge, that is rock steady when they take the reading. They then use this number to calculate the flow, hopefully they use the correct "C" for the hydrant they tested and did the math correctly. They then put this information into a computer that calculates the pressure demand to 56.90 psi. Do you see where I am going with this??

Taking this into consideration this is what NFPA 13, 2010 ED. says about all this. So 10% safety cushion OK???

A.23.2.1 Care should be taken in making water tests to be

used in designing or evaluating the capability of sprinkler systems.

The water supply tested should be representative of the

supply that might be available at the time of a fire. For example,

testing of public water supplies should be done at times

of normal demand on the system. Public water supplies are

likely to fluctuate widely from season to season and even

within a 24-hour period. Allowance should be made for seasonal

or daily fluctuations, for drought conditions, for possibility

of interruption by flood, or for ice conditions in winter.

Testing of water supplies also normally used for industrial use

should be done while water is being drawn for industrial use.

The range of industrial-use demand should be taken into account.

In special situations where the domestic water demand

could significantly reduce the sprinkler water supply, an increase

in the size of the pipe supplying both the domestic and

sprinkler water can be justified.

Future changes in water supplies should be considered. For

example, a large, established, urban supply is not likely to

change greatly within a few years. However, the supply in a

growing suburban industrial park might deteriorate quite rapidly

as greater numbers of plants draw more water.

Dead-end mains should be avoided, if possible, by arranging

for mains supplied from both directions. When private fire

service mains are connected to dead-end public mains, each

situation should be examined to determine if it is practical to

request the water utility to loop the mains in order to obtain a

more reliable supply.
 
OK.. I guess that's why I've seen fire pumps in a 3 story building...

Just because I have 60 psi street pressure today, when my project delivers... who tells me that the street pressure is now 25 psi because of the new building across the street?

No one..
 
TimNY,

The most current test flow info. was approximately two years prior to the permit being pulled......they are looking at a couple months away from completion......late 2007 was the report date....early 2011 office building to open.

IE,

That's exactly what I was thinking...thanks

Peach,

the 12 heads is only the MRA...not the total head count
 
This will help moving forward...(not sure if this was in 2002 ed.)

22.2.1.1* Where a water flow test is used for the purposes of system design, the test shall be conducted no more than 12 months prior to working plan submittal.

Out of 2010 ed. of NFPA 13.........I now have to make my water dept. aware of this so they may need to change their operations a bit
 
should, probably, permit guy... it kind of depends on the FD/water authority to flow the hydrants, doesn't it? Every time a new project comes up that depends on the water source, it's going to affect my pressure.
 
Just as an example - Building was designed in early 90's. Flow test was done incorrectly. Fire pump was over-sized. Now the the main pressure is more than expected and total head pressure downstream of the pump is ~250 psi. Guess what the water supply pipe into the building had Megalug type connections, so if the bolts are not torqued correctly the pipe separates. And now they are reworking that wing of the building due to an unknown water leak under the concrete slab originating at or near the pump room.

Second example - Building is converted into a Big Box Store. Water flow test is conducted and system designed. Two years later a change in the building requires an addition to the sprinkler system. Water flow test is done and water supply is about half the pressure. Oops. Original water test was not done correctly, street isolation valves found closed through several city blocks (contractors working on water lines). New design now requires fire pump. Oops.

Water flow tests are good when done correctly. But the tests have to be done during peak usage or data has limited value. Testing at night or in off peak hours renders a faulty test. Flow test devices can be used even during traffic times where the stream has a diffuser after the location for the reading.
 
P.S. Bucket tests should only be done on 13D type systems to prove adequate flow on one head. Bucket should be a barrel. This type of test does not work on larger systems.
 
FyrBldgGuy said:
Just as an example - Building was designed in early 90'sSecond example - Building is converted into a Big Box Store.
Click to expand...
It does provoke a good question..

As mentioned before, a FM in a neighboring jurisdiction saw 32psi on a circular chart recorder where normally it is about 60. So we know in real life, at some point, the pressure dropped 28psi.

Upon questioning the water authority, they respond that they only guarantee 25psi.

So the question is, what do we design to? Do the flows even matter?

If the water authority guarantees a minimum level of service, does it matter? Should we be designing to the minimum level of service?
 
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TimNY said:
If the water authority guarantees a minimum level of service, does it matter? Should we be designing to the minimum level of service?
Click to expand...
In most areas I would say that it is unnecessary and cost prohibitive. I think it depends on the reason for the pressure fluctuation. Was there a sudden increase in demand from a large fire, or was there a main break a few blocks away? Is the pressure subject to fluctuation with resevoir levels and it hasn't rained in a while? Most water departments won't "guarantee" much more than about 20 psi, but their normal opperating range is typically much higher. If drops into the 25 psi range are common, or occur rarely but for extended periods of time (such as a drought), the fire department should take a close look at their policy, and maybe using the minimum level is appropriate.

The City of Fresno doesn't work on the typical flow tests. They have 3 design curves, depending on the size and length of the main and if it is looped or dead end. The best curve provides for 45 psi static @ 1800 gpm and the worst 40/25@1350. I don't recall a project I have done there where I didn't need a fire pump, and the static pressure at nearby hydrants is typically around 50-55 psi. The fire department has been aware of the pressure issues for years, and adopted this policy to ensure the sprinkler system would work as designed.
 
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