When are hydraulic calculations required?

8/24/2017

For small building renovations, when do you (as a review engineer or AHJ) require hydraulic calculations to be provided?

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11 Comments

Mark link

8/24/2017 08:03:00 am

If the hazard of the occupancy is increasing and therefore requiring sprinkler to be re-calculated or if the existing sprinkler system is being modified in any way that the original design is no longer valid

Eric

8/24/2017 09:02:32 am

Occupancy change, system modifications, size of renovation. If it is a small renovation (of say 10 sprinklers), no occupancy change and the heads are just relocated one for one (i.e. for spacing purposes or a new ceiling), it may not be worth the calculation. Depends on your comfort level.

Mark Ma

8/24/2017 09:32:43 am

In all SF bay area cities, if any TI project involve using a flexhead connection in the fire sprinkler system, a hydraulic calculation will be required.

Bobby

8/24/2017 06:28:15 pm

Calculations required when the sprinkler renovations exceed what the original system was designed for. This includes:
1. If the sprinkler renovations now include numerous "2-fers" (2 sprinklers supplied by one outlet), that were not present before.
2. Additional sprinklers added on existing branch lines, in which it is obvious that a calculation may prove more demanding than the original design.
3. Increase in occupancy hazard classification.

Nimal Tissa Wijetunga

8/25/2017 04:13:59 am

Hydraulic Calculation is required except Pipe Schedule method.

Sam

8/25/2017 10:39:58 am

Hydraulic calculations are required due to renovations:
1- change in hazard classification
2- change in hydraulic remote area that may impact the existing pipe sizes, static & residual pressures of an existing sprinkler piping system.

JOHNATHAN

1/4/2019 07:23:31 am

I love how people are only stating opinions and no one quotes the standard. I wouldn't validate any of the responses unless I am provided with a Code Section

Heber Cuellar

4/13/2020 07:46:26 am

Hello Jonathan,

Did you ever get a (NFPA) code reference?

Haus Douglas

7/16/2020 11:53:14 am

There is no section in NFPA 13 or elsewhere telling you when to re-calculate. All of the above answers are correct in the sense that ultimately it's a prudential judgement based upon many factors.

Thomas Bender

1/28/2021 01:08:17 pm

According to NFPA 13 (2013 and 2016 editions): the section dealing with modifications to existing hydraulic systems is:
8.15.20.5 Revamping of Hydraulic Design Systems. The requirement is to determine if the system design flow rate will be achieved. The Annex material states "It is not the intent of this section to require a full hydraulic analysis of the existing piping system in addition to new sprinkler layout".

NFPA 13 - 2019 edition moved the modification of existing sprinkler systems into a new chapter, Chapter 29, with 29.5 covering the "Revamping of Hydraulic Design Systems", but of note, all of the Annex material dealing with modifying existing systems has been removed.

Therefore, moving beyond the 2019 edition, hydraulic calculations may be required for all system modifications. That's my 2 cents.

Andrew MacLean

7/18/2023 10:07:26 am

8.15.20.5 is specifically looking at requirements for goose necks. Essentially looking at going from Upright to Return Bends. It means if you can prove there isn't a significant system loss from the goose necks you don't need a full new hydraulic calculation on the system refit.

It does not encompass all modifications to existing systems.

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When are hydraulic calculations required?

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