Include Pressure Loss in Flow-Through CPVC Tee?

7/7/2023

Do you include a loss in your flow-through tees (the straight run) on CPVC for NFPA 13R or NFPA 13 Systems?

We're finding a loss through one software provider's default setting, whereas another by default does not include a loss on the flow-through CPVC tees. We'd like to find the correct approach.

Thanks in advance.

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11 Comments

7/7/2023 08:05:52 am

As per NFPA 13 23.4.4.7 (5) Do not include fitting loss for straight-through flow in a tee or cross.

So no, I do not include for the loss as it is not required by NFPA.

Ryan

7/7/2023 08:21:24 am

As per NFPA 13 (2013), 23.4.4.7(5) Do not include fitting loss for straight-through flow in a tee or cross.

As per NFPA 13R (2013), 7.4, Pipe Sizing, Piping shall be sized using hydraulic calculation procedures in accordance with NFPA 13, hence do not include the fitting loss for a straight-through tee or cross.

Alex

7/7/2023 08:23:26 am

Same as above, friction loss for straight-through fittings is not included

Dan Wilder

7/7/2023 09:51:17 am

NFPA 13 & 13R do not require flow through losses to be calculated.

13 - 2022-28.2.4.8.1(5) Losses for straight-through flow in a tee or cross shall not be included.
13R - 2022-8.2.1 (Procedure per NFPA 13)

NFPA 13D does require it for each of the 4 available methods (Simplified, Prescriptive, Hydraulic Calc, or MFG listed instructions)
13D - 2022-10.4.3
13D - 2022-10.4.2.3(6) Losses for straight-through flow in a tee or cross shall not be included.

Dan Wilder

7/7/2023 09:37:35 pm

****Corrected wording for NFPA 13D***

13D-2022-10.4.2.3(6) The system shall be hydraulically calculated in accordance with the provisions of NFPA 13, except that the friction loss straight through a fitting shall be included.

Jay

7/10/2023 08:57:43 am

This only applies to 1/2 inch piping in a network system though.

Ivan Humberson

7/7/2023 11:52:48 am

I maintain that, if the fitting equivalent lengths used in the hydraulic calculations are from the pipe manufacturer's specifications, then the pipe manufacturer's specifications must be used in their entirety, including counting fitting equivalent lengths for flow through couplings and the "run" of a Tee fitting when the manufacturer specifies equivalent lenghts for such - you can't "pick and choose" only a portion of the manufacturer's criteria. However, if the fitting equivalent lengths are based on the fitting equivalent length Table in NFPA 13 (and appropriately adjusted for internal diamenter and C-factor), then the loss for flow straight through a tee does not have to be counted.

Pete H

7/7/2023 12:36:47 pm

Not if you're calculating for NFPA 13 standards (as above has shown the reference from multiple helpful posters).

Ivan Humberson

7/7/2023 02:02:06 pm

If you're using the manufacturer's equivalent lengths instead of the Table in NFPA 13, then you are not calculating to NFPA 13 standard.

Pete H

7/10/2023 02:09:23 pm

Interesting, even if the manufacturer's specifications are listed for NFPA 13 use?

Janak Patel

7/12/2023 11:47:21 am

As mentioned by many commentators, the pressure loss through a straight pipe fitting should not be included because:
1. the 'length' is already included in the modeling i.e., a node to next node having a tee.
2. There is no change in the water 'flow direction' for a 'tee' fitting.

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Include Pressure Loss in Flow-Through CPVC Tee?

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