Flowmeter Separation Distance Include Fittings?

2/7/2020

Split case pump - flow meter installation question:

As indicated in NFPA 20, the distance from the flowmeter to either isolation valve should be as recommended by the meter manufacturer.

Based on your own experience, do fittings (elbows or bends) need to be included in this distance calculation?

For example - should the distance recommendation length of 10-diameters be calculated from the last fitting or is the fitting ignored and only calculated from the isolation valve? Thank you.

Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe

3 Comments

Dan Wilder

2/7/2020 10:13:54 am

That minimum distance is in reference to the length minimum of STRAIGHT pipe, as based on 2 or 5 diameters of pipe before and after the flow meter. If you meet that minimum, the configuration outside of those minimums isn't an issue with that type of flow meter. In this case, the butterfly valve disc is the point measured (center of the valve) but if you were to have an elbow or tee (changing water direction), that point would be from the start of STRAIGHT pipe, not the center of fitting.

Good practice would be that you minimize the supply side turbulence as much as possible but after the valve should not be near as much an issue.

Mike L

2/7/2020 11:41:04 am

Agreed with Dan's response. The minimum pipe length before and after the flow meter is the straight length provided to allow the water to return to laminar flow and get a more accurate reading on the meter.

Mike

2/9/2020 09:52:44 pm

It's best to have laminar flow so the meter reads accurately. It's even better to use two valve - inlet that is required and downstream that is suggested.

Then fully open the upstream valve and use the downstream valve to throttle flow for the most accurate reading.

This suggestion was given to me by a pump manufacturer and makes a lot of sense.

Free Signup

Subscribe and learn something new each day:

Community

Thank You to Our Top December '19 Contributors!

1. Mike
2. Sean
3. James
4. Mike L.
5. Wayne A

6. Marc V.
7. Colin L.
8. Alfrid
9. Vinnie
10. Marina A

Your Post

SUBMIT A QUESTION

The Toolkit

Sprinkler Designer or Engineer?

Get all of our tools, including the Sprinkler Database, Friction Loss Calculator, Fire Pump Analyzer and more:

FREE 30-DAY TRIAL

GET THE TOOLKIT

Filters

Exam Prep

2019 PE Prep Guide
(Available Now!)

PE Prep Series
(Available Now!)

Current Leaderboard
(Click to enlarge)

PE Problems

Visit July-October for daily Fire Protection PE Exam sample questions.

Solutions are posted the day after posting.

Comment with your solutions, questions or clarifications.

Please note that questions posted are unofficial and in accordance with NCEES rules are intended to be similar to actual exam questions, not actual exam questions themselves.

RSS Feed

Home - About - Blog - Contact - Exam Prep - Store

Copyright © 2020 MeyerFire, LLC
The views, opinions, and information found on this site represent solely the author shown and do not represent the opinions of any other party, nor does the presented material assume responsibility for its use. Fire protection and life safety systems constitute a critical component for public health and safety and you should consult with a licensed professional for proper design and code adherence. Some (not all) outbound links on this website, such as Amazon links, are affiliate-based where we receive a commission for orders placed elsewhere.