Why Would Height of Tank Return Water Matter?

7/21/2023

I recently heard of an incident where the fire water return from a flow meter on a fire pump was connected low from a tank and it did not work appropriately. So as a solution they decided to connect it high on the storage tank a and somehow this configuration fixed the issue.

Both connections would have the same head due to elevation so it does not make sense to me why one would work but not the other.

Why does it matter if you connect a return loop to a fire water storage tank near the top of the tank rather than near the bottom?

Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe

4 Comments

Pete H

7/21/2023 07:02:06 am

But doesn't the hydrostatic pressure at the bottom of the tank increase compared to the pressure at the top of the tank?

I don't know your exact situation, but if the reason it didn't work properly was too much velocity pressure outdid the listings of the fittings... this might just outright relieve that pressure to a situation that works properly.

Take with a grain of salt, this is even more of a shot in the dark than my normal posts.

Dan Wilder

7/21/2023 08:32:31 am

The flow meter should have no issue on location of the return line. The longer line may need to be upsized due to length per 20-22' 4.22.3.4

A test header downstream of the flow meter shouldn't be installed at a higher elevation as it will affect the readings.

A pressure relief valve would have issues as they do not like having backpressure on the discharge side (MFG install say to avoid this).

Franck

7/21/2023 06:18:49 pm

It is probably related to the perturbations created close to the pump suction intake when water is coming back to the tank.
This is not an issue during normal operation (in case of fire) as you have a (anti-)vortex plate, but when you make the test this may greatly affect the proper operation of the pump with turbulences at the intake.
Thus, normally, having the water back to the tank at the higher possible level.
In Europe, we always design the return loop at the higher possible elevation to avoid these turbulences (or at least, as far as possible from the pump suction line).

Jesse

7/25/2023 07:58:10 am

Its hard to see how this was an issue unless as Franck said, the return inlet caused turbulence at the pump suction.

Leave a Reply.

Home
Our Cause

The Blog
The Forum

PE Exam Prep
The Toolkit
MeyerFire University

Pricing
Login
Support
Contact Us

MeyerFire.com is a startup community built to help fire protection professionals shine.
Our goal is to improve fire protection practices worldwide. We promote the industry by creating helpful tools and resources, and by bringing together industry professionals to share their expertise.

MeyerFire, LLC is a NICET Recognized Training Provider and International Code Council Preferred Education Provider.
All text, images, and media Copyright © 2016-2024 MeyerFire, LLC

We respect your privacy and personal data. See our Privacy Policy and Terms of Service. The views, opinions, and information found on this site represent solely the author 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.

Discussions are solely for the purpose of peer review and the exchange of ideas. All comments are reviewed. Comments which do not contribute, are not relevant, are spam, or are disrespectful in nature may be removed. Information presented and opinions expressed should not be relied upon as a replacement for consulting services. Some (not all) outbound links on this website, such as Amazon links, are affiliate-based where we receive a small commission for orders placed elsewhere.

Why Would Height of Tank Return Water Matter?

Leave a Reply.

ALL-ACCESS

SUBSCRIBE

COMMUNITY

YOUR POST

PE EXAM

FILTERS

ARCHIVES

PE PREP SERIES