|
|
What would cause a 10% reduction in the full flow residual pressure from the current main drain test, when compared to the original acceptance test or previously performed tests?
If the original acceptance test or previously performed test information is not available, then the residual pressure on the current main drain test must be within 5 PSI of the design/demand pressure. What would cause a decrease over time? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
11 Comments
Pete H
10/31/2023 06:39:49 am
Could be that the water supply got worse, there's an obstruction in the system, there's a forgotten a closed valve (this is one of the more likely options) or some other impairment.
Glenn Berger
10/31/2023 08:08:07 am
In addition to the statement that Pete made above, pipe deterioration can also have occurred.
Jesse
10/31/2023 08:11:04 am
I can think of numerous things. Degradation of water supply, a fully or partially closed valve somewhere, a physical obstruction somewhere upstream in the system, or heavier than normal demand on the system.
Dave
10/31/2023 10:37:45 am
Agreed, and maybe not as likely, but I've recently had cheap (as well as expensive, certified) gauges go bad. They can even get clogged.
Jack G
10/31/2023 08:18:31 am
I have run into situations where secondary fire flow pumps automatically set to turn on for a predetermined flow or pressure drop.
Tim D
10/31/2023 08:25:35 am
The way we approach this is we perform a hydrant flow test to verify city water supply has not changed. If we get a good test we ask the city to come out and re-core the tap off of the city main. That usually fixes the problem. If that doesn’t work then we go to the time and labor intensive option of replacing the main.
Eric R
10/31/2023 08:31:38 am
Pete has covered all the potential real causes if an actual degradation has occurred, but the number one reason we see when performing inspections for new customers is simply that previous main drain tests were not done correctly(or at all) and the residual pressure written on the tag was not collected with the main drain full open.
Eric R
10/31/2023 08:33:59 am
* "Pete and everyone else have covered all the real causes"
Inspector
10/31/2023 09:50:57 am
Woww!! That is crazy. Thanks so much for sharing. I love to hear success stories. It reminds us that all of the little things we do and enforce really do matter. :)
Thomas G. Kamprath
11/6/2023 08:24:50 am
It seems from the above comments about tags showing higher main drain test pressures, that many NFPA 25 inspectors are not doing their inspections properly or doing incomplete inspections. Leave a Reply. |
ALL-ACCESS
SUBSCRIBESubscribe and learn something new each day:
COMMUNITYTop October '23 Contributors
YOUR POSTPE EXAMGet 100 Days of Free Sample Questions right to you!
FILTERS
All
ARCHIVES
November 2023
PE PREP SERIES
|
RSS Feed
