## Calculating Water Flow Rates

## Calculating Water Flow Rates

(OP)

Hello and sorry for what I think is a dumb question, but I was unable to find what I am looking for elsewhere, then I thought you guys could easily help me here.

I am trying to calculate what the flow rate from a water service should be. I know that the simple formula is Q=AV (flow rate = area times velocity), however I do not know velocity. What I do know is that the service is 1 inch polyethylene, and the pressure of the main tested from a very close hydrant to the service is 66psi, and the service length is 20 feet. What is the formula to calculate the flow rate from the end of that service? I feel like I am missing something simple here, but I am unsure what...

Thanks for any help you guys can provide, :)

I am trying to calculate what the flow rate from a water service should be. I know that the simple formula is Q=AV (flow rate = area times velocity), however I do not know velocity. What I do know is that the service is 1 inch polyethylene, and the pressure of the main tested from a very close hydrant to the service is 66psi, and the service length is 20 feet. What is the formula to calculate the flow rate from the end of that service? I feel like I am missing something simple here, but I am unsure what...

Thanks for any help you guys can provide, :)

## RE: Calculating Water Flow Rates

Reasonable Velocities for the Flow of Water through Pipe:

Boiler Feed.............8 to 15 ft/sec

Pump Suction ............4 to 7 ft/sec

General Service.........4 to 10 ft/sec

City.......................to 7 ft/sec

Transmission Pipelines...3 to 5 ft/sec

Go to a basic hydraulics book. Try Cranes Technical Paper 410 as a reference for the above velocities.

http://www.eng-tips.com/viewthread.cfm?qid=111206

http://www.amazon.com/Fluids-Through-Valves-Fittin...

## RE: Calculating Water Flow Rates

bimr is right in what he says if you are looking for general guidance.What i would like to know is why is this important in this case? If you really want to know and you dont have a meter simply use the line to fill a bucket of known volume and record how long it takes. That will give you Q and you already know A so then you can calculate V.

Regards

Ashtree

"Any water can be made potable if you filter it through enough money"

## RE: Calculating Water Flow Rates

## RE: Calculating Water Flow Rates

Sorry for taking a bit to get back to this. Thanks for the links and info provided. I will check them out.

I am not sure off hand of the dr of the poly, but I was given this info in the attachment if it helps.

RConner, I guess full bore discharge is what I am looking for. Although I realize the tubing would not be straight (somehwat snaked in ditch) and there could be other minor headloss associated; full bore potential. Just curious, would there be much flow throttle through a fully opened curb stop?

Ashtree, the barrel fill method was done however months later now, there are discrepancies between the guys who remember what the results were and the documentation is lost.

## RE: Calculating Water Flow Rates

Richard A. Cornelius, P.E.

WWW.amlinereast.com

## RE: Calculating Water Flow Rates

Once you have iterated all that, I have noticed that the site at

http://www.engineeringtoolbox.com/water-discharge-... contains a chart that reports if you instead had 100 feet of 1" hose it apparently would discharge about 50 gpm at the far end with 60 psi at the supply. I've also seen various sites and calculators that say on the other hand the flow through just a leak hole or aperture in a pipe with area due to 1" diameter in a 60 psi pipe discharging to zero pressure would flow in the much greater range of say 160-200 gpm. Therefore, If you do your calculations properly, you may well have a result somewhere in-between these numbers (with your much lesser length of piping).

While my earlier question related mostly to what you had at the end of your 1" pipe (was there some sort of premise plumbing at the end of the 20 feet, or just an open jet etc as you have answered), yes, due to extreme velocity of the full-bore discharge I believe even minor losses could be exaggerated. (and if I understood this situation correctly, I'm gonna make a wild guess there may be say a hundred gpm or so discharge, so you might need a pretty good-sized "bucket" for a meaningful flow test!)

## RE: Calculating Water Flow Rates

## RE: Calculating Water Flow Rates

## RE: Calculating Water Flow Rates

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

## RE: Calculating Water Flow Rates

Although if you have a water meter, it is non linear at higher flow rates.

Also in this case, minor losses will be significant.

http://www.epa.gov/water-research/epanet

Hydrae