Calculating flow through a pipe 1

[Slickstir]

I've been asked to add a 6" steel drain pipe to a water tank that is open to atmosphere. The drain pipe will come straight out of the tank after a gate valve for approximately 15ft and then discharge to a ditch (no elevation change before discharge).

What is the calculation to estimate the flow out of the drain pipe when the tank level is only 1.5 feet above the pipe? They were hoping a minimum flow of 500GPM but I was wondering if they would need a larger pipe for that amount of flow at the end of the drain.

 

[RVAmeche]

It's pretty basic, see Crane TP #410 or Cameron Hydraulic Data.

If you're looking for how the flow changes with varying tank level, a transient calculation is a bit more complicated.

 

[LittleInch]

No 6" is good.

The tables here for 6" steel pipe ( scroll down to the 6" tables) have 500 gpm at about 1.6 ft/ 100 ft, so if your pipe is only 15ft long then you should be good even if you add in some losses for the exit losses and other losses.

https://www.engineeringtoolbox.com/pressure-loss-steel-pipes-d_307.html

For higher heights of water you might get a lot more than 500 gpm.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[RVAmeche]

See this link for a basic tank flow equation
Vessel Flow

 

[Slickstir]

Thanks!

 

[Latexman]

The nameplate should say "Designed by SGOTI".

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[racookpe1978]

SGOTI?

I missed that one.

 

[RVAmeche]

some guy on the internet