Calculating gpm

   / Calculating gpm #21  
thanks -- guess we wuz typing at the same time--
mike
 
   / Calculating gpm #22  
Yes, we wuz!!

$110 for the class..
 
   / Calculating gpm
  • Thread Starter
#23  
Boy, this post has just turned to @#%!! Just kidding :)

Mikim, That engineering question is loaded with variables (problems to solve), whew!

John4NH, the ETA I was talking about is like what Bird described.

A lagoon is a square pond about 5' deep by 25' x 25' to 50' x 50' ( at the bottom) depending on daily flows and evaporation rates. Has a 3' run to 1' rise from the bottom to the top of the 2' berm surrounding the pond. So you have a total of 7' of depth, but about a three to five working area. Still has a septic tank to perform the anerobic action and uses wind and aglae for the aerobic action in the lagoon. They are somewhat common around my area. Have never smelled one stinking. Projected to have a fifty year life span. I think these are the cheapest system avail in my area. And is what the DEQ guy recommends. About less than 2,500 and only maintainence is to mow around lagoon and pump the septic tank as needed. ( suggested yearly).
 
   / Calculating gpm
  • Thread Starter
#24  
Oh yeah, I could do a ETA or Lagoon myself and DEQ will come inspect. Septic tank $600-$800 plus some pvc. Maybe I could justify a bigger tractor and a backhoe with water line, electric line, septic system, basement and footings to do? I really need a bigger tractor for other things, so just need to justify the hoe... Sounds better all the time.
 
   / Calculating gpm #25  
<font color=blue>pump the septic tank as needed. ( suggested yearly)</font color=blue>

Pumping out the septic tanks is another topic./w3tcompact/icons/wink.gif Several years ago I was doing a gas leakage survey in Sayre, PA, and read an article in the local newspaper that I found interesting. The city had extended their sewer lines into an area that had apparently been recently annexed into the city and wanted the residents out there to abandon their septic systems and connect to the new sewer line (at the residents' expense of course) and they ran into some rather vocal opposition because of the cost to tie into the city sewer. I don't know the end result, but the city wanted to agree to let them continue using their septic systems, but with an ordinance to require them to have the tanks pumped at least every two years if they did that.

When I had my aerobic system installed, I thought I'd just have it pumped every two years to make sure I never had a problem. My service company said, "Fine, if you want to waste the money, but we'll tell you when it needs pumping." So . . ., they told me; a week ago today, and I had it done; just under 4.5 years, and they said it shouldn't have needed it that soon, but they suspect my wife of using too much bleach in the laundry./w3tcompact/icons/frown.gif

Bird
 
   / Calculating gpm #26  
Gary.

<font color=blue>AH I think I just found it. </font color=blue>

I think you did to Gary, good job. You will be a Fluid Dynamicist by dark, next thing ya know you'll be asking about Reynolds numbers./w3tcompact/icons/smile.gif
2.31 ft/psi is a pretty good number.
Al
 
   / Calculating gpm #27  
For structure work, figure 100gpm minimum on a single nozzle, at a minimum 100psi. For wild land, figure starting with a variable flow nozzle set at 35-40gpm at first, and then adjust for fire conditions, and figure about 100psi. I would conservatively say MAYBE two wild land nozzles on that one line.

I would check with your local fire dept. they can give you more details on particulars for your area.

If you could really flow 100gpm though, that would be pretty good! Not only could it allow you to put serious water down, it would also allow some good refill capability for a fire engine.

Remember though, before you try to fight fire, there's safety equipment and training too...

RobertN in Shingle Springs Calif
 
   / Calculating gpm
  • Thread Starter
#28  
RobertN, thanks for the numbers. Once I figure out the flow I will research more. I didn't realize the amount of water pressure needed. I thought 100 gpm would be plenty. If I can get 100 GPM, I think it will be around 45-50 psi. Still too early to tell.

Al,... boy you made me do my homework! You lost me on that last number. But I have been researching the Reynolds number. Determines type of flow, laminate Re < 2300 or turbulent Re > 3400 (I think) or transitional if in between the two. If flow is laminate, a lot more friction is present do to the shear forces. If I kept all the terms in the right measurements I came up with around 680.

Re = pipe dia (l) x velocity (v) x fluid density (p)/fluid viscosity (n)

l = sch 40 3" pvc = 3.042"
v= 4.40 to 4.70 fps ( I tried a couple formulas and got different results)
p= 62.41lb/cubic ft @ 50 degrees Fah
n = 1.308 @ 50 degrees Fah

So flow is laminar, correct, maybe...

Time for Darcy coefficient of friction, f=64/Re and the

Darcy formula = density x f x length x velocity squared/2 x diameter......???????

So will the darcy formula give a better indication of the anticipated flow?

I know I jumped ahead of the teacher!... and am probably on the wrong track.
 
   / Calculating gpm #29  
<font color=blue>Posted by Chillimau (Bronze Member)
Posted on 10/24/01 08:18 PM</font color=blue>

8:18 PM What time does it get dark at your place? I think I got it "Fluid Dynamicist by dark"

Gary, the 2.31 ft/psi is found by dividing a square foot of area (144 sq inches) by the density of water (62.4 lbs/Cubic foot)

In your case a head loss of 39.8 ft is a pressure loss of 39.8/2.31 or ~ 17 psia.

Al


<P ID="edit"><FONT SIZE=-1>Edited by twinkle_toes on 10/25/01 02:24 PM (server time).</FONT></P>
 
   / Calculating gpm #30  
Hey Bird, forgot I added to this post. I did not realize he wasn't irrigating. I irrigate with over 100 Rainbirds (not at one time) I don't have a meter. I'm on a well but I don't irrigate with well water. Here in the fruit basket capital we have irrigation canals. I order 3 miners inches of water from April 15th to October 15th. A miners inch is just over 11 gpm. I'm also on a party line. At any one time with no one irrigating, we have about 140 gpm at 120 psi available. No pumps are required, its all gravity fed. California is littered with all sorts of water projects especially with the Sierra Nevadas to the East and Cascades to the North. Between the Sierras and the Cascades, you won't find higher snowfall totals anywhere in the US. The snow makes a great reservoir. Rat...
 

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