Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Landscaping & Lawn Care

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 07-29-2009, 06:20 PM   #1
Newbie
 
Join Date: Jul 2009
Posts: 1
Share |
Default

Any sprinkler contractors? Fluid dynamics engineers? Help determine water pressure


Setup:

Pressurized irrigation system. 1 1/2" service line, gravity fed, ~20psi.

I added a 1/2 hp booster pump and reduced the line to 1 1/4". At the end of the 300' "main line" (which is 1 1/4") I measured the flow:

~15 gpm

I then turned on the 1/2 hp booster pump and measured the flow

~20 gpm

Question: What do you think the pressure is if I restrict the output to 13gpm (which is the size of the largest sprinkler zone I am planning to install). I would like to see a minimum of 45psi -- but since I am a mere mathematician and not too well versed in Bernoulli's Principle I figured I throw it out to the wise engineers.

jordansrt is offline   Reply With Quote
Old 07-30-2009, 01:52 PM   #2
Member
 
Join Date: Apr 2008
Location: Northern NJ
Posts: 208
Default

Any sprinkler contractors? Fluid dynamics engineers? Help determine water pressure


I'm not smart enough to answer that, but this might help:

http://www.irrigationtutorials.com/index.htm

cgoll is offline   Reply With Quote
Old 07-31-2009, 06:13 PM   #3
Don't know it all, yet!
 
Join Date: Jun 2008
Location: Metro Atlanta, GA
Posts: 910
Default

Any sprinkler contractors? Fluid dynamics engineers? Help determine water pressure


If you have a six inch line at pressure A, and then reduce that line down to two inches, the pressure will still be A. The difference will be how much flow (gpm) comes out of the two inch line versus the six inch line. If you can get 20 gpm at the end of the line at your value of 45 psi, then one 13 gpm head will work fine and the pressure will still be 45 psi. If you put two 13 gpm heads on that line, then you will need to increase you delivery capacity to 26 gpm- either by increasing line pressure or supply line diameter. What will happen is that at the same 45 psi, with two heads requesting 26 gpm total you will only get about 10 gpm to each head, assuming that they are equidistant from the pump. In reality, most likely the closest one will get a little more pressure, and subsequently a slightly higher output.

Or, you could just put a pressure gauge on the line.
__________________
If it's worth doing, it's worth doing right. If you wouldn't put your name on it, it ain't done right!

Last edited by downunder; 07-31-2009 at 06:25 PM.
downunder is offline   Reply With Quote
Old 07-31-2009, 08:29 PM   #4
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Default

Any sprinkler contractors? Fluid dynamics engineers? Help determine water pressure


Quote:
Originally Posted by jordansrt View Post
I figured I throw it out to the wise engineers.
Showing real wisdom, they are throwing it back
http://www.engineeringtoolbox.com/fl...nics-t_21.html
http://www.engineeringtoolbox.com/da...ion-d_646.html
http://www.engineeringtoolbox.com/pr...pes-d_404.html


As a sanity check,
HP ≈ GPMxHD/(40xEfficiency)
e.g., 100x120'/[40x50%] = 6.1 hp, depending on the efficiency of the pump you select.
Pump efficiencies range from 15% to over 90%.

That Bernie guy says that 14.7 psi ≈ 33' of head.

Would you post a diagram of your before and after setup, showing pipe lengths, pump location and relative heights, along with a link to your pump spec's and curve?

Last edited by Yoyizit; 07-31-2009 at 09:26 PM.
Yoyizit is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Low hot water pressure crebive Plumbing 38 02-26-2013 12:26 AM
Water pressure dropping tucsoncop Plumbing 2 04-25-2009 12:19 PM
Low water pressure upstairs but gauge reads 100psi? rivers72 Plumbing 7 11-15-2008 07:55 PM
Water pressure issues - in one part of the house stream41 Plumbing 4 11-11-2008 07:43 PM
New Help With Improving Water Pressure hayhursm Plumbing 1 01-31-2006 06:55 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.