Register free!


Reply
 
Thread Tools   Display Modes
  #21  
Old 08-30-2011, 12:56 PM
Kiril Kiril is offline
LawnSite Fanatic
 
Join Date: Jun 2007
Location: District 9 CA
Posts: 18,318
This is an issue of both pressure and time .... pressure drop downstream of the PVB and time required to fill the irrigation mains & laterals. Let's assume he is using a Febco PVB, which starts to dump when downstream pressure falls below 5 PSI (i.e. the air inlet poppet requires 5 PSI to seal properly) and will fully open at 1 PSI downstream pressure per specs. The goal here is to maintain downstream pressure above 5 PSI until the pump kicks in.

In addition to a slow opening master valve (or as a possible alternative), another way you could potentially do this is to maintain a "leak proof" system by first making sure you aren't getting any low head drainage (i.e. use sprinklers and drip lines with check valves). The more water/pressure you can keep in the irrigation mains and laterals between irrigation events, the less water/pressure and time it will require to bring the downstream lines back up to operating pressure and flow.
Reply With Quote
  #22  
Old 08-30-2011, 12:58 PM
Wet_Boots's Avatar
Wet_Boots Wet_Boots is online now
LawnSite Fanatic
 
Join Date: Mar 2005
Location: metro NYC
Posts: 40,674
this problem isn't solved until we nick the homeowner for an additional thousand dollars
Reply With Quote
  #23  
Old 08-30-2011, 01:06 PM
Dirt Boy's Avatar
Dirt Boy Dirt Boy is offline
LawnSite Senior Member
 
Join Date: Dec 2005
Location: Nebraska
Posts: 454
Quote:
Originally Posted by Kiril View Post
A slow opening master valve may allow the system to lose enough pressure to kick the pump on but not cause the backflow to dump.



I thought you said there was no pump relay?
Don't mean to confuse you, there is a pump relay, but it is not turned on by the sprinkler controller. It is turned on by the pressure switch at the very small pressure tank.
Thus, by the time that pressure switch "sees" low pressure and activates the pump, the main line pressure has dropped significantly and the PVB pops open.
Reply With Quote
  #24  
Old 08-30-2011, 01:13 PM
Wet_Boots's Avatar
Wet_Boots Wet_Boots is online now
LawnSite Fanatic
 
Join Date: Mar 2005
Location: metro NYC
Posts: 40,674
what are the pressure switch settings?
Reply With Quote
  #25  
Old 08-30-2011, 02:10 PM
Dirt Boy's Avatar
Dirt Boy Dirt Boy is offline
LawnSite Senior Member
 
Join Date: Dec 2005
Location: Nebraska
Posts: 454
Not sure, it just has settings you can choose 40, 50, etc. right now it's at 60
Reply With Quote
  #26  
Old 08-30-2011, 03:05 PM
stebs stebs is online now
LawnSite Member
 
Join Date: Jun 2010
Location: Eastern KS
Posts: 181
What if you had a very small zone such as a small drip zone or just a couple heads as the first station in the lineup? Just enough to slowly bleed down the pressure and get the pump running, but big enough to keep the pump running.
Reply With Quote
  #27  
Old 08-30-2011, 03:43 PM
Dirt Boy's Avatar
Dirt Boy Dirt Boy is offline
LawnSite Senior Member
 
Join Date: Dec 2005
Location: Nebraska
Posts: 454
Quote:
Originally Posted by stebs View Post
What if you had a very small zone such as a small drip zone or just a couple heads as the first station in the lineup? Just enough to slowly bleed down the pressure and get the pump running, but big enough to keep the pump running.
Thought of that, basically doing what Kiril suggest, just different way
Reply With Quote
  #28  
Old 08-30-2011, 06:07 PM
bcg bcg is offline
LawnSite Bronze Member
 
Join Date: Mar 2005
Location: Tx
Posts: 1,779
You guys sure are devoting a lot of effort to fix a PVB that's working exactly as designed. As long as the PVB was installed correctly (somewhere that the dumping water isn't an issue), leave it alone. This reminds me of NASA spending millions of dollars to develop a pen that would work in zero gravity while the Russians chose to use a pencil. Sometimes the pencil is really the better solution.
Reply With Quote
  #29  
Old 08-30-2011, 06:28 PM
FIMCO-MEISTER's Avatar
FIMCO-MEISTER FIMCO-MEISTER is offline
LawnSite Fanatic
 
Join Date: May 2007
Location: Red State America
Posts: 18,701
On a subject similar to this. How would a well on a pressure tank cause water hammers at startup and during zone changes? All the piping allows for 5fps. It cycles every 45 seconds if that means anything.
Reply With Quote
  #30  
Old 08-30-2011, 06:32 PM
AI Inc's Avatar
AI Inc AI Inc is offline
LawnSite Fanatic
 
Join Date: Dec 2007
Location: Southern NH
Posts: 22,095
Pete, if its cycling every 45 seconds , its not using enough water. Between the cycling and the water hammer I would guess that ya have bucu water and are not using all that much of it.
__________________
Reply With Quote
Reply

Thread Tools
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

Forum Jump






Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ©1998 - 2012, LawnSite.comô - Moose River Media
All times are GMT -4. The time now is 04:58 AM.

Page generated in 0.09084 seconds with 7 queries