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I will add this.
A Home comp will blow out a sprinkler sys no problem .This is false info. In fact you do not even need a lot of PSI to do it.
Lastly, I have installed unoins on all my systems to remove backflow for winter. Prevents issues in winter etc.
I agree with what you read, but it is lacking in some important things. #1 is some XXscfm at WHAT PSI?The only source I know of with detailed information about blowouts it what I've read at http://www.irrigationtutorials.com/winter.htm.
According to the irrigation engineer that wrote these web pages (to help the DIY home owner) you need a MINIMUM of 20 sfcm to blow out a SMALL irrigation system (like 3/4" PVC). Even at that size, the author claims "And that is so small that it is not going to do a very good job!".
These are not my words... these are the words of an irrigation engineer.
This post has been edited 2 times, last edit by "debo" (Mar 23rd 2009, 1:14pm)
Again good read but that with a huge grain of salt, large then a horse. Again I nice read but app engs are not in the field.
PVB backflows in general don't need to be removed if you've winterized the system properly. personally, I like to remove RPZ backflows for customers for the winter. They have a high probability of not draining, and freezing and the replacement value alone dicates common sense. They are easily removed with two unions and stored inside. As for the PVB, you can either add unions, purchase a new backflow that comes with unions now (check out the Febco model). or, remove the top bell shaped cover and unthread the bonnet and popit as these are common stress parts over the winter. Just make sure you "regrease" the threads when you reinstall it. If you have a "blow out port" or "stop cock" below the backflow, keep it open for the winter.. this will allow any excess water to drain (however a proper winterization would leave none) and in the event someone recharges the sprinkler system by accident over the winter, the water will flow out before entering the backflow. As far as removing the entire thing, I don't feel that's neccessary.
FYI: I winterize my systems with 185 CFM towable compressors. I am able to open multi zones in one winterization. Watch the last head on the line for complete removal of water. Most Poly hose is rated to 100PSI, so I keep my compressors running around 90 to 95 PSI. Any more and you could potentially blow pipe apart.