I’ve done a bunch of research and I cannot figure out if I need a backflow/filter/pressure reducer for each zone or if I can get away with having the backflow/filter/pressure reducer at the main valve (right at the hose spigot) and then just use a valve for each zone.
Here’s my setup:
My water source is a hose spigot which I measured at 378 gph.
I am planning to have three zones:
Zone 1 : Vegetable garden (consists of various rows of 12" spacing dripline, a total of 342’ of dripline)
Zone 2 : Grapes (currently 2 grape plants which will be fed by 12" spacing dripline)
Zone 3 : Shrubs (viburnum,hydrangea,dogwood,plum yew, various flowers for a total of 207’ dripline)
Could I set it up like this:
Hose spigot to backflow prevention, main valve, filter, pressure reducer then run about 15’ to get to my garden. Once in my garden I have 3 valves, one for each zone. Or would I need a filter/backflow/pressure reducer for each zone?
I don’t see much practical advantage to having a pressure reducer or back flow on each of your zones. Most drip setups that I’ve seen which connect at a hose bib rely on the backflow close to main connect and then they run and branch the dripline from there.
@jjbartoszek, here’s a great resource for designing and installing a sprinkler system. Only one backflow preventer, filter, and pressure reducer are needed for the entire drip system (assuming it’s a common residential application).
To my understanding, you will be attaching the water supply to the end of a hose spigot. Is this correct? Is there any way you can tap into the main water line of the house? Volume (378 gph) is an important number, but pressure is just as important. Do you happen to know the PSI? If you haven’t yet, the resource above will give you detailed instruction on how to take this measurement and factor it into the design of your system.
Thanks for the help. One follow up question: could you explain why some plans call for a $3 back flow preventer which screws onto the hose spigot, and others call for an $80 pvb? Can I get away with the $3 option for my setup?
Drip backflows that connect to a hose bib based drip setup are typically significantly cheaper than a PVB. About $5 is typical from what I’ve seen and should be fine if you’re coming off your house spigot. The $80 PVB is typically for setups connecting directly to main taps and so forth. $80 is actually a relative bargain… where I live code requires a $200 Febco even on residential irrigation!
If anybody wants to get into the details of designing an irrigation system (drip, sprinklers, simple, very complex etc) then I’ve found irrigationtutorials.com to be an unbelievable resource. If you read through all of it you’ll be more knowledgeable than 99% of irrigation contractors you come across.
@jjbartoszek & @craigjl, good evening. Very sorry for the slow reply to this thread.
I’d recommend a PVB over a drip backflow if you’re looking to install a long term system. If it’s just a hose for the summer or a temporary solution, then the drip backflow is sufficient.
Hope this helps. If you have any other questions, please don’t hesitate to ask.
I’m beginning to think the homeowners before me that installed the current irrigation system were idiots. Below ground anti-siphon (!) and no sign of an actual backflow preventer. (That’s not all they got wrong…) I’ve got some work to do after the watering season is over. Great website!
