Guide · Faucet head assembly
Backflow preventers on a drip faucet: what they are and who decides
What backflow and cross-connections are, why your water utility decides which device a drip faucet needs, the ASSE standards that exist, and what makers say.
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- Rain Bird HT07525PS 3/4 in FHT x MHT 25 psi pressure regulatorCheck price on Amazon
- Rain Bird PRF07530S 3/4 in MPT pressure-regulating filter (30 psi, 200 mesh)Check price on Amazon
- Rain Bird FCKIT‑1PK faucet connection kit (backflow preventer, 25 psi regulator, 150 mesh filter, tubing adapter)Check price on Amazon
Short answer
A backflow device keeps water in your garden lines from flowing back into your drinking water. Which device your connection needs is set by your water utility and local plumbing rules, not by a drip kit and not by us. Ask them before you choose one, and follow the device maker's instructions.
Picks in this topicSee the shortlist
- Rain Bird HT07525PS 3/4 in FHT x MHT 25 psi pressure regulatorCheck price on Amazon
- Rain Bird PRF07530S 3/4 in MPT pressure-regulating filter (30 psi, 200 mesh)Check price on Amazon
- Rain Bird FCKIT‑1PK faucet connection kit (backflow preventer, 25 psi regulator, 150 mesh filter, tubing adapter)Check price on Amazon
The terms
The US EPA defines a cross-connection as an actual or potential connection between a drinking water supply and plumbing that does not carry drinking water. It defines backflow as the unintended reversal of flow through a cross-connection.[1] The EPA also describes backflow as any unwanted flow of used or non-potable water back into the drinking water system.[2]
A drip system connected to an outdoor faucet is a connection of this kind. The EPA notes that cross-connections can occur between public water systems and private irrigation systems that receive their water.[1]
Why it matters
The EPA says backflow can occur when pressure in the distribution system falls below that of the connected plumbing.[1] Its fact sheet describes a case where an irrigation line connected without what the EPA calls an approved backflow prevention assembly let irrigation water flow back into a public water system.[1] That is one documented case, not a measure of how often it happens. The EPA recommends cross-connection control and backflow prevention programs.[2]
Who decides what you need
The EPA says cross-connection and backflow prevention programs vary by state and municipality. For more information it points to state drinking water programs, plumbing or building code authorities and health departments.[1]
In practice, start with your water utility. It can tell you what the local rules require at a hose faucet, and whether a device must be a particular type. We do not decide that, and neither does a kit's box.
Standards that exist
ASSE, a standards body, lists ASSE 1011-2023 for hose connection vacuum breakers and ASSE 1052-2023 for hose connection backflow preventers.[3] A hose connection vacuum breaker is one device type these standards cover.
A standard existing does not mean a product meets it. A product meets one only if its maker or a certifier says so for that exact model. Whether a given standard satisfies your local rules is again a question for your utility or plumbing authority.
What makers say about their own devices
These are maker statements, reported as such. None of them says a device meets any code.
- DIG D45. DIG lists its D45 backflow preventer with a 3/4 in female hose thread inlet and 3/4 in male hose thread outlet, for up to 100 PSI and 8 GPM.[4] DIG says the D45, a vacuum breaker, cannot be used under continuous pressure, and notes that some municipalities and water districts require such devices.[4]
- Mister Landscaper. It says a brass backflow device needs to be the first item attached to the faucet in its system.[5] It no longer offers its MLF-31 backflow valve and links to a brass device on Amazon as a suggested replacement.[5] That Amazon page is titled as an Eastman 3/4 in FHT x MHT brass hose bibb anti-siphon vacuum breaker, not a Mister Landscaper product.[6] We make no certification claim for it.
Is a hose bib vacuum breaker enough?
Ask your water utility. Requirements vary by state and municipality, per the EPA, and the answer depends on your connection.[1]
Why is my backflow preventer leaking?
Some devices are designed to release water. Mister Landscaper says its backflow prevention valve has relief holes to reduce pressure, and that some water draining from them is normal.[5] DIG says the vents on its D45 open when supply pressure drops.[4] For any other device, check its maker's instructions. If water keeps running, ask the maker or your utility.
Do not block those openings. Rain Bird's winterizing instructions warn not to block the air vents and drain outlets on backflow preventers.[7]
Continuous pressure
DIG says its D45 cannot be used under continuous pressure.[4] Where a timer or shut-off sits after such a device, follow the device maker's placement instructions. The faucet head assembly guide shows one maker's documented order.
Next
Questions
Do I need a backflow preventer for drip irrigation?
Your water utility or local plumbing authority decides. The EPA says cross-connections can occur between public water systems and private irrigation systems, and that prevention programs vary by state and municipality.[1]
Is a hose bib vacuum breaker enough?
Ask your water utility; we do not decide. ASSE lists a standard for hose connection vacuum breakers (1011-2023) and one for hose connection backflow preventers (1052-2023), but local rules set which applies.[3][1]
Why is my backflow preventer leaking?
Some devices release water by design. Mister Landscaper says its valve's relief holes drain some water normally; for other devices, check the maker's instructions, and do not block vents or drains.[5][7]
Who do I ask about backflow rules?
Start with your water utility. The EPA also points to state drinking water programs, plumbing or building code authorities and health departments.[1]