Backflow occurs when contaminated water reverses direction and flows back into your clean water lines—putting your family’s health at risk and potentially causing costly damage. In this post, we’ll explain how backflow happens, why it’s dangerous, and what you must do to keep your home’s water safe.
What Is Backflow and Why Does It Happen?
Backflow is the unwanted reversal of water flow in your plumbing system. Two primary conditions cause it:
- Backpressure
When downstream pressure (from pumps, heaters, or elevated fixtures) exceeds incoming supply pressure. - Backsiphonage
When a sudden drop in municipal or well pressure (due to main breaks or heavy demand) siphons water back from fixtures or hoses.
Both scenarios can draw contaminants—fertilizers, soaps, sewage—into your potable water.
Health and Structural Risks of Backflow
- Contamination of drinking water with bacteria, chemicals, or sewage
- Illness from pathogens like E. coli and Legionella
- Corrosion and damage to pipes, fixtures, and appliances
- Code violations and fines if prevention devices aren’t installed or tested
Common Backflow Prevention Devices
| Device Type | How It Works | Typical Use |
|---|---|---|
| Air Gap | Physical separation between outlet and flood level | Dishwashers, utility sinks |
| Check Valve | One‑way valve that blocks reverse flow | Irrigation systems, booster pumps |
| Reduced Pressure Zone (RPZ) Valve | Spring‑loaded checks with relief port to discharge reversed flow | Commercial lines, industrial equipment |
| Pressure Vacuum Breaker (PVB) | Spring actuator opens vent on low pressure to admit air | Lawn irrigation, sprinkler systems |
DIY vs. Professional Backflow Prevention
Simple air‑gap installations at utility sinks are DIY‑friendly. However, most prevention devices (RPZ, PVB, check valves) require correct sizing, placement to meet local code, and annual testing by a licensed backflow tester.
Step‑by‑Step: Installing a Pressure Vacuum Breaker (PVB)
- Shut off downstream water and relieve line pressure.
- Mount the PVB on a solid wall, 12 inches above the highest downstream outlet.
- Connect inlet and outlet with recommended fittings and pipe sealant.
- Turn on supply slowly, checking for leaks.
- Adjust test cocks and note relief valve opening pressure.
After installation, have a certified tester perform the annual backflow test.
Preventing Clogs That Cause Backpressure
Blockages downstream can create backpressure that pushes water backward. To avoid this:
- Schedule routine professional video pipe inspections with CPR for Pipes.
- Keep lines clear with periodic mechanical cleanings.
When to Engage a Pro for Backflow Prevention
- You need backflow prevention device installation or testing with CPR for Pipes.
- You suspect hidden blockages causing damaging backpressure.
- You’ve experienced foul odors or contamination in your water lines.
Protect your home’s water supply by partnering with the experts at CPR for Pipes.